AVENTURINE GLAZES 
 
 BY 
 
 JOHN SHERMAN LATHROP 
 
 THESIS 
 
 FOR THE 
 
 DEGREE OF BACHELOR OF SCIENCE 
 
 IN 
 
 CERAMIC ENGINEERING 
 
 COLLEGE OF ENGINEERING 
 UNIVERSITY OF ILLINOIS 
 
 1922 
 
•-Mil 
 
 Digitized by the Internet Archive 
 in 2015 
 
 
 https://archive.org/detaiis/aventurineglazesOOIath 
 
INDEX 
 
 Page 
 
 I Introduction . . • . o 1-5 
 
 II Work Conducted by Previous Experimenters 6-7 
 
 A, Work done by U.S. Bureau of Mines 6 
 
 B. Work done by Nathan Bromberg 6-2> 
 
 III Scope of Present Investigation S 
 
 IV Method of Investigation S-9 
 
 V Burning 9 
 
 VI Method of Preparing Glazes 10 
 
 VII Materials Used 11 
 
 VIII Trial Pieces 11 
 
 IX Effect of Variations in Al20^, FegO^. . . • 11-2S 
 
 Ao First Series 11-20 
 
 B. Second Series 21=-24- 
 
 C. Third Series 24-27 
 
 D. General Conclusions from First Part 27-28 
 
 X Effect of Variations in Na20, K 2 O, CaO and PbO . . . 2S-3^ 
 
 A, Conclusions from Second Part 28-3^ 
 
 XI General Conclusions drawn from Experiments on 
 
 Aventurine Glazes 34-35 
 
INDEX TO FIGURES 
 
 Page 
 
 Fig, I Time -temperature Curve for Aventurine 
 
 glazes Maturing at Cone 1 l4a 
 
 Fig. II Area of Investigations of Variable Con- 
 
 stituents of the Aventurine Glazes 
 of Part 1 12a 
 
 Fig. Ill Chart showing location of all Glazes on 
 Tri-axial chart together with Dia- 
 gramatic Presentation of Results .... 12b 
 
 Fig, IV Time-temperature Curve for Aventurine 
 
 Glazes burned at cone 3 24a 
 
 Fig, V,VI,VII,VIII,IX Presentation of the R 0 
 components of each glaze together 
 with the location of each glaze 
 on Tri-axial diagrams for glazes 
 varying in the R 0 components 29a-29e 
 

STUDIES IN AVENTURINE GLAZES, 
 
 I 
 
 Introduction 
 
 Of all the types of glaaes, probably the most beautiful and 
 yet the most difficult to produce are the crystalline glazes. 
 
 There has been very little technical research done on this subject 
 and undoubtedly if more work were done on the subject and more in- 
 formation were available, crystalline glaaes could be produced and 
 controlled as easily as other glazes. The glaze composition, the 
 heat treatment of the glaze, and the body composition, are factors 
 which have to be studied for each particular glaze. 
 
 There are two typos of crystalline glazes^;- The first type, 
 the macro-crystalline glazes, includes the aventurine glaze, some- 
 times called "goldstone" or "tiger eye". In this type the crystals 
 separate out of the molten matrix on cooling of a size readily vis- 
 ible to the maked eye. The second type, the micro-crystalline 
 glazes, includes some of the mott glazes. In this type, the entire 
 mass crystallizes. For developing aventurine glazes, Stull recom- 
 mends applying metallic oxides to the body and covering this with 
 a boric acid glaze. When the glaze fuses and becomes fluid, it 
 takes part of the metallic oxide into solution and, if enough of 
 it is dissolved, the glaze becomes supersaturated and crystals se- 
 parate out on cooling, 
 
 p 
 
 Mellor^ has given a good explanation of the formation of 
 cyrstalline glazes by comparing the molten matrix with ordinary 
 
 ^ R, To Stull "Notes on the Production of Crystalline Glazes". 
 
 Trans, Am. Cer, Soc, Vol. VII, 190^ p,lS 6 
 
 J , W. Mellor "Crystallization in Pottery". 
 
 Trans. Eng, Cer. Soc. Vol. IV, 1902 p .52 
 

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 solutions as follows: "The molecules of the solution resist crys- 
 tallization and some crystallizing force is required to start crys- 
 tallization." 0stwald3 states that it is only necessary to have 
 one millionth part of a milligram in a solution of sodium chloride j 
 to overcome the passive resistance of the molecules and start crys- 
 tallization of the sodium chloride. Stull^ , in comparing the 
 crystallizing tendencies of various oxides draws the following con- 
 clusions! - 
 
 I. The strongest crystallizing tendencies are given to 
 glazes by those chemical elements of low atomic weight whose 
 oxides go to make up the R 0, such as sodium, potassium, mag- 
 nesium, calcium, manganese, iron zinc, etc. 
 
 II. Those metals of high atomic weight, such as barium, 
 lead, etc., seem to impart a glossy nature to silicates when 
 used in sufficient quantities, which is unfavorable to crys- 
 tallization. 
 
 III. Those chemical elements of higher atomic weight whose I 
 oxides make the acid portion of a glaze such as silicon, titan-J 
 ium, phosphorus, etc., produce the best crystallizing agents, 
 while those of lower atomic weight, as for example, boron, 
 having an atomic weight of 11, impart a fluidity and brilli- 
 ancy to a glaze which is detrimental to crystallization. 
 
 IV. The introduction of an R20^materially assists crystalli- 
 zation in some cases, while in others it is detrimental to it, 
 
 3 Zeit. Phys. Cehm. 1S97, 22, 2S9. 
 
 Ibid 1. Vol. VI., p. Igg. 
 

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 ^The name "Aventurine" as applied to glazes, originated from 
 its similarity to certain types of quartz and feldspar spangled 
 with scales of mica, hematite or gothite, They give off fire-like 
 reflections when held in a bright light and are known as aventurine | 
 feldspar and aventurine quartz. ! 
 
 i 
 
 Wohler 6 produced glazes having a similar appearance in lS^ 9 o | 
 Wartha? obtained an aventurine effect by first applying an engobe o 
 iron or uranium oxide and then covering the same with a borax 
 glaze . 
 
 Aventurine gla.zes are produced by mixtures in which there is 
 an excess of metallic oxides which go into solution. The glaze 
 matrix becomes saturated with the metallic oxide, and on cooling, 
 the solvent capacity of the glaze reaches a maximum, the glaze be- 
 comes supersaturated, and the excess gradually separates out in 
 thin, plate-like crystals. The metallic oxides generally used in 
 aventurine glazes are those of iron, chromium, and sometimes copper 
 
 C6 
 
 Mellor*^ states that aventurine glazes are more easily obtained on 
 red tile than on white tile. This is probably due to the fact that 
 the glaze dissolves some iron oxide from the body and aids in satur 
 ating the glaze. Stull^ advises the use of vitrified bodies which 
 have been biscuited at a temperature of two or three cones higher 
 than that of the glaze. 
 
 Zimmerl^states that it is necessary to have; IM^.^ a continu- 
 ously oxidizing fire; 2 ^^, a gradually increasing temperature; 
 
 ^ H. G. Schurecht — Journal Amer. Cer. Soc., Vol. 3# No. 12 
 
 6 Thomind, Ztg., 1^96, p. 219- December, 1920. 
 
 7 Ibid, 1^90 p. 170 . 
 
 ^ Zeit. Phys. Chem. 1S97, 22, 2S9. 
 
 9 Ibid 1, 
 
 W. H. Zimmer. ^^Crystallized Odagea". Trans .Am. Cer .Soc «Vol .14-1912 .| 
 
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3^ , a gradually decreasing tempeirature; and exclusion of 
 
 Al20^ from the glaze# The rates of crystallization of the differ- 
 ent glazes vary so much with the tempera^ture that the rate of cool- 
 ing after burning must be regulated to suit the glaze. Correct 
 cooling is of as much importance as is correct composition. The 
 purpose of the slowly cooling fire is to give the crystals time 
 to grow. 
 
 Most writers are of the opinion that the "aventurine effect" 
 is best produced by introducing iron in a suitable form into a 
 properly constituted glaze. Mackler determined the effect of 
 increasing the iron oxide content in glaz«s of the cone 09 type 
 and found that when 35 parts of iron oxide were added to 100 parts 
 of glaze, he obtained an aventurine effect, but the color of the 
 glaze was too dark, due to the reduct ioh of the iron oxide to the 
 ferrous condition. He, therefore, tried 20 per cent of finely 
 ground metallic iron and obtained a transparent yellow glaze with 
 many gold-like crystals. The glaze used by him corresponded to the 
 following formulas- 
 
 0.25 KoO ) 
 
 ) 2.25 SiOp 
 
 0.25 Na 0 ) 
 
 2 ) 0.75 BgO, 
 
 0.50 CaO ) 
 
 PatrikjlB produced artificial crystals of hematite by melting 
 a mixture of iron sulphate and sodiuun chloride and dissolving in 
 water. Crystals 1 to 2 mm. in diameter were produced in this 
 manner. These cyrstals are not easily dissolved in the glaze melt 
 
 Thonind, Zeitg., IS96, p. 219. 
 
 Ibid 11, 1 S^ 6 , p. 275. 
 

 
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 and when introduced into 
 
 a glaze appear as bright scales 
 
 similar 
 
 to aventurine glaaes. 
 
 
 
 
 
 The following are two formulae 
 
 for aventurine glazes 
 
 8Ub“ 
 
 mitted by Parmelee^^ and reported as giving good golstone 
 
 glazes:- 
 
 
 Cone 2 glaze 
 
 Fritt for cone 
 
 2 glaze 
 
 0.10 K «0 
 2 
 
 
 
 0.2 KpO ] 
 
 
 
 0,15 NapO! 
 
 f 
 
 
 0.3 NapOJ 
 
 
 
 
 0 o 22 A 1 0 
 
 
 d ' 
 
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 0.25 I 
 
 2 3 
 
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 0,2 CaO 
 
 
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 0 .30 BpO-z 
 
 
 ' 
 
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 ) 
 
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 0,15 FeO ) 
 
 
 0.2 PbO ; 
 
 
 
 0.1 FeO 
 
 1 
 
 
 Batch Weights 
 
 
 Batch weights for fritt 
 
 Fritt 
 
 
 14-1 
 
 Feldspar 
 
 
 111 
 
 Whiting 
 
 
 
 Borax 
 
 
 115 
 
 White load 
 
 65 
 
 Whiting 
 
 
 20 
 
 China clay 
 
 31 
 
 White lead 
 
 52 
 
 Flint 
 
 
 64 
 
 Flint 
 
 
 4 S 
 
 Red iron 
 
 oxide 
 
 6 
 
 Red Iron 
 
 oxide 
 
 S 
 
 Cone 09 glaze 
 
 
 Fritt 
 
 for Cone 09 
 
 glaze 
 
 0.40 NagO) 
 
 
 0.5 NapO) 
 
 ) 0.4 BpO,) 
 0.4 PbO ) ^ 
 
 2,0 SiOg 
 
 ) 0.03 AlpO,) 
 0.46 PbO ) 
 
 2.1 SiOp 
 
 0.14 FeO ; 
 
 0.32 BpO^ ) 
 
 d 
 
 
 
 
 
 
 
 
 
 Batch Weights 
 
 
 Batch weights for fritt 
 
 Fritt 
 
 
 220 
 
 Borax 
 
 
 76 
 
 Red lead 
 
 
 32 
 
 Sodium carbonate 
 
 32 
 
 Red iron 
 
 oxide 
 
 5 
 
 Red lead 
 
 
 91 
 
 Ball clay 
 
 S 
 
 Red iron 
 
 oxide 
 
 S 
 
 Flint 
 
 
 24 - 
 
 Flint 
 
 
 120 
 
 • 13 
 
 Professor C. W. Parmelee, Cer . 
 
 Dept ., University of Illinois. 
 
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- 6 - 
 
 II 
 
 Discussion of Previous Investigations. 
 
 l^In experiments conducted by the Bureau of Mines, the effect 
 
 of varying iron oxide and silica was studied between the following 
 
 limits in a cone 4 aventurine glaze: j 
 
 0.05 AlpO, ) 
 
 0,4- Na«0 ) ^ i 
 
 ^ ) 0.25 BpO^z I 2A » 4,2 SiO„ 
 
 0.6 PbO ) ^ ^ 
 
 0.12-0. SI Fc 203) 
 
 A, Summary of Work done by the U.S. Bureau of Mines 
 
 1. Within the foregoing experimental limits aventurine glazes 
 were obtained with more than 0.4-1 Fc20j in glazes containing 
 
 2.4- Si02# and with more than 0.5S Feg 0^ in glazes containing 4-. 2 
 Si02 a 
 
 2, Glazes with 0.4-1 to 0*73 FepO^ vary in color from red to 
 black according to kiln conditions, red being produced under oxi- 
 dizing conditions and black under reducing conditions. 
 
 3* With reducing conditions the glazes high in iron become a 
 dull black with a metallic lustre. By applying a thin coating of 
 accone 02 lead glaze on the surface of such a glaze and firing in an 
 oxidizing atmosphere, a maroon effect is obtained. 
 
 4-. Increasing the iron content increases the size and mmiber 
 of crystals and also the refractoriness of the glazes. 
 
 B. Work done by Nathan Bromberg on Thesis for B.S. Degree 
 in Ceramic Engineering, University of Illinois, 1915* 
 
 The purpose of this study was to develop aventurine glazes 
 which would mature at cone 010 (950° C) , cone 1 (1150° C) and 
 cone 5 (1230*^ C). The field to be investigated was determined on, 
 
 iT — — - 
 
 Ibid 5. 
 

 [i 
 
 f 
 
 r ^ 
 
 . irv 
 
 * » : : 
 
and a rectangular diagram drawn so as to include all the variations 
 desired. 
 
 Bromberg’s General Conclusions. 
 
 From the results of the foregoing studies, the following con- | 
 
 ! 
 
 elusions may be drawn: 5 
 
 1. The formation of crystals depends upon the slow cooling 
 of the glaze. As each glaze has a different rate of crystal- 
 lization at each temperature, the cooling curve for each glaze 
 should be determined individually* 
 
 2. The amount of Fe^O^ necessary for the formation of aven- 
 turine crystals depends upon the glaze and may vary from 0.25 
 to 0.6 molecules. 
 
 3. Increasing the Na^O content increases crystallization. 
 
 4. Aventurine crystals may be formed in the presence of .2 
 molecules of A1_0^. 
 
 5 . Aventurine crystals may be formed in the presence of 
 CaO even when there is as much as 0.4 molecule present, 
 
 6* Decreasing the lead, increases crystallization and de- 
 creases the gloss. Crystals were obtained in the presence of 
 0.5 molecule of PbO. 
 
 7 . These aventurine glazes did not seem restricted to any 
 particular molecular or oxygen ratio, but came within the 
 limits of good glazes. 
 
 
' . 1 . ' 
 
 ' 'I 
 
 '\r 
 
 I. 
 
 * 
 
 I 
 
 A » 
 
 * 
 
 \ 
 
Ill 
 
 Scope of Present Investigation. 
 
 In the present investigation an attempt has been made to study 
 the effect of variations in the alumina, ferric oxide, boric acid, 
 and R 0 members in a cone 1 aventurino glaze. The correct heat 
 treatmtnt for the proper development of the aventiirine effect was 
 also studied as a means of control of the crystal growth. 
 
 lected as a basis of the study. The investigation was divided into 
 two parts. In the first part the effect of variations in the alum“ 
 ina, boric acid, and ferric oxide content, and the effect of differ 
 ent heat: treatments were studied. For the second part of the in- 
 vestigation, the best aventurine glaze developed in the first part 
 was used as a basis for the investigation of variations in the RO 
 constituents of the glaze. 
 
 The formula of the glaze under investigation with all the 
 variables indicated is as follows: - 
 
 were varied; the R 0 was kept constant at 1,0 Na 20 . The series was 
 divided into three groups; the first group contained 0.05 nioles 
 of Alumina; the second group contained 0.10 moles of Alumina; and 
 the third group contained 0 .I 5 moles of Al^amina. Each group was 
 
 IV 
 
 Method of Investigation 
 
 A good aventurine glaze maturing at cone 1 (1150^ C) was se~ 
 
 0,0 to 1.0 NagO) 
 
 0.0 to 1.0 K^O 
 0,0 to 1.0 CaO 
 0,0 to 1.0 PbO 
 
 For the first part of the experiment only the ^ 2^3 
 

 i; 
 
 
 f 
 
 I 
 
 t 
 
- 9 ' 
 
 divided into a rectangular field with four horizontal members rep- 
 resenting variations in 62 ©^ content from 1,25 moles to 2.0 moles, 
 and five vertical members representing variations in the Fe^O^con- 
 tent from 0*75 moles to 0*95 moles. 
 
 V 
 
 Burning 
 
 All the trials were burned in glazed saggars in a down-draft 
 coal-fired kiln, described in University of Illinois Bulletin, num- 
 ber 20, Vol. XI, #44. The first burn was conducted following the 
 time temperature curve of Fig. 1 so that there was a considerable 
 temperature difference throughout the kiln. Cone pads were placed 
 in each saggar so that the heat treatment of each trial could be 
 noted. The effect of temperature variations was in this manner 
 closely studied. The next biirn was conducted at cone 3 (1190° C) 
 and the final burn was conducted at cone 1 with uniform heat treat- 
 ment throughout the kiln as far as possible. 
 
 In the second part of the work the variations were made in the 
 R 0 members as already shown and the trials burned to cone 1, A 
 representation of the field covered by four variables is difficult 
 to place on paper but a visual representation of the field is of a 
 pyramid with a triangular base. At the apex of the pyramid, 1.00 
 Na20 is located with 1.00 KgO, 1.00 CaO, and 1,00 PbO as the three 
 corners of the base of the pyramid. To give a clearer conception 
 of the field covered, I have drawn up a series of tri-axial diagrami 
 representing horizontal planes parallel to the base of the pyramid 
 which indicate clearly the variations in the R 0 members. 
 
 These glazes were burned to cone 1 in glazed saggars as before 
 
 and the effect of the variable RO members was noted and tabulated 
 
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- 10 - 
 
 VI 
 
 Method of Preparing Glazes j 
 
 For the first burn of the first part of the investigation and | 
 for the second part, all the glaze materials were fritted as it ! 
 takes a long time for the glaze to assimilate all the materials, ana 
 better aventurine glazes are produced if all chemical action has c 
 ceased before the final fusion of the glaze. For the second and 
 third burns of the first part, O 0 O 5 moles of alumina were omitted 
 from the fritt and added as raw clay in an endeavor to take advan- 
 tage of the plasticity of the raw clay to aid in keeping the fritt 
 in suspension. 
 
 As most of the glaze is quite fluid before all of the more , re- 
 fractory materials of the glaze are entirely dissolved, the method 
 of drop-fritting the glaze was not employed. The materials were 
 fritted in closed bottom crucibles to a quiet fusion and then poured 
 into cold water for quenching. 
 
 After quenching, the fritts were ground in porcelain ball mills 
 with water till they readily passed a 100 mesh screen. To keep the 
 fritt in suspension in water, the best method devised was to satur- 
 ate the suspension with aqueous ammonia while still in the ball mill, 
 Using this method no difficulty was experienced in suspending the 
 fritt in water. 
 
 In the first part of the investigation, the four corner fritts 
 of groups I and III were prepared as described and all the inter- 
 mediate glazes were prepared by molecular blending. This method of 
 blending is described by Purdy and Fox in their work on fritted 
 
 glazes. ^5 in the second part, the four corner fritts of the pyra- 
 
 15 R. C. Purdy and H. B. Fox "Fritted Glazes”. Trans. Amer, i 
 
 Cer, Soc, Vol, IX, 1907 P. 9S. 
 
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-11- I 
 
 raid were prepared and the intermediate glazes were blended in the 
 same manner as for the previous group, 
 
 VII 
 
 Materials Used 
 
 The following potter’s materials were used for making the 
 glazes and their formulae calculated as shown! | 
 
 Clay - English china clay #3 - AlgO^ .ESiOg «6HgO 
 Borax - Na^B^O^lO H^O 
 Boric Acid - BgO^. 3^2® 
 
 White Lead - Pb (0H)2 - 2 PbCO^ 
 
 Whiting - Ca CO^ I 
 
 Soda Ash - Na2C0^ 
 
 Potassium Carbonate - K^CO^ 
 
 Ferric Oxide - Fe20^ 
 
 VIII 
 
 Trial Pieces 
 
 The trial pieces were rectangular biscuit tile 1 1/2" x 3" 
 manufactured by the U, S, Encaustic Tile Company of Indian^-polis , 
 Indiana* 
 
 IX 
 
 First Part^^ 
 
 AVENTURINE GLAZE -Cone 1 
 
 The variations in the type formulae of all the glazes of the 
 first part are as follows:- 
 
 I 0.05 - 0*15 AlgO^j 
 1 Na20 I 1.25 - 2,00 B20^ | 7«00 Si02 
 
 ( 0.75 - 0.95 Fe203) 
 
 An experiment conducted by the Ceramics 5 class. University of I 
 Illinois, in the first semester of 1921-22, (Summary by J . S . Lathrop ) , 
 
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- 12 - 
 
 There are three groups of glazes prepared as follows;- 
 
 Group I 0.05 Al 20 ^ 
 
 Group II 0.10 ” 
 
 Group III—— 0.15 " 
 
 All groups used 1.00 NagO and 7*00 constant and varied as 
 
 follows in B20^and Fc20^ 
 
 R C 
 
 Fe20^ 
 
 0.95 
 0.90 
 0.89 
 
 0 . 60 
 
 0. 79 
 
 The figures at the left 
 and bottom indicate the moles 
 of oxide and the letters at t 
 the top with the figures at 
 the bottom and the group num- 
 ber locate the glaze as IIC 4 , 
 IIIB5, etc. 
 
 1.29 1 .90 1 . 79 ^*00 
 
 Bp. 
 
 The tri-axial diagram. Fig. II, shows the small area of Avsn- 
 turine Glazes figuring Al20^plus B20^ plus Si02 as equal to 1 . The 
 diagram. Fig. Ill, which is an enlarged diagram of the portion of 
 the tri-axial diagram of the area of the Aventurine Glazes gives 
 the location of each glaze together with the results of the glost 
 burn in diagrammatical form. 
 

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- 13 - 
 
 FRITT FORMULAE and COMBINING WEIGHTS 
 
 lAl 
 
 ia6 
 
 IDl 
 
 1 D 6 
 
 IIIAl 
 
 IIIA6 
 
 Proportion 
 
 Pa rt s 
 
 Comb • 
 Weight, 
 
 0,05 Clay — 52.0 — 11.10 
 
 0.625 Borax— 954-.0 — 126.00 
 
 0.375 Soda Ash—— — I59.O — 23.25 
 
 0.950 FepO^ 6OS.O — — 152.00 
 
 6,900 Flint — 1656. 0 — . 4 - 14.0 0 
 
 3W.0 7^5 
 
 
 0.05 Clay- — — 52.0 
 
 0.625 Borax 954.0 
 
 0.375 Soda Ash— 159.0 
 
 0.750 FepO^— — 4 S 0.0 
 6.900 Flint———— 1656.0 
 
 34^.0 
 
 11.10 
 
 126.00 
 23.25 
 
 120.00 
 414.00 
 
 0.05 Clay 52.0 — — 
 
 1.000 Bora,x — I52S.O — 
 
 0.950 FepO-z-^ — * — 6OS.O - — — — 
 
 6.900 Flint- 1656.0 
 
 3 S 44.0 
 
 11.10 
 
 202 .90 
 
 152.00 
 
 414.00 
 779.10 
 
 0.05 ’Clay — 52.0 11.10 
 
 1.000 Borax — I52S.O 202,00 
 
 0.750 FesOx 480.0 — 120.00 
 
 6.900 Flint' 1656.0 — — 414.00 
 
 3716.0 T^TTio 
 
 0.625 Borax 954.0 
 
 0,375 Soda Ash — 159.0 
 
 0.150 Clay— 155.0 
 
 0.950 FepO:: 6OS.O 
 
 6.700 Flint 1 608.0 
 
 3463 .0 
 
 126.00 
 23.25 
 33.30 
 
 152.00 
 
 402.00 
 
 73^^55 
 
 0,625 Borax — 954.0 
 
 0.375 Soda Ash I59.O 
 
 0.150 Clay— 155.0 
 
 0.750 Fe«0, 480,0 
 
 6.700 Flint — — 16O8.O 
 
 335^0 
 
 126.00 
 23.25 
 33.30 
 
 120 .00 
 
 402.00 
 
 704.55 
 
• AI '■ 
 
 J- 
 
“l4-“ 
 
 Proportion Comb. 
 
 IIIDl 
 
 1.00 
 
 Borax — ^ — — 
 
 
 0.15 
 
 Clay — 
 
 
 0.95 
 
 FcpO -7 — — — — — 
 
 
 6.70 
 
 Flint-——-— 
 
 IIID6 
 
 1.00 
 
 Borax — — — - — »»»— 
 
 
 0.15 
 
 Clay — — — 
 
 
 0.75 
 
 FcpO -7 
 
 
 6.70 
 
 Flint——— 
 
 Parts Weight . 
 
 152s .0 — 202.00 
 
 155.0 — 33.30 
 
 605.0 - 152.00 
 
 160s. 0 — te .00 
 
 3 ^ 99.0 7 ^ 9.30 
 
 1525.0 — — — 202,00 
 
 155.0 — — 33,30 
 
 450.0 120.00 
 
 l6g0.0 402.00 
 
 3771.0 757.30 
 

 
 -15- 
 
 RESULTS OF GLOST BURN Cone 1. 
 
 Glaze 
 
 Cone 
 
 Description of glaze 1 
 
 1 
 
 3 
 
 Over-fired, dull, copper colored. 
 
 2 
 
 OS 
 
 Under-f ired, dull , yellow colored, crazed. 
 
 3 
 
 OS 
 
 " , " , yellow-red color, " . 
 
 IL 
 
 OS 
 
 ” , " , copper colored, crazed. 
 
 3 
 
 3 
 
 Over-f ired,bright jbrownish-black color. 
 
 6 
 
 OS 
 
 Under-f ired, dull, yellow-red color, crazed, j 
 
 7 
 
 3 
 
 Over-fired,bright, mottled brown color. 
 
 S 
 
 3 
 
 Over-fired, " ,dark maroon color. 
 
 9 
 
 3 
 
 " , " , Brownish-black color. 
 
 10 
 
 OS 
 
 Under-f ired, dull ,brick-r ed color , 
 
 11 
 
 3 
 
 Bright, deep brown color, few aventurine spangles. 
 
 12 
 
 3 
 
 Bright , black, speckled aventurine separations. 
 
 13 
 
 3 
 
 Bright , brown-black. 
 
 14 
 
 3 
 
 Matt texture , reddish-brown color. 
 
 15 
 
 3 
 
 Ower-f ired, dull , copper color dappled with black.. 
 
 16 
 
 3 
 
 Matt texture,copper color , bubbled, heavy aventur- : 
 ine separation. 
 
 17 
 
 3 
 
 Matt eggshell texture , dappled brown and copper 
 color. 
 
 IS 
 
 3 
 
 Matt texture, copper colored. 
 
 19 
 
 3 
 
 n tt n 
 
 » ® 
 
 20 
 
 OS 
 
 Dull, dirty yellow color, crazed. 
 
 21 ' 
 
 05 
 
 Bright , transparent , yellow, white bubbly separa- 
 tions on the surface. 
 
 22 
 
 06 
 
 
 i 23 
 
 o6 
 
 n 
 
 24 
 
 o6 
 
 " deeper yellow color. 
 
 25 
 
 03 
 
 ” yellowish brown color. 
 
 26 
 
 5 
 
 Bright , yellowish brown color , bubbled, crazed. 
 
!- 
 
 C' 
 
 I 
 
 X 
 
 
 
 rf»( 
 
 
 
 t 
 
 
 •r 
 
 r 
 
 \ 
 
 0 ::; 
 
 
 

 
 - 16 - 
 
 Glaze 
 
 Cone 
 
 Description of Glaze 1 
 
 27 
 
 5 
 
 Bright , brownish-black color, mottled effect* 
 
 2S 
 
 05 
 
 Bright, yellow color* 
 
 29 
 
 05 
 
 Bright, brownish yellow color. 
 
 30 
 
 03 
 
 " , yellowish brown color, pinholed, j 
 
 31 
 
 02 
 
 Bright, dark brown with aventurine separations, 
 pinholed. 
 
 32 
 
 02 
 
 Bright, mahogany color, little aventurine , crazed. 
 
 33 
 
 05 
 
 " ,dark yellow color, crazed. 
 
 3^^ 
 
 05 
 
 ", " , " , bubbled. 
 
 35 
 
 01 
 
 ", " » ^ > pinholed. 
 
 36 
 
 2 
 
 Bright, deep purple color , checkered in glaze ef- 
 fect, very fine aventurine , pinholed, cracked. 
 
 37 
 
 02 
 
 Bright, black color with heavy separations of 
 copper colored aggragates. 
 
 3S 
 
 02 
 
 The same with less metallic separations. 
 
 39 
 
 4 
 
 Bright , reddish-black color with white,bubbly 
 separations , 
 
 40 
 
 01 
 
 Bright , yellow color , bubbled. 
 
 41 
 
 05 
 
 Bright , yellow color, red aventurine only on 
 thin edges , crazed. 
 
 42 
 
 05 
 
 n 
 
 
 05 
 
 Bright , reddish-brown color, filled with very 
 Minute aventurine separations , crazed. 
 
 44 
 
 01 
 
 The same with larger aventurine separations. 
 
 ^5 
 
 2 
 
 Bright, brown color, heavy with aventurine separa-J 
 t ions , beautiful red and gold aventurine 
 spangles around the edges. 
 
 46 
 
 05 
 
 The same except that the color is darker. 
 
 1^7 
 
 05 
 
 The same. 
 
 4S 
 
 05 
 
 Bright , orange color, very heavy and minute aven- 
 turine separations , crazed. 
 
 49 
 
 2 
 
 Bright, dark purple color with one patch of 
 
 beautiful red and gold aventurine spangles. 
 
 50 
 
 01 
 
 Dull, the greater part of the piece red and full 
 of true goldstone spangles. 
 
 51 
 
 05 
 
 True matt texture , purplish-pink color, evident- 
 ly a micro-crystalline structure. 
 
A* * 
 
 ^'- 
 
 ■ 
 
 tf 
 
 Si. 
 
 4k 
 
 > 
 
 t 
 
 
 
 
 ri 
 
 " • '.;<7 
 
 .^0 
 
 . ... ^ . 
 
 ' 1 . . _ 
 • ■’ j '- • i , <11 ii;yc 
 
 * 4 » ... t» . . • ■ ; 
 
 ^ fti/ % «» ^0 
 
 '.' ' • • V. j, »a ll, \ £ 
 
 
 'V"'' 
 
 
Glaze 
 
 Cone 
 
 52 
 
 0 $ 
 
 53 
 
 04 
 
 5^ 
 
 01 
 
 55 
 
 01 
 
 56 
 
 05 
 
 57 
 
 05 
 
 5S 
 
 05 
 
 59 
 
 01 
 
 60 
 
 04 
 
 -17“ 
 
 Description of Glaze 
 
 The same but with more of the appearance of 
 aventurine spangles in the glaze. 
 
 The same but lighter in color. 
 
 Bright , yellowish-brown color with heavy aven- 
 turine spangles around the edge and few 
 inside^ crazed. 
 
 Bright, yellow color, aventurine on edges, 
 crazed. 
 
 Bright, deep brownish-purple color with very 
 minute and finely divided aventurine 
 spangles, not crazed and a very attractive 
 glaze. 
 
 Matt texture but in other respects the same 
 as glaze 5^ a- niuch lighter shade. 
 
 The same except a blighter finish and darker 
 color. 
 
 Bright , yellow color , heavy aventurine on the 
 
 edges and very few spangles inside , crazed. 
 
 Bright , light yellow color and very few aven- 
 turine spangles , crazed. 
 
 The diagram below show the three groups of glazes with the 
 different areas marked off on them. 
 
 Group I 
 0.05 AlgO^ 
 
 Group II 
 0,10 AlgO^ 
 
 Group III 
 0.15 Al^O^ 
 
 B 
 
 C B 
 
 No 
 
 ffych- 
 
 / 
 
 ■GO 
 
 
 
 y/es. 
 
 
 of 
 
 
 
 
 ?s 
 
 1 .2^ 1 .30 1 .13 2.00 
 
 2 3 
 

 
 ,-./o 
 
 ^'9 
 
 111 i . 
 
 .\.a ^ . 
 
 [s 
 
 
 
 I 
 
 i • X « 
 
 w 
 
 ... .‘V i.r' 
 
 -1. . 
 
 ‘ 
 
 I 
 
 f 
 
 « «■ 
 
 i 
 
 ( 
 
 1 
 
 ,L. 
 
 I 
 
 L 
 
 
-IS- 
 
 Discussion of Results 
 
 These results indicate that with this glaze composition, an 
 alumina content of 0,15 equivalents produces better conditions for 
 the development of aventurine glazes than does a lower alumina con- 
 tent, The results also indicate that the higher alumina content 
 produces more easily fusible glazes than do the lower alumina con- 
 tents. This may seem contradictory to ordinary experience but the 
 results point to this conclusion. 
 
 The glazes with 0*05 equivalents of alumina showed no aven- 
 turine tendencies at all. This may be due to the heat treatment 
 which they received; all of these glazes were burned either too 
 high or too low. However, some of the other glazes with a higher 
 alumina content which were burned either excessively high or ex- 
 cessively low showed brighter glazes and contained aventurine 
 spangles. One glaze alone in this group showed tendencies towards 
 the development of aventurine effects and that was the one highest 
 in boric acid and highest in iron oxide. This glaze only showed 
 the spangles under the electric light and was dull and unsatisfac- 
 tory. 
 
 The aeea of high iron oxide and mediiam boric acid content 
 with low alumina gave bright brown or black colored glazes which 
 lost their gloss on contact with the air. 
 
 The group of glazes containing 0,10 equivalents of alumina 
 developed all bright glazes. In this group only the glazes highest 
 in iron oxide and highest in boric acid showed any separation of 
 the iron from the glaze. In some of these glazes, the separation 
 was thin, minutely divided aventurine spangles but in one glaze, 
 number 37 j i't separated as large metallic separations which gave a 
 

 
 
 ■ 1 0 ‘.;“. •■ 
 
 ■ f • r^*‘ 1 ' T' , * i*f • 1 
 
 • V' • VA J ♦ » t.' , 0 . ,i, i . y •• 
 
 u'v '.»>• 1.0 i.:nt 
 
 ^ %« 
 
 
 
 vijp‘ -'X, “ 
 
 
 .i' 'i'; . 
 
 ’ i 4 „’ • rrrrf: ,o» w,.ii ., 
 
 r- : . t "..■.» V? il« V Ak 
 
 
 
 ! i- '••-'f -Jjl.-'J '■*1 
 
 -.1 
 
 
 ‘ AiVtaujt/ 
 
 . 1 1 cs.r ';.r, \ v 
 
 f!ci j:.d i ■!■: ■ .K : \':.i r;t*i • u- 
 
 SiDix* : '. iZ‘ ": Vli^g' .■ fcftSbtlC ,! 
 
 t 
 
 -->CJvjc» oc X'9»'Cr!'; iini.'ju'j.. *c k:, < : v i, pc 
 
 . ■ .’,-bp e f? oc r..‘:; t.:' yoA; 
 
 . ii;. -oj’’-o .- i:?; i.-r oei ‘i 
 
 '11 i cc fu'-*' ■/’' ' ! 
 
 . r .:>3 »<ii'iUu j| 
 
 ' '■t' - 1 r ^ Moc uiw V,..;- i.- r.v^' • .... ; . ; • . ^ ,vc‘l \o(ll rfo^.'ivs' |t 
 
 k 'd' it n.i.zi.’-* -j! * , '. . c . ; ^ •! ,/ u£ t*,; . no l| 
 
 j.:_ 1«J i;.'; \IC'Vl5 '■ i'ti XLi Ifn i£ ~ : dOO -• iliaUjXjB ■■ 
 
 . , ^ ’ ' 
 i rr : 'U.'j r.tr V , x,r. r tr;.i 'i' i.:y< . .. .'rcVi r 
 
 «( :, ; '_:tO) .: ■ fiJfiXjji t ' 
 
 
 cf u i ..X i ,n. i- - C . ::s{i • 
 
 . ‘ X;^ ',» 
 
 I' 
 
 — :j .t ; 
 
 
 ^ \ 1 ,. . S' . .tVk,,- . ■; i. I I z d -J'' -•-. . it>A' ri.jj,i^*.rf f 
 
 - ■'••■ ' ks- : I ' » -• - .« ;.-i •*• \l *i .biw Sfiu^^iiaJQU niSr ' 
 
 ■>"=' I 
 
 t ■■ i' iv. r,i*u'-' ?:/;'■ * r.o'lt, /f.ii.'i lo 
 
 : . C’. -iv -v.-j-' .ir^. 
 
 A 4 ^ 
 
 V j: ^ / f . X 00 ; .• >. WQ A ^ t ifc 
 
 1 ! w * . . 
 
 rt 
 
 0 "O fifeO*^ 
 
 .,^ 'io ]i^ 
 
 :,a -J i i: 
 
 ■•*• • f *'•■ £'• .. ' i/.u O. 
 
 X;^ ;^rI;U ;.?f .Ci 
 
 n f' 
 
 ^ c:c'.i; .•.•.".vcjeti Vi.' £>£(;x oi':: *; n I; ocoi£:i;-' Ins: . :..o .o li pit 
 
 h -' 
 
 r.Tiv yX.'i' .'ii' 
 
 n i r : 
 
 f>iiC ^ ly ?».( oit u ' . ‘■Is; ..;. *i'. <..c-Trl tdS 
 
 \ 
 
 ' &f V n.' V . iiSrtlvif: v£«Cun£je ^ c-^w 
 
 
 MfC 
 
 Ai f 1 
 
- 19 - 
 
 rather attractive glaze but not of the aventurine effect. The 
 color range does not seem to be uniform except that the glazes high 
 in iron oxide and low in boric acid and those low in iron oxide 
 and high in boric acid were lighter colored than the others. The 
 other colors were dark yellow, brown, black and purple. 
 
 i 
 
 The group containing O.I5 equivalents of alumina showed the 
 greatest tendency to produce aventurines. All of these glazes ex- 
 cept the ones high in iron oxide and low in boric acid and those 
 high in boric acid and low in iron oxide showed more or less aven- 
 turine spangles. These excep^tions produced yellow colored glazes 
 while the others produced darker colors. The glazes lowest in iron 
 oxide and lowest in boric acid showed the best aventurines, produc- 
 ing large patches of the true red and gold goldstone effects. In 
 this group the glazes highest in iron oxide and highest in boric 
 acid had a tendency to produce matt textures. 
 
 In all the groups the glazes highest in iron oxide and lowest 
 in boric acid and those highest in boric acid and lowest in iron 
 showed more of a tendency to craze than the others. 
 
 One peculiar effect noticed is that in each group, the glaze 
 with the highest iron oxide and highest boric acid content pro- 
 duced a bright brownish-purple colored glaze which had a good, 
 glossy finish and good texture. This color grew darker as the 
 alumina content increased. The glaze of this composition in the 
 O0I5 alumina group was the best colored and finished, being glossy 
 and smooth with no pinholing or crazing. It was uniform in color 
 and texture and was thick with very tiny, minute aventurine spangles I 
 which did not show up well except xinder the electric light. The 
 glaze developed well clear down to the edges of the piece. It dev- 
 
^ v;: f.; ;; 
 
 ^( 5 ! ^ '-'i :^; 
 
 ':<i i 'i ■ i. I Si i 
 
 . rx .. . r . .; ' - - t ^ t . 
 
 r ' i rusits jit:. 
 
 ' n . 
 
 t.;' ; . 
 
 . . ■ r 'i ;■ t (. i , 
 
 - ' • c vj; I L*»Y , 
 
 'i is <|I '■' • WOi D.*-..;!. fr 
 
 (-■ . , l '| . ■ s'^ I ' ■ V . , ’ i 
 
 ;ii o r.... r r V- Osii^a iv 
 
 t'lj c j v.>:i u *io£6o 
 
 ofci t . jlXo »o*i 1 fti 
 
 ' ICJ, - 
 
 ■ :, -'ir 'I 'tdj'i, •_• 
 
 ui't:lr^tp?Tvc. 5 ^. :.'r'j.v ttrfT' - 
 
 >1 /J \: •.■.*<■ .: . wi; * 
 
 .• ^ »<3 • -'cnc * J. . , r.. t> 
 
 . >Xrg§ - s'.f ill :i> i ; 
 
 ' , •■ji.-ifLi onxv.;;^ 
 
 . - j .- . «*■ 'c> ♦i^.iii. 
 
 i -eljiro 
 
 . -.‘OtVir . -J airij •\. xfei w:i 
 
 ■’ .it. : • •' ' c/ XiSv* uvTi L Ti .>•» ■'' t •r.*' j - . -i 
 
 * • J <-rr. . : v".^oij|a(|si tZ'C 
 
 — v~ •'-L t ..... , :*■' ■• ■. ■; : I ’ o '. xXi‘ cl 
 
 ■ '■ •: U;i :,i*i >:< . . • '.'i:. , i- &iircf Gx 
 
 ♦ - rj .- .ru-ij .1 •- S _ ‘i’c;a L-j-r'^ru. 
 
 jSkw ; 'j .' .'*j ; . ,• £1 Mjx .'j”'.,* i.'J. ?t :'.e--.!-jr: oc. . r:aC;- 
 
 -■•i- i v, ^ ‘ M V'lt rfj t» 
 
 t -- !».'• ^ ' I , , ,.. _ : irr«ji: 7 .:^ i bb^:rt 
 
 Pfi’lt <Lk ' ‘.Xii v"‘i^ 'i ‘i .<’'•• , *i‘ « <T t"’ .i-r^ *T'' (•• ^COXj 
 
 ' ■'•c sirfs'' 'rr, £ • . ^ .‘i t w:'.' i. 
 
 •r.ol<:o I't 
 
 '».' r- V 
 
 T > V - i : 4 Of? ifi’ f 
 
 .-.-J 
 
 (fi 
 
 -'• -S fjfli*:-' 
 
 % 
 
 ■ . > V V iJlv .oifi., 'X rr 
 
 'LiJ- 
 
 &iUI 
 
 
 ':X'i if otiio . V 
 
 "I'-’i.- . sty,.-., xf!W tircilrj o(;.G 
 
 
 •tiidw 
 
 c Vr-' . . 
 
 •« - • • 
 
 i” t :: t 
 
 V • '* iJCrTf? x,:©sl01' 
 
 trk «M 
 
 
- 20 - 
 
 eloped at cone 05 and makes a very pleasing glaze. 
 
 The heat distribution through the kiln was not uniform so the 
 
 heat treatment of the glazes varies and it is hard to draw conclu- i 
 
 ! 
 
 sions as a result. | 
 
 Some of the glazes were dipped too thick and others too thin. 
 Most of the glazes showed improper blending of materials, j 
 
 With these handicaps it is hard to draw any uniform conclusions 
 from the results. The heat treatment given the kiln seems to have 
 been poor and the cooling especially seems to have been too rapid 
 for proper development of aventurine glazes. 
 
 Conclusions. 
 
 1. 0.15 equivalents of alumina gives a better condition for 
 the development of aventurines than a lower content. 
 
 2. A low iron oxide together with a low boric acid content 
 in this glaze with highest alumina content produces the 
 best goldstone effects. 
 
 3. High iron oxide content with high boric acid in the high 
 alumina glaze tends to give matt textures. 
 
 4. High iron oxide with low boric acid and high boric acid 
 with low iron gives yellow glazes with crazing tendencies, 
 
 5. Increasing alumina content gives more easily fusible 
 glazes. 
 
 6. The best temperature to develop these aventurines is cone 
 1 or cone 2* 
 
 7. * A good bright, brownish purple glaze maturing at cone 05 
 is developed with 0.I5 alumina, 0.95 iron oxide and 2.00 
 
 boric acid in this base glaze. 
 
 S. The glaze blending and heat treatment must be accurate 
 carefuiiY aventurine. glazes. 
 

 
 
 *.• QOXll 
 ' :i 
 
 V* • 
 
 .:\.T.r ', UflV . i.if.ia- u il*. ,'L' 
 
 I' -• ... ., .• ,. 
 
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 ■ " «. i-r:. : , 
 
 •Mif." CC t1»» J?v , i 
 
 ^']f 
 
 
 
 -f C -iStiiin. t»A| •: :Uif 
 
 ^af n- *. . ;n->T eiJS* 
 
 » 
 
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 ■ 1 : •- ..r-L Ui^H ’.■ ;*' 
 
 
 ..101 p 6 vi 
 
 *. t . 
 
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 jfe- 
 
 
 >1 KW 
 
 -rii.:. ¥rtlJluil‘ 
 
 i- ia ■' ".i 
 
 ’» 
 
 * ?S»S. 
 
 ^ 1 »’u A lt L . 
 
 l»;i !m. '’ t 
 
 it’, i. i 
 
 r.'Zi r? :; 
 
 •■ f . j. . yc 
 
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 V.. . 
 
 , i' :.J.i < .'- iX. ; 
 
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 . ^ 
 
 ► ■ • ‘ w ‘K'IJL 4 *'■ 
 
 I* 
 
 — Lf. ^ . I •: •. i || .. 
 
 • ‘ ■■ “J.L :.■... ■.. iw 
 
 
 
 
 I 
 
 I 
 
 h 
 
 t 
 
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 V f ■ 
 
 / a ^ ' >J .■' "a -‘ 'J 
 
 ) -• 
 
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 '■4 ilcX.’kvc ■, • % I'jc * 
 
 ■ ,'Ii'^ ■^ ' . L 5 - *«0 JMH 
 
 1 
 
 -^.1 
 
 . f. f: '*r.' 
 
 I ... . 
 
 y.i; .-< <*(® . .. .. 8, _js 
 
 tl '7 
 
 ■ r. . .-, 
 
 ■ *' . » • •^■JV 'J, t, . J; 
 

 
 
 - 21 - 
 
 
 
 
 Cone 3 (11900 C) Burn 
 
 
 The 
 
 glazes 
 
 used in this series were the s^-me as those used for 
 
 the 
 
 first 
 
 burn 
 
 except that 0.05 moles of Alumina were left out of 
 
 the 
 
 fritt 
 
 and added to the glaze later as raw clay in an attempt 
 
 to 
 
 take advantage of the plasticity of the raw clay to aid in hold- 
 
 ing the fritt in suspension. 
 
 
 The 
 
 glazes 
 
 were burned to cone 3 glazed saggars as before | 
 
 and 
 
 the results 
 
 are tabulated below. j 
 
 
 
 
 RESULTS OF GLOST BURN - Cone 3. 
 
 Glaze 
 
 Cone 
 
 Description of glaze 
 
 1 
 
 
 2 
 
 Light brownish purple, large metallic separations J 
 
 
 
 
 glossy. 
 
 2 
 
 
 1 
 
 Light brownish purple, minute aventurinr crystals j 
 
 
 
 
 glossy. 
 
 3 
 
 
 1 
 
 N 
 
 k 
 
 
 2 
 
 Light red color, good aventurine separation, dull • 
 
 5 
 
 
 3 
 
 Brown to black color, red aventurine separations 
 
 
 
 
 on edges, dull. 
 
 6 
 
 
 1 
 
 P\irple color, minute aventurine crystals , glossy . 
 
 7 
 
 
 3 
 
 Golden color, heavy metallic separ actions, dull. 
 
 
 
 2 
 
 Purple to golden, heavy aventurine separations. 
 
 
 
 
 glossy. 
 
 9 
 
 
 3 
 
 Golden, heavy aventurine separations, dull. 
 
 10 
 
 
 3 
 
 Dirty golden color, good aventiirine separations^on 
 
 
 
 
 edges , dull . 
 
 11 
 
 
 4 
 
 Reddish gold color , entirely crystallized, dull , 
 
 
 
 
 overburned. 
 
 12 
 
 
 4 
 
 H 
 
 13 
 
 
 4 
 
 tl 
 
 : 14 
 
 
 4 
 
 It 
 
 1 15 
 
 
 3 
 
 Reddish-brown color, heavy aventurine separations. 
 
 
 
 
 dull. 
 
 - 16 
 
 
 3 
 
 Reddish-brown color , metallic separations ,dull . 
 
 17 
 
 
 3 
 
 " ,beautiful aventurine crystals 
 
 
 
 
 on edges , bright 
 
-nTV. 
 
 
 . ... i., r-'f ' 
 
 \\X , 
 
 ..•■»' r-\. 
 
 
 
 : V:? 
 
 nA 
 
 
 e£SC 
 
 J M ' -t . • 
 
 JScivi ftiki: 
 
 1 
 
 r i c. C . \ 
 
 
 fi- .' • '.P.- -;ai 
 
 ;;: 
 
 c: V t' 
 
 ' ; 
 
 ■ -r-'-T'" L. ■ 
 
 • I-. I ■ "'V.ii', fj i 
 
 
 :. ,*'y ;..'i v. 
 
 r*j '■ . 'i • >. o "■ 
 
 I .. 
 
 v: . ‘J. .. _ i 
 
 > 
 
 r: - 
 
 L.^,' > ‘ 
 
 r.;* 
 
 i J /■ :; 
 
 . . ' ■ I ■ ‘ ' 
 
 „ .J 
 
 ,. S ;> 'i ' 
 
 XTivy? - r<%V«-j Y 
 
 Jj i , l‘ i V "J •" ft . i *1 <• 1 1 1 * ■' • ■ !. ■ '.! 
 
 <**««>»• 
 
 ; 
 
 .i 
 
 . ■ i I 
 
Glaze 
 
 Cone 
 
 -22- 
 
 Description of elaze 
 
 Ig 
 
 4 
 
 Reddish golden color, entirely crystallized, dull , 
 
 19 
 
 4 
 
 over “burned. 
 
 20 
 
 4 
 
 Red to black color, heavy aventurine separations. 
 
 21 
 
 03 
 
 dull. 
 
 Light brownish purple color, no crystals , bright . 
 
 22 
 
 03 
 
 n 
 
 23 
 
 03 
 
 « 
 
 24 
 
 03 
 
 n 
 
 25 
 
 01 
 
 Black, few metallic separations, glossy. 
 
 26 
 
 3 
 
 Yellow, entirely crystallized, dull, overburned. 
 
 27 
 
 4 
 
 Muddy gray color , entirely crystallized, dull , over- 
 
 2g 
 
 4 
 
 b\irned. 
 
 n 
 
 29 
 
 1 
 
 Reddish gold color , beautiful crystals , dull . 
 
 30 
 
 3 
 
 Mottled gold and black , metallic separation,dull . 
 
 31 
 
 3 
 
 Reddish color , entirely crystallized, dull, over- 
 
 32 
 
 02 
 
 burned. 
 
 Muddy purple color , metallic separations, dull. 
 
 33 
 
 01 
 
 under-fired. 
 
 Purple to golden, heavy aventurine separations. 
 
 3^ 
 
 < 1 
 
 glossy. 
 
 n 
 
 35 
 
 2 
 
 Mottled red and gold, heavy metallic separation. 
 
 : 36 
 
 3 
 
 dull . 
 
 Dirty golden color , entirely crystallized, dull. 
 
 37 
 
 02 
 
 overburned. 
 
 Dark purple, golden aventurine crystals , glossy . 
 
 3S 
 
 3 
 
 Red to golden color, entirelycrystallized,dull. 
 
 39 
 
 3 
 
 overburned. 
 
 n 
 
 40 
 
 2 
 
 Red to black metallic and aventurine separations. 
 
 1 4l 
 
 03 
 
 glossy. 
 
 Dull reddish brown color, no crystals , semi-glossy , 
 
 42 
 
 02 
 
 Brownish purple, minute aventurine crystals, semi- : 
 
 
 1 
 
 glossy. 
 
 Golden brown color, heavy minute crystals , glossy , 
 
 44 
 
 1 
 
 Brownish purple color, few minute crystals , glossy . 
 
Glaze Cone 
 
 -23- 
 
 Description of glaze 
 
 ^5 
 
 1 
 
 Golden red color , beautiful aventurine crystals. 
 
 46 
 
 2 
 
 glossy. 
 
 Dark gray color , aventurine separations , dull , over- 
 
 1^7 
 
 02 
 
 burned. 
 
 Purple color, no crystals , glossy , under-fired. 
 
 4S 
 
 02 
 
 Purple gray, shows tendency to crystallize , glossy . 
 
 49 
 
 02 
 
 Purple, no crystals, glossy. 
 
 50 
 
 1 
 
 s 
 
 Reddish purple, good aventurine crystals, glossy . 
 
 51 
 
 3 
 
 Golden black color , metallic separations , dull. 
 
 52 
 
 01 
 
 overburned. 
 
 Grayish purple, few aventurine crystals , glossy . 
 
 53 
 
 01 
 
 Purple color, few aventurine separations , glossy . 
 
 5^ 
 
 1 
 
 Purple to golden red, heave avent\irine separations. 
 
 55 
 
 1 
 
 glossy. 
 
 Purple to dark red, beautiful aventurine separa- 
 
 56 
 
 2 
 
 tions, glossy. 
 
 Dull black, few aventurine separations , semi-glossy i 
 
 57 
 
 2 
 
 Dull black to golden, heavy aventurine separations! 
 
 5S 
 
 1 
 
 glossy . 
 
 Purple to golden, heavy aventurine separations. 
 
 59 
 
 1 
 
 glossy. 
 
 Purple to red-golden, heavy aventurine separations , 
 
 6o 
 
 2 
 
 glossy. 
 
 Red, mottled metallic separations , dull . 
 
 Discussion of Results of Cone 3 Burn. 
 
 The conclusions drawn from the first burn are pretty well demon-' 
 strated by this burn to be correct. Evidently cone 3 is too high a 
 
 temperature for 
 
 these glazes, as most of them are overbiirned. One 
 
 point 
 
 is brought 
 
 out quite strongly by this burn and that is the ef- 
 
 feet 
 
 of alumina 
 
 on the development of aventurine crystals. The 
 
 glazes in Group 
 
 I with only 0»05 moles of alumina are nearly all of 
 
 ! them 
 
 entirely crystallized, indicating that the glaze was quite 
 
 fluid 
 
 at cone 3 > 
 
 thus allowing heavy crystal separations. The 
 
 glaze 
 
 in Group III, on the other hand, have not crystallized so 
 
 f 
 
t 
 
 
 *> ■ .A- 
 
 
 f/b 
 
 1 4 fci i. , 
 
 _ _ i. ' ^ ' • . J. I, i jt' w' Jl! i j '.' '. 
 
 I t,. . .. ■ . ’.■•> •_ i T._ ■ 
 
 \ ^ ^ ^ t (' \ \ 1 t ' • 
 
 . V . If. f..' ■ 'i' ' 
 
 ► ■•':»- J - ri : : 1 , ■. 
 
 r * i '■ " *:•<" i x .- ’ 
 
 -f t. ’ ■ 
 
 ,-• I: ■ ' « 4 .'‘ t ■ / ■- t f 
 
 ‘ j . V r-r t 'i.. I 7oVii ,■ . 
 
 I : f 
 
 ivT* *• . 
 
 w 'll V iJ i, ' 
 
 . - cwt' 
 
 0 
 
 ; I I 
 
 i ■ . ( 
 
 
 ♦V ■ 
 
 . <, > ^ Oi J 
 
 - »'CO I 
 
 .V 
 
 j fmwA 
 
 'U H 
 
 I 
 
 ::el 
 
 
 r' Yi.;; ^ c.i* ii c : If.':;, v ’.i . ; ■.r'4.v 
 
 »- il'.- 1 iXr.i J 
 
 • -i'i iTU. ''.t fir* ; 
 
 >■ 
 
 . Wf!*i- ' - • 
 
 f* .. 
 
 .-Is c £*i : ; Lr / i.h \ - . i : 9^1:'^-. fac : 
 
 )', e?tT . :r- ;*!»/•; -.j -r'iVi; I .* .. -*tk.v -.'3 r... 
 
 I o i,l.v v.fi....-r*: rvniirti Z: "ic Cifllciv * .; s"il^ T 
 
 ! i i 'gffi-;* "iX-fri, • ^jr‘.Ls: i'. . : yi 
 
 * s. 
 
 li 
 
 I *;r. ; tl l£j<dVic w cn , ' 7srfJO e^Si’ 
 
 ' - r r, '- t;..: i r-s- -.. .■■•js -yafiXTyar 
 
 
 . < 
 
 'id '■■•i; , .-'■ 'I 
 
 , 1 ' 
 
 . r.;:-'ruXfii ;. cs': 
 
 ■ ■'* -1 
 
 I'O’iO .'i jj 
 
 o v;'- 
 
 ' D.TO'J JJ'J, 
 
 -. ' i: ii 
 
-24- 
 
 heavily, indicating that the glazes in this group were more vis- 
 cous at cone 3 and did not permit of such heavy crystallization. 
 The glazes of Group II are intermediate in this respect. 
 
 The tendency of the AlgO^ seems to be to give a deeper and 
 richer color to the glaze as the quantity increases as well as to 
 decrease the fluidity of the glaze. 
 
 The glazes with lowest iron and lowest boric acid content 
 seem to give the best aventurine crystals. 
 
 Conclusions from Cone 3 Burn. 
 
 1. Cone 3 is "fcoo high a temperature for these glazes, and 
 is likely the proper temperature at which to mature these 
 aventurine glazes, 
 
 2. Low boric acid and low iron give the best aventurine 
 crystals , 
 
 3. The other conclusions of the first burn are verified 
 
 Third Burn of First Part - Cone 1, 
 
 This series was the same as the second series but was burned 
 at cone 1 with careful heat regulation and with a little longer 
 time allowed for the maximum ten 5 )erature . 
 

 f X > 
 
 
 ’•..‘Jii; L-t v„.c^ 
 
 '■V •:;*■ 
 
 / i- ' > . r ■ 
 
 .. r *; V A 4 
 
 tXil- !- I 
 
 & iMo 
 
 . «•• e ' ^ 
 
 ‘^inV wi .'Ci.'.;. ■..c ■ 4 jLtj. li v’'*'’-' 
 
 
 yl^j er: 
 
 6-y : ;: <, • £' f 'iii 'iw ..Jt 
 
 . : f IT c • i . > ‘ *! 
 
 
 ■ \ 
 
 j t •■ 
 
 . t 
 
 r,:-'-3 ... ..o ,v Iftifoi'j 
 
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 ao5 i i' . i ' :■ X .> (• i; j I j ex(T 
 
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 . r'' ' ' ■ ' •■■■' 
 
 »4?-..i,L3 ..... . . ■•;£;•' t;<:4 nl , '/i4'*0 
 
 X X. .’iT C3 . X X :■: : .<4 V C^J^i.X 
 
 i 
 
 1i .T.'re) ■ ■ •■X -V*;, r.v'T.* cic. 4 
 
 , "-rfvia 
 
 *( 
 
 ’ 1 . : 'i. . il'i.J'rf o4»‘. i'J ;• » i"i» lv'> 
 
 ■ H X t ■■ 
 
 .tft 
 
 w 
 
 f ■ f 
 
 
 vXi i’i-.'O 
 
 t> w <? • '. * .-I 
 
 . I it* » # 
 
 *Xl4T 
 
 • 4 !^. 
 
 '■*' ‘.l9n^ I. arroc 
 
 « \ ' M ' w i* .. C- V . ^ . •• • i« /> «' 
 
 X^irftXXjl 
 
Glaze 
 
 Cone 
 
 1 
 
 01 
 
 2 
 
 01 
 
 3 
 
 02 
 
 4 
 
 1 
 
 5 
 
 1 
 
 6 
 
 1 
 
 7 
 
 1 
 
 S 
 
 2 
 
 9 
 
 2 
 
 10 
 
 2 
 
 11 
 
 2 
 
 12 
 
 2 
 
 13 
 
 2 
 
 i4 
 
 2 
 
 15 
 
 2 
 
 l6 
 
 01 
 
 17 
 
 01 
 
 IS 
 
 1 
 
 19 
 
 2 
 
 20 
 
 1 
 
 21 
 
 03 
 
 22 
 
 03 
 
 23 
 
 24 
 
 1 
 
 25 
 
 1 
 
 26 
 
 1 
 
 -25- 
 
 Results of Burn at Cone 1 (1150®C) 
 
 Description of glaze 
 Purple color, no crystals, glossy, crazed. j 
 
 ” , few minute crystals, glossy , crazed. | 
 
 ", " , dull, crazed. ! 
 
 l 
 
 I 
 
 Golden red, almost entirely crystallized, dull. 
 
 Reddish black, beautiful aventurine crystals, 
 glossy. 
 
 Brownish purple, heavy with minute golden crystali 
 glossy. 
 
 n 
 
 Golden, entirely crystallized, dull. 
 
 > f • 
 
 Red-golden, entirely crystallized, dull. 
 
 H n ft 
 
 n M « 
 
 * » • 
 
 Golden, entirely crystallized, dull. 
 
 n w n 
 
 » > » 
 
 Brownish-red, entirely crystallized, dull. 
 
 Brownish-black, few metallic separations, glossy. 
 
 Brown, few metallic separations, glossy. 
 
 Brown-red, patches of good aventurine crystals, 
 glossy. 
 
 Brown-red, entirely crystallized, dull. 
 
 Purple-black to golden, heavy with minute crystal^ 
 glossy. 
 
 Red, no crystals, not developed, dull. 
 
 Light golden, almost entirely crystallized, dull. 
 Gunmetal color, patches of good crystals, glossy. 
 Red-p\irple, no crystals, glossy. 
 

 
 — 26“* 
 
 Glaze 
 
 Cone 
 
 Desdription of glaze 
 
 27 
 
 1 
 
 Red-purple, no crystals, glossy. 
 
 2& 
 
 1 
 
 Gray -purple, minute aventurine crystals, glossy. 
 
 29 
 
 2 
 
 Red-golden, entirely crystallized, glossy. 
 
 I 
 
 30 
 
 1 
 
 Black, beautifully crystallized, glossy. j 
 
 31 
 
 1 
 
 1 
 
 Red-purple, no crystals, glossy, crazed. 
 
 32 
 
 1 
 
 n n n n 
 
 f » » • I 
 
 33 
 
 1 
 
 Red-purple, few minute crystals, glossy, crazed. 
 
 3‘^ 
 
 1 
 
 Red-purple to golden aventurine, glossy. 
 
 35 
 
 1 
 
 Black, metallic separations, glossy. 
 
 36 
 
 1 
 
 Red-purple, no crystals, crazed, glossy. 
 
 37 
 
 1 
 
 Dark purple, no crystals, crazed, glossy. 
 
 3S 
 
 1 
 
 Gray -purple, minute crystals, glossy. 
 
 39 
 
 2 
 
 Golden, entirely crystallized, dull. 
 
 4o 
 
 1 
 
 Black, beautifully crystallized, glossy. 
 
 41 
 
 03 
 
 Dull brown, no crystals, dull, underfired. 
 
 42 
 
 1 
 
 Brown-purple, no crystals, glossy, crazed. 
 
 
 1 
 
 Purple, minute crystals, glossy. 
 
 44 
 
 1 
 
 Gold-purple, many minute crystals, glossy. 
 
 ^5 
 
 1 
 
 Red beautiful aventurine crystals, glossy. 
 
 46 
 
 1 
 
 Purple, no crystals, crazed, glossy. 
 
 ; 47 
 
 1 
 
 n It n « 
 
 » » » • 1 
 
 4S 
 
 1 
 
 It n It n 
 
 > i i • 
 
 ’ 49 
 
 1 
 
 It II It It 
 
 » > » • 
 
 50 
 
 1 
 
 Red-brown, heavily crystallized, matt texture. 
 
 ' 51 
 
 1 
 
 Red, no crystals, glossy, crazed. 
 
 52 
 
 1 
 
 Mottled purple , no crystals, glossy. 
 
 53 
 
 1 
 
 Red-purple, no crystals, glossy, crazed* 
 

 JCS: 
 
 II 
 
 
 
 Ci 
 
 i 
 
 > - '. ■• 'xo a - , 
 
 ^ w - * . - • 
 
 - 
 
 
 : . \ fin 
 
 c iOAid 
 
 i 
 
 '‘I -:s 
 
 t , 
 
 
 
 r 
 
 >v'.x^ 
 
 W ^1! 
 
 1 
 
 •• ^ 
 t 
 
 £ 
 
 A ■ 
 
 i 
 
 S 
 
 
 
 
 , . 1 
 
 '■ 4 r f ' . . . •-, f.;i 
 
 JL 
 
 i 
 
 V 
 
 ..idffjk 
 
 
 J 
 
 t-C 
 
 
 
 
 t ^ 
 
 V . 
 
 '■ ' 1 i i? X' 'i .' n r :•. . 
 
 
 
 cc 
 
 
 1 
 
 
 
 4 Z\1‘. ^ . •, V t ' ' 
 
 -4 . 
 
 , 
 
 
 -•. -ii , „..• . 
 
 
 i 
 
 ' 
 
 >. 4 “ ■ i ' '_ 
 
 
 l‘ 
 
 h 
 
 ■t 
 
 
 
 
 \ ' 
 
 1 '. i'- . . 
 
 - * j_ . ^ ' *■ J. ' , 
 
 1 
 
 
 t ^ 4 « jT .■•. w ^ •; 'i 
 
 • 4'. - , . , uX'.( 
 
 CO 
 
 
 • s • •- 
 
 • 4 
 
 - ***y ^ ^ \ 
 
 •m 
 
 U‘ 
 
 * , ' ^ ‘ 1 • 
 
 - •.' '! 
 
 ; 
 
 • « 
 
 r I 
 
 . '^ ',. '.1 ■ ’ . ’ • 1 V 1 , A t 
 
 . 
 
 4 , i "; ■ f, 
 
 
 4i^ 
 
 oV*A 
 
 ;j 
 
 i " 
 
 I ^ 
 
 . •<»4 
 
 f 
 
 i I 
 
 't 
 
 t ^ 
 
 t 
 
 i : 
 
 r 
 
 1. >1- V, 
 
 t 
 
 V 
 
 t 
 
 
 I • 
 
 
 t 
 
 ’< " 
 
 ( 
 
 M 
 
 *' It 
 
 I 
 
 "i I » ' i •• ' ‘ 
 
 . '• LfC- 
 
 -•. i. 
 
 
- 27 - 
 
 Glaze 
 
 Cone 
 
 Description of glaze 
 
 Red-purple, no crystals, glossy, crazed, 
 
 ” ,few minute crystals , glossy, crazed. 
 
 54 
 
 55 
 
 56 
 
 57 
 
 5S 
 
 59 
 
 60 
 
 1 Purple-red, no crystals, glossy, crazed 
 1 Red-p\irple, " , ", " 
 
 1 Purple, no crystals, glossy, crazed. 
 
 1 Red, no crystals, glossy, crazed. 
 
 1 
 
 1 
 
 1 
 
 n 
 
 > 
 
 n 
 
 n 
 
 n 
 
 Discussion of Results of Third Burn (at Cone 1.) 
 
 As in the previous burns, the higher alumina content gives a 
 more viscous glaze and retards crystallization to a very marked 
 degree. The temperature of this burn is evidently the proper mat- 
 uring temperature for these glazes as most of them turned out glossy 
 and smooth. 
 
 The low iron and low boric acid glazes give the best aventur- 
 ine crystals, and the most beautiful glazes. Increased iron con- 
 tent seems to give the glaze more of a red color than the lower 
 iron content , 
 
 When these glases do not develop any aventurine effect they 
 nevertheless produce beautiful mottled purple colored glazes. 
 
 Conclusions from Third Burn (at cone 1) 
 
 The conclusions drawn from this burn coincide with the conclu- 
 sions of the two previous burns. 
 
 General C o nclusions on Effect of Heat Treatment an d 
 Variations in the content of Aliimlna, iron and boric acid . 
 
 The general conclusions drawn from the foregoing work are; 
 
 1. Aventurine glazes with these variable compositions mature 
 
w 
 
 
 t'V=^ ^0 ^ • . .' '^X i - 1 
 
 j, “ a {. 
 
 
 '¥ 
 
 C 
 
 M ’ »* 
 
 4 « . X 
 
 ' . -fctfK 
 
 X 
 
 : ' 
 
 
 V. ' . 1x1 *i 
 
 X '' ■*". 
 
 ) 
 
 t 
 
 •f* , ) 
 
 v<.; 1 
 
 . ■’ i;r,'iT To b-- ^ ; 
 
 . V I.'..;; •'ll 43 
 
 ! 
 
 1! 
 
 *: 
 
 •■ ■■ ^ ■ f w . 1- i «iA 
 
 1 
 
 i 
 
 - r oj; .;■ f . 1 V w L' - 
 
 •1 c V ’a f '• 
 
 (WOOctV 
 
 |l 
 
 » J 
 
 Vl^W»t>iV0 CIS L'l- '.< 
 
 ^C- 
 
 w! cdT * 
 
 i 
 
 ‘>‘u-fc yo sS'Oia c,*. QesbXt 
 
 ■, .bjfJ -wl 
 
 
 4 «oo«» ixijj: 
 
 i.' 
 
 ->i - v; i*v>-n ? to.. z »,w.^ .■ rfT. j» 
 
 /<■ . ^9CM Ti: ,> ^ ^j^j. ^,. 
 
 ; ',. 
 
 - 'iv • •- • :■■ J :>e8 hlBit. 
 
 ‘ . »>C 
 
 jj ^r*'* '-- ‘,ic> T : V ; •< . i:,n bb worn '. --^^j 
 
 « ■■■ • '’'ivl.-c ‘A *•■"■’ '1'. i. i! :'.^T - ; •. «.- ' 
 
 * j 
 
 ( <■ ; ut-O >'•<.•) ijiax’S in ;. .kC i": ’^T'C I ■■-ti /'•;'' ., ’• .• 
 
 - 'lor . t •• J ■ ■■ ■ •' •: a . •' i':H:Xa4icc VtfT c.’i’ !• 
 
 avolv—K. owj "tc u , 
 
 > ' # 
 
 » . i .0 . ^ 
 
 . out,,.,,' ^\inCu.'X^‘i t 
 
-2S- 
 
 at cone 1 • 
 
 2. Increasing alumina content retards crystallization, 
 
 3 . Best aventurine glazes were obtained with low iron and low 
 borid acid content. 
 
 4 . Least crazing was found in areas of maximum crystalliza- 
 tion. 
 
 5 . In areas where no crystallization takes place, beautiful 
 mottled, glossy glazes are produced with a rsd“p\irple color 
 
 6. To produce the best results, the glaze materials must be 
 entirely fritted together before being applied to the piece 
 
 7. Careful blending and careful firing and cooling must be 
 regarded for the proper development of aventurine glazes, 
 
 S. The best aventurine glaze produced has the following com- 
 position; 
 
 (0.15 AI2O3) 
 
 1.00 Na20 (1.25 B2O3 I 7.0 Si02 
 
 (0.75 
 
 Part II. 
 
 In the second part of the investigation an attempt was made to 
 determine the effects of variations in the R 0 group on the devel- 
 opment of aventurine glazes and their maturing temperature. This 
 was accomplished as outlined in the Method of Investigation. The 
 tri-axial diagrams showing the R 0 composition of each glaze are 
 given in diagrams V,VI ,VII ,VIII , and IX. 
 
 The method of preparing the glazes and of blending is the same 
 as given for Part I, Series I and the firing was carried out to 
 

 t 
 
 ( 
 
 ( 
 
 . 1.1 
 
 ,^•c •• ■ ■ • . . • ; -1 . r \ r .. .. . 7f i'r;l 'j 
 
 .... . ; ■ ' ■ . . ; *■' I 'V-jCnz. >i 
 
 i • f.3: . V''..'! T' f A X/t‘ «JW» ■■; 
 
 • . • o . '■ V ■; 1'e rtt ii-Ir 
 
-29- 
 
 cone 1» 
 
 The glaze formula with the R 0 variations used in this work 
 is as follows: - 
 
 0.0 to 1.00 Na 0 
 0.0 to 1.00 K26 
 0.0 to 1.00 CaO 
 0.0 to 1.00 PbO 
 
 ) 0.15 Al-0,) 
 ) 1,25 B 2 ^ 0 i ) 
 
 0-75 
 
 Fc20^) 
 
 7.0 SiOg 
 
 The glaze compositions, batch weights, and RO components of 
 each glaze are given in the following tables. 
 
 Glaze composition and Batch Weights 
 
 Glaze 1: 
 
 0,70 
 
 0-75 
 
 Glaze 362 
 
 1.00 
 
 0.15 
 
 6.70 
 
 1.25 
 
 0,75 
 
 Glaze 51 : 
 
 1.00 
 
 0.15 
 
 6.70 
 
 1.25 
 
 0,75 
 
 Glaze 56: 
 
 1.00 
 
 0.15 
 
 6.70 
 
 1.25 
 
 0.75 
 
 0.625 Borax — - — - — 1906.O — 
 
 0.375 Soda Ash-—- 31S.4 
 
 0.15 Clay- 309.6 
 
 Flint— — 3216. Oir 
 
 Fe203‘ 
 
 KpOOt- 
 
 Clay^-" 
 
 Flint- 
 
 Comb • 
 Weight . 
 — -126,00 
 
 — 23.25 
 
 — 3^.20 
 
 — 402.00 
 
 120 .00 
 
 Whiting" 
 
 Clay 
 
 Flint— 
 
 ®2®3 
 
 Fe203 — 
 
 6712.6 
 
 1104.0 
 309.6 
 
 3216.0 
 
 700.0 
 
 960.0 
 62^9.6 
 
 70^5 
 
 94.00 
 
 34.20 
 
 402.00 
 
 67.50 
 
 120.00 
 
 737.70 
 
 600.0 56.00 
 
 309.6 — - 3^.20 
 
 3216.0 — 402.00 
 
 700.0 — — S7.5O 
 
 960.0 — — 120.00 
 
 5935. 6 699.70 
 
 mte lead- 
 
 Clay — 
 
 Flint—" 
 B2O3 — 
 
 *3“^’ — 
 
 Fe gU- 
 
 1035.0 
 309.6 
 
 3216.0 
 
 700.0 
 
 960.0 
 
 223.00 
 34.20 
 
 402.00 
 
 67.50 
 
 120.00 
 
 msTfu 
 
 I 
 
f 
 
 r\ 
 
I? 
 
 I 
 
 I 
 
 \ 
 
 
> 
 
-30- 
 
 RO Component 3 of Part II 
 
 Glaze RO Components . 
 
 1 1,00 Na20 
 
 
 
 
 2 o.S 
 
 Na20, 0.2 K20 
 
 
 
 
 ^ 0.6 
 
 Na20, 0.2 CaO 
 
 
 
 
 4 0.6 
 
 Na20, 0.2 PbO 
 
 
 
 
 5 0.6 
 
 Na20, 0.4 K20 
 
 
 
 
 5 0.6 
 
 Na20, 0.2 K20 
 
 , 0.2 CaO 
 
 
 
 7 0.6 
 
 Na20, 0.2 K20 
 
 , 0,2 PbO 
 
 
 
 g — 0.6 
 
 Na20, 0.4 CaO 
 
 
 
 
 ^ 0,6 
 
 Na20, 0.2 CaO 
 
 , 0.2 PbO 
 
 
 
 10 — — — 0.6 
 
 Na20, 0.4 PbO 
 
 
 
 
 11 0.4 
 
 Na 20 , 0.6 K 20 
 
 
 
 
 12 — — 0.4 
 
 Na20, 0.4 K20 
 
 , 0,2 CaO 
 
 
 
 1 ^ — 0.4 
 
 Na20, 0.4 K20 
 
 , 0.2 PbO 
 
 
 
 l4 0.4 
 
 Na20, 0.2 K20 
 
 , 0,4 CaO 
 
 
 
 15 0.4 
 
 Na20, 0.2 K20 
 
 , 0.2 CaO, 
 
 0,2 
 
 PbO 
 
 16 0.4 
 
 Na20, 0.2 K20 
 
 , 0.4 PbO 
 
 
 
 17 — 0.4 
 
 Na20, 0.6 CaO 
 
 
 
 
 IS 0.4 
 
 Na20, 0.4 CaO 
 
 , 0.2 PbO 
 
 
 
 19 0.4 
 
 Na20, 0.2 CaO 
 
 , 0,4 PbO 
 
 
 
 20 0.4 
 
 Na20, 0.6 PbO 
 
 
 
 
 21 — 0.2 
 
 Na20, 0.6 K20 
 
 
 
 
 22 0.2 
 
 Na20, 0.6 K20, 
 
 0.2 CaO 
 
 
 
 23 0.2 
 
 Na20, 0.6 K20 
 
 , 0.2 PbO 
 
 
 
 24 — 0.2 
 
 Na20, 0.4 K 20 
 
 , 0.4 C aO 
 
 
 
 25 — 0.2 
 
 Na 20 , 0,4 K 20 
 
 , 0,2 CaO, 
 
 0.2 
 
 PbO 
 
 26 0.2 
 
 Na20, 0.4 K20 
 
 , 0.4 PbO 
 
 
 
 27 0.2 
 
 Na 20 , 0.2 K 20 
 
 , 0.6 CaO 
 
 
 
 28 0.2 
 
 Na20, 0.2 K20 
 
 , 0.4 CaO, 
 
 0.2 
 
 PbO 
 
 29 0.2 
 
 Na20, 0.2 K20 
 
 , 0.2 CaO , 
 
 0.4 PbO 
 
 30 — — — 0.2 
 
 Na20, 0.2 K20 
 
 , 0.6 PbO 
 
 
 
 31 0.2 
 
 Na20, 0.6 CaO 
 
 
 
 
 32 0.2 
 
 Na20, 0.6 CaO 
 
 , 0.2 PbO 
 
 
 
 
 Na20, 0.4 CaO 
 
 , 0.4 PbO 
 
 
 
 
 Na20, 0,2 CaO 
 
 , 0.6 PbO 
 
 
 
 35 0.2 
 
 Na20, 0.6 PbO 
 
 
 
 
 36 1,0 
 
 K20 
 
 
 
 
 37 0.6 
 
 K20, 0,2 CaO 
 
 
 
 
 3 S ... 0.6 
 
 K20, 0,2 PbO 
 
 
 
 
 79 0.6 
 
 K20, 0.4 CaO 
 
 
 
 
 4o — . 0.6 
 
 K20, 0,2 CaO, 
 
 0.2 PbO 
 
 
 
 4 i — — — 0.6 
 
 K20, 0.4 PbO 
 
 
 
 
 42 0.4 
 
 K20, 0.6 CaO 
 
 
 
 
 43 ... 0.4 
 
 K20, 0,4 CaO, 
 
 0,2 PbO 
 
 
 
 44 — 0.4 
 
 K20, 0,2 CaO, 
 
 0.4 PbO 
 
 
 
 45 0.4 
 
 K20, 0.6 PbO 
 
 
 
 
 48 0.2 
 
 K20, 0.6 CaO 
 
 
 
 
 47 ... — .. 0.2 
 
 K20, 0,6 CaO, 
 
 0.2 PbO 
 
 
 
 4 g 0.2 
 
 K20, 0,4 CaO, 
 
 0.4 PbO 
 
 
 
 49 0.2 
 
 K20, 0.2 CaO, 
 
 0,6 PbO 
 
 
 
 50 — 0.2 
 
 K20, 0,6 PbO 
 
 
 
 
4 
 

 
 - ■'' ( 
 
 - 31 - 1 
 
 Glaze 
 
 RO Components 
 
 51 — 
 
 1.0 CaO 
 
 52 
 
 O.S CaO, 0.2 PbO ] 
 
 p 
 
 ?3 
 
 0.6 8 aO, 0.4 PbO j 
 
 p 
 
 
 
 0,4 CaO, 0.6 Pb0 1 
 
 55 
 
 0.2 CaO, O.S PbO ! 
 
 56 — 
 
 1 .0 PbO 1 
 
 II 
 
 
 RESULTS 
 
 OF GLOST BURN— VARIATIONS IN RO MEMBERS - Cone 1. j 
 
 Glaze 
 
 Cone 
 
 Description of ^laze 
 
 1 
 
 1 
 
 Purple red with good aventurine crystals, glossy. 
 
 2 
 
 1 
 
 Black, good aventurine crystals, glossy. i 
 
 3 
 
 1 
 
 Deep brown, good crystallization, matt textiors. 
 
 4 
 
 1 
 
 Purple-brown, no crystals, glossy. 
 
 5 
 
 1 
 
 Reddish-black, good crystallization, matt texture! 
 
 6 
 
 1 
 
 Black, metallic separations, glossy. 
 
 7 
 
 1 
 
 Red-purple , no crystals, glossy. 
 
 g 
 
 1 
 
 Purple, no crystals, semi-matt texture. 
 
 9 
 
 1 
 
 Brown-purple, no crystals, glossy. 
 
 10 
 
 1 
 
 n 
 
 11 
 
 2 
 
 Black, metallic and aventurine separations , glossy 1 
 
 12 
 
 1 
 
 Red-brown, minute aventurine crystals, glossy. 
 
 13 
 
 1 
 
 Brown-purple, no crystals, glossy. 
 
 14 
 
 1 
 
 Purple, no ccystals, glossy. 
 
 15 
 
 1 
 
 Red, no crystals, glossy. 
 
 i 16 
 
 1 
 
 Red, no crystals, glossy. 
 
 17 
 
 1 
 
 Red-purple, no crystals, glossy. 
 
 IS 
 
 1 
 
 
 19 
 
 1 
 
 Red-purple, few minute crystals, glossy. 
 
 20 
 
 1 
 
 Red, no crystals, glossy. 
 
 21 
 
 1 
 
 Red-gold, good aventurine, semi-matt. 
 
 i 
 
'■I ■■t 
 
 
 
 
 I 
 
 / 
 
 1 
 
 j: 
 
 V 
 
 t 
 
 
 r 
 
 t. 
 
 
 i 
 
-32- 
 
 Glaze 
 
 22 
 
 23 
 
 24 
 
 25 
 
 26 
 
 27 
 
 2S 
 
 29 
 
 30 
 
 31 
 
 32 
 
 33 
 3^ 
 
 35 
 
 36 
 
 37 
 3S 
 
 39 
 
 40 
 
 41 
 
 42 
 
 ^3 
 
 44 
 
 ^5 
 
 46 
 
 47 
 
 45 
 
 Cone 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 01 
 
 2 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 Description of glaze 
 Deep purple, good aventurine, glossy. 
 Red-purple, no crystals, glossy. 
 
 Deep brown-purple , few crystals, glossy. 
 
 Deep gray-purple, few crystals, glossy. 
 Red“purple, no crystals, glossy. 
 
 Deep gray-purple, very minute crystals, glossy. 
 
 " , no crystals, glossy, 
 
 n tt ti 
 
 » f * 
 
 Red-purple, no crystals, glossy. 
 
 Dull black, very few crystals, dull. 
 
 Deep purple, very minute crystals, glossy. 
 
 « « It 
 
 » » • 
 
 Red-purple, no crystals, glossy. 
 
 Red-purple, no crystals, glossy. 
 
 Deep brown, metallic and aventurine separations 
 glossy . 
 
 Gold-jpnrple , very minute crystals, glossy. 
 Red-purple, no crystals, glossy. 
 
 Red-brown, no crystals, matt texture. 
 
 Black, no crystals, matt-texture. 
 
 Deep brown, no crystals, semi-matt texture. 
 
 Deep brown-purple, no crystals. 
 
 Red-brown, no crystals, glossy. 
 
 n n n 
 
 > » • 
 
 Red, no crystals, glossy. 
 
 Black-purple, no crystals, semi-glossy. 
 
 n « « 
 
 » t • 
 
 » 
 
. , , ,f '• ; tytr' • • , . ■. ,: ■ 
 
 V 
 
 /r 
 
 
 I 
 
 1 
 
 
 t 
 
 
 n 
 
 ')i 
 
 \ 
 
 ? 
 
 ri 
 
-33- 
 
 Glaze 
 
 Cone 
 
 Description of glaze 
 
 ^9 
 
 1 
 
 Black-purple, no crystals, semi-glossy. 
 
 50 
 
 1 
 
 Deep brown, no crystals, semi-glossy. 
 
 51 
 
 2 : 
 
 Black, no crystals, dull, under-fired. 
 
 52 
 
 2 
 
 Brown, " » ^ * 
 
 53 
 
 1 
 
 Red-brown, no crystals, dull , under -fired. 
 
 5|f 
 
 1 
 
 « « n tt . 
 
 » » » • 
 
 55 
 
 1 
 
 Red, no crystals, matt texture. 
 
 56 
 
 1 
 
 H ^ If It ^ 
 
 ■.» » > * 
 
 DisGUSBion of Results of Gloat Burn with Variable R 0 
 Soda seems to be the member of the R 0 group which most assists 
 crystallization. The glazes centered around the soda vertex of the 
 pyramid all showed crystallization to a marked extent but the amount 
 of crystallization diminished toward the other vertices. Potash 
 was the next agent most conducive to crystallization, which is in- 
 dicated by the formation of crystals in the trials all the way from 
 the soda to the potash vertex. Lime and lead both seem to hinder 
 the formation of crystals, probably because of the high viscocity 
 of the glazes containing these R 0 members. 
 
 Lead and lime both made the glazes more refractory so that 
 their maturing temperature is well above cone 1. Lime made the 
 most refractory glaze of all. 
 
 The only effects noticed on the color was that lead gave the 
 glazes a reddish-purple tinge which became more pronounced as the 
 lead vertex was approached, becoming quite red-purple at the lead 
 vertex , 
 
- 34 - 
 
 Conclusions on the Effect of Soda, Lime, Potash and 
 Lead on Aventurine Glazes, 
 
 From the above work, the follov/ing conclusions are deduced: 
 
 1, Soda aids the production of aventurine glazes more than 
 any of the other R 0 member® employed, 
 
 2, Lime gives the most refractory glaze of all R 0 members 
 employed, 
 
 3, Potash is the second best agent in the production of Aven- 
 turine glazes and lead is next, 
 
 4, The color of the glazes is little effected by the R 0 
 members employed except by lead which gives a decided red- 
 purple color to the glazes, 
 
 5» The influence of soda in the production of aventurine 
 glazes in combination with other R 0 oxides is very strong, 
 
 A little soda in the glaze makes a vast difference in the 
 fusibility and the tendency to form crystals. 
 
 XI 
 
 General Conclusions, 
 
 The general conclusions drawn from this study of aventurine 
 glazes are;- 
 
 lo For the production of aventurine glazes a slowly increas- 
 ing and steadily oxidizing fire is necessary. The rate of 
 cooling must be slow for the proper production of aventurine 
 crystals . 
 
 2, An increase in SiOg requires an increase FegO^ to produce 
 aventurine glazes, (Schurect) 
 
 3* An increase in the iron contentincreases the size and 
 

 
 
 t t.A- »'i-.l'OJ> %o 
 
 * L:. .J ■ • A 4 t V.' tH L i 
 
 "• ‘ '>. vilTCO -^.CL ''i e\-i^ ^ -r: w •-..■■ 
 
 ;. l; jc i a tt it^,. ' 
 
 0 a 'itrivo t;'..'. 
 
 .Li.-, iv Il-Jsl ' ’ C €»^ 1 
 
 - ' V 
 
 ■•' . 1 -''u;: ■ 
 
 
 t ^'j 2 c©" -'o f. 
 
 r^A‘’ 
 
 - . L- f 1 : i, ft 
 
 V' 
 
 PV 
 
 ci V is: 
 
 V. u S 
 
 »V 1 
 
 'tv 
 
 \ii' 
 
 
 '^'i.;Cv J*;-; U»'J .*4 'S - 1 ^ iP 
 
 nvi-** '^y:r V ■■■^ -.r.'-i :.i " R 'i'-f!:' rf*t^ ,i :J :f^!ifi.nvco .'^ i .'i?^-A'; 
 
 r'.r'.5r'3s‘f. 1 : rd.«V ; «• 5 \ 4tf, v:i .i •-•]::';MX 
 
 • V 1 
 
 . *. ■ K •■ I" :1p'i C.J V-f;2rl'^' ' V .' i £,H L c: A 
 
 'A>;: ■ 
 
 V 
 
 v ♦ 
 
 I v'; 
 
 \ 
 
 ) V» 
 
 
 
number of crystals and also the refractoriness of the gla^^e. 
 
 (Schurecht) 
 
 4. An increase of Na^O increases crystallization. Bromberg 
 incorporated this conclusion in his v/oric. (See page 7 of 
 this thesis). The conclusion was verified in my own worJic on 
 variations in the RO components. 
 
 3 . Aventurine glazes may be formed in the presence of .2 mole of 
 Al^O^. (Bromberg, see page 7 of this thesis) 
 
 6 . Aventurine crystals may be formed in the presence of CaO even 
 v>rhen there is as much as .4 mole present . (Bromberg, see page 7 
 of this thesis) 
 
 7. Decreasing the lead increases crystallization and decreases‘ the 
 gloss. (Bromberg, see page 7 of this thesis) iviy work on vari- 
 ations in the RO members verified his statement, 
 
 8 . Aventurine glazes are notrestricted to any pa-rticular molecular 
 or oxygen ratio, but come within the limits of good glazes. 
 (Bromberg, see page 7 of this thesis) 
 
 9 . A low iron oxide content (0.73 moles) together v/ith a low 
 boric acid content ( 1.23 naoles.) with high alumina (Q.I 3 moles) 
 and silica ( 7*00 moles) content produces the best goldstone 
 effects. This is my own observation and agrees with the obser- 
 vation of Schurecht. 
 
 10. Crazing occurs least in the areas of best crystallization. 
 
 This is contrary to the behavior of most crystalline glazes 
 but seems consistently true with aventurine s, 
 
 1 1 . From the observations of Bromberg and from the conclusions 
 
 of my own work on the variations in the RO contents, the order 
 of beneficial effect upon crystallization of the RO members 
 studied is as follows: 1 . soda. 2 . Potash, 3 , Lead, 4 , Lime, 
 

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- 36 - 
 
 In concluding this thesis 1 wish to express my thanks to 
 Professor C. W. Parmelee of the Ceramic hngineeriQgdepartment of 
 the University of Illinois f orchis aid^in directing my* work and 
 his assistance in tne collection of material, I further wish to 
 acknowlege my indebtedness to IJethan Bromberg and H. G, Schorecht 
 for the valuable information they have produced in their wrrx on 
 the subject of aventurine glazes, I also wish to thanx the Ceramic 
 Engineering students of the class of 1^22 for the information 
 they have given to me through their study of aventurine glazes 
 and the report of their work which I was allowed to summarize.