Y?/-\mm /if-, . /' ■»»i: ■>^;^ve?^ v.v ^jc^v/- i^i^fe^ I'i^Av'*, ^ V*. *v'-v'r ^"^r^ pa^ 1^^*^ W^^^f^ >v r%r -^^^ '-^ :^''M'' UNIVERSITY OF ILLINOIS LIBRARY '•, Class Book Volume ^Xfrd :^rW, V-.-^ ' ^ - v4->' ^•f^^^.. 'yUrn: 1. r ^lfr^« The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN J UNIVERSITY OF ILLINOIS BULLETIN Vol. V. AUGUST, 17, 1908 No. 39c [Entered February 14, 1902, at Urbana, Illinois, as second-class matter under Act of Congress of July 16th, 1894. BULLETIN No. 9. DEPARTMENT OF CERAMICS C. W. ROLFE, Director A CHEAP ENAMEL FOR STONEWARE By R. T. STULL THE VISCOSITY OF CLAY SLIPS By A. V. BLEININGER NOTE ON SOME FUSION CURVES By A. V. BLEININGER J 907- J 908 PUBLISHED FORTNIGHTLY By THE UNIVERSITY A CHEAP ENAMEL FOR STONEWARE. BY R. T. Stull, Urbaua, 111. The object of this work was to investioate some of the possibilities of producing- a cheap enamel, primarilY for the improvement of the l)etter grades of stoneware, and secondly, cheai:> enamels for other j^urposes at temperatures lower than those recjuired for the stoneware industry. The main object sought for was an enamel which would be whiter and better than the commercial stoneware glaze; something on the order of a tin enamel in appearance, though much cheaper. Xo special field was i)lotted for investigation. The method first adopted for carrjing out the work was to make up a series of glazes, then select the most promising one, after firing, for the upper member of the next series, and continuing thus. The method of preparing and api)lyiug each glaze in this work Avas the same, so as to obtain an accurate com- parison of results in so far as mechanical and physical application was concerned. The batch weight of each glaze was calculated from its respective formula, weighed sep- arately, (500 gm.l, ground wet for two hours in a small porcelain ball mill, passed through a 100 mesh sieve, placed in a Mason jar, allowed to settle and the water decanted. Sufficient water was then added in order to ''set'' the glaze at 1.5 B. »& L. hydrometer (equal to about 48 to 52 Beaume). Each glaze was then ready for dipping. Trials were made from ready prepared stoneware clay from Monmouth, 111. A test showed that the clay when made into slip form readily passed a 60 mesh screen but left quite a residue of dark colored granular particles on the 100 mesh screen. L ^ ■iMesf *'™*?™ T^ gv' L. ^,n^ (MR** 5*- .- > MM** NMM ^ A CHEAP ENAMEL FOR STONEWARE. The trial pieces were made in the form of small "milk" crocks 3'' across the top and li/o'' high. These were made in plaster molds on a jigger and fin- ished outside on a "potter's chum." The trials ^^ ere dipped in the bone dry condition, (Mich piece being immersed in tlie ghize al)out 21/0 sec- onds. Tlie dipped pieces were then placed on a pot- ter's Avheel, the glaze turned off from the rim and shoulder and the pieces nested in "fives" for setting in saggers. In order to determine the relative fusibility of the glazes, cones were made from each mixture and the bending points or softening temperatures determined by Seger cones and the Le Chatelier pyrometer. All the glazes in this work were fired in the down-draft open fire kiln of the ceramic department at the University of Illinois. Series I was fired to cone 6 in 12 hours, coke being the fuel used. For the starting point of this work, a glaze having the following formula* was selected : Trial pieces nested in "Fives" ready for the Sagger. No. I, Series I • 3 K.0 .4 CaO .3 BaO • 4 ALO., 3-75 SiO. This formula produces a clear bright glaze having a range of temperature from cone 4 to cone 8, within which it is a good glaze. *Sprechsaal ; 1905, No. 42. A CHEAP ENAMEL FOR STONEWARE. u o •suajjog 3ZEIO qoiqAi JE 3jnjKJ3(JUI3X o o o o_ 0° O O\00 lO " CH „ „ ►-. 1;^ en '53 i EI3JOSO 3up!qM jEdspidj auiMApuEjg CI ^(00 in to fe c5 O PJ Tl-VOOO O M '-' q o \n in ui ir> m IT) t^ m ro 1-1 o\ t^ re ro fO fO 0< OJ q < Tf Tft Tt -5}- Tt o O ■^00 01 \o CO 0) >-i '- O o O 0\0 0)00 TfO Tt ■* in io\0 t^ o to CO ro CO CO CO <^ O 'i o| CO Tt 0\ W W 1-, HH W 6 6 6 6 6 6 10 A CHEAP ENAMEL FOR STONEWARE. The trials, and cones made from the glazes for the fusibility test, were set in the kiln in the same manner as in the previous burns. Before a dull red heat was reached, all the cones made from those glazes containing colemanite crumbled to a fine powder on the placque. No. 9A, contain- ing no colemanite, remained standing. Powdered colema- nite dehydrates at a very low heat, swelling to nearly twice its original volume without softening, which accounts for the "falling to ]3owder'' of the cones made from those glazes in which colemanite was present. The first intention was to fire the trials to cone 6. From the behavior of the cones it was assumed that the colemanite glazes would crumble from the trials, hence the kiln was finished at cone 8 in order to mature No. 9A. Appearance of the Trials. No. 9A softened at 1250°C the same as in the previous burn, going down with cone 6. It was impossible to deter- mine the softening points of the other members of this series since their cones crumbled to powder in the early stage of the burning. No. 9A matured nicely, is a little whiter than in the previous burn. Nos. 10, 11, 12, 13 and 11 crumbled off from the out- sides of the crocks leaving them bare, and fell to the bottom on the insides, fusing in thick layers. No accurate conclu- sions could be drawn from these except -that they were much more fusible than No. 9 A and overfired. This is as far as the work has been carried. The next step will be to make a series in which the colemanite has been dehydrated after the same formulae as those in series IV. According to the composition and low temperature of fusion of colemanite, it is undoubtedly a valuable flux for the introduction of BoOg in an insoluble form. If it can be had in a reasonable state of purity in suflftcient quanti- ties, and at a moderate price, a large portion of the trouble A CHEAP ENAMEL FOR STONEWARE. "> sa S CT» O) O) 3avy*)llK/30 933^030 12 A CHEAP ENAMEL FOR STONEWARE. and expense of fritting can be eliminated. It will also be valuable in simplifying the leadless glaze problem, as well as a valuable Hux for hardening terra cotta slips for low fire work. DISCUSSION. Mr. Purdy : I will ask Mr. Stull two questions. One is as to the calcium phosphate. We known that increased whiteness and opacity of the glaze can be secured by use of bone ash, but can you use it to any great extent without having crawling? Mr. HtuU: I have not experimented extensively in using bone ash for a glaze ingredient, but here used .4 CaO as bone ash and there was no evidence of crawling. Whether more could be used, I do not know. It materially increases the temperature necessary to mature it. Mr. Furdjj : Bone ash, according to my experience, is a very dangerous substance to use in a glaze of that kind. Another question I will ask, in harmony with Prof. Binns' paper; does BoO.-j tend to increase the opacity of the glaze? Are vou getting a whiter glaze with increased content of B2O3? Mr. Stnll : I believe it depends on the composition of the glaze whether it imparts whiteness or not. In itself, I do not believe it does. But colemanite is borate of lime, practically insoluble when cold, though it fuses by itself at a low heat, and the theory is advanced that whiteness can be obtained by incorporating calcium borate into the glaze, which precipitates or segregates within the glaze. That is what I intend to follow out. The line of inquiry will be changed from time to time as results from the kiln warrant. I do not believe that B2O3 can take the place of AlgO-j, or that it will act as ALOo does. In nature, in all the boracic acid minerals, BoO-; takes tlie part of an acid. Mr. Humphreys : I will ask Mr. Stull what form of whiting he used. I think that is important in comparing with bone ash for temperature. In some recent experi- A CHEAP ENAMKL lOR STONEWARE. 13 meuts I found as much as a dittereuce of two cones in the different whitings. Mr. l^titU: I am not prepared to say where it was obtained. 1 found it in the laboratory there. Mr. Piirdi/: The whiting was ordered from the Illi- nois Supply Co., East St. Louis. Mr. Mayer: Mr. President, I was not present when all the paper was read, but I heard him mention colemanite. I made some experiments with some colemanite, the analy- sis of which was : B2O, 54.80 CaO 29.50 H2O 13.50 Carbonate .K: Sulphate of Lime and Silica 2.00 99.80 The experinsents were made with a raw glaze of ex- actly the same composition of the fritted glaze we were using right along. The note I made was, ''good glaze, ap- parently as good, as brilliant as the ordinary glaze, suits colors as well as our regular glaze." It was much better color than our own glaze. I have experimented largely with different forms of colemanite. There is only one dis- couraging feature and that is we cannot buy it cheaper than borax and boracic acid. Did Mr. Stull ask the price of this colemanite? I found that the trouble. We could get any amount of it and extremely pure, very little im- purity in it — white as snow; but they want an unearthly price for it. 1 did not get mine from the Pacific Coast Borax Co. I got it from a firm that had just found some deposits of extreme purit^v. The only trouble is the high price the people want for it. In practice they make glazes identically the same. I have not seen any peculiarity about it. Mr. Binns: I will ask Mr. Mayer if he dehydrated the colemanite? 14 A CHEAP ENAMEL FOR STONEWARE. Mr. Maijer: 1 just used the colemanite as it comes from the mines. 3Ir. Bijuis : And you did not experience the trouble Mr. Stull had on account of the pulverizing of the glaze? Mr. Mayer: I never had any such experience, and 1 used colemanite from three different firms. The last one I experimented Avith was an extremely pure sample. I never saw that difficulty in any of them. It is extremely hard, very difficult to grind. I broke several mortars before I learned how to break it up. Mr. Bill IIS : Although not germane to this discussion, Mr. Chairman, I want to speak concerning Mr. Stull's last statement. In mineralogy' there is one case of boron as a base, as I said yesterday. Datolite is a silicate of boron and calcium. The claim which I made yesterday was for boron in the presence of silica, which must not be ignored. I granted that boron acted as an acid in the presence of bases. I am interested in Mr. Stull's optimism when he thinks the difficulty of leadless glazes may be solved by the use of colemanite. T do not think the difficulty of a leadless glaze lies in the expense of fritting, rather in the manipula- tion of the process. I am interested in the development of the use of bone ash, and there are one or two points which seem to me need more light. My experience has been rather on the line of Mr. Purdy's', that bone ash is danger- ous to use. If intended to be used on a large scale, on a large mass of ware, that is where the trouble would come in. I will ask Mr. Stull in that connection what his ex- perience was in calcining bone ash with flint ; to what tem- perature he took it ; what he tried to accomplish, and if he thinks he accomplished his purpose? Mr. Stull : Answering Mr. Mayer's question, these experiments were carried out on the strength of the new deposit which has been discovered, and I am told that the Pacific Coast Borax Co. have carloads of it. The represen- tative of this company said, in answer to a question, that they could furnish it, but I do not know at what price. I A CHEAP ENAMEL FOR STONEWARE. 16 have not gotten the price yet. As I stated, we will have to investigate the matter of price. The mineral which Mr. Mayer speaks of as colemanite is not colemanite, but j)artially dehydrated colemanite. It is of the same composition as colmanite except that it is l)artiall3' dehydrated. There is a deposit in Oregon of this dehydrated colemanite. That, of course, being partly dehy- drated would not decrejjitate and would not give the trouble I experienced with colemanite, the trouble of the true mineral colemanite which contains 21.90% HoO. Keplying to Mr. Binns' inquiry in regard to the use of bone ash, my experience is limited to this case. I had no trouble at all. I made three burns, six, eight and nine, and in no case did I run into blistering. The great diffi- culty I had with the raw bone ash was that it flaked off badly. It fell off by itself in the drying. The idea of cal- cining it with flint was that in the manufacture of bone china it is often found necessary to recalcine bone ash to prevent blistering, etc., and I thought it best to recalcine it with a little flint and grind it and use it in that form. There was no special reason except to get a soft mass — not to burn too hard, though it would not harden by itself. Mr. Binns : I was born and raised on bone china and that is news to me. The calcining of feldspar, without producing any chemical change produces a physical change; but I did not see how the calcining of bone ash could have any effect, as it has already been calcined. Mr. ^StaU : I do not know anything about bone china, never saw it made ; and as I said, my only experience in the use of bone ash was in this case. Professor Bleininger sug- gested calcining it for that reason, and I think the German literature has something about the calcining of bone ash as obtained from the dealer, and gives instances where the trouble was overcome by recalcining. Mr. Mayer: Mr. Stull says the colemanite I got was not colemanite. I am not a mineralogist and do not pretend to know about these things, but I give you the name they call it. The}^ sometimes call it "pandermite'' and some- 16 A CHEAP ENAMEL FOR STONEWARE. times colenianite. I caimot tell the difference. I know it had 13.50% water in it. That I will vouch for. I think the man Avho gave me the sample is as much of a mineralo- gist as I am, and he sometimes calls it pandermite and sometimes colenianite. But it gave excellent results. The price nmde it simply out of the question to use. Air. BJeiiiinger: The main object of Mr. Stull's ex- periments is twofold, — one practical and one more theo- retical. The practical object is to obtain a cheap stoneware glaze for a certain type of stoneware. The second is to make large and extensive experiments which will tend to shoAv the various opacifying agents. Therefore, he has undertaken the work to show how the various opacifying agents behave and produce workable glazes. Mr. Bbins : Tf Mr. Mayer's glazing was done on bis- cuit ware and Mr. Stull's on green ware, it may be i30ssible that the combined water in the clay may have caused de- crepitation. Mr. Still] : It occurred before the kiln was red enough to see the cone. May I ask Mr. Mayer what percent of water was in the dehydrated colemanite he used? Mr. Mayer: The composition of the glaze in which 1 used this colemanite was : Feldspar 271 . 7 White Lead 105 . Florida Clay 59.2 Colmanite 150.0 Whiting 44.8 Flint 139.6 Mr. StuU: In pure colmanite there is 21.90% HoO. I will ask Mr. Mayer what was the percent of water in his variety? Mr. Mayer: 13.50 of water. Mr. StuU: It was probably half way between hy- drated and dehvdrated colmanite. A CHEAP ENAMEL FOR STONEWARE. 17 *COXTIXUATIOX OF THE WORK. The next step decided upon was to make up several glazes represeutiug five different series, determine their softening temperatures in the form of cones, group these glazes according. to their softening temperatures and fire them accordingly. 8ince the glazes in series IV in which raw colemanite was used powdered from the trial pieces, series V was made according to the respective formulae in series IV, the only difference being that the colemanite was dehydrated. ^EKIE8 VI, VII AND VIII. These series were constructed for the uprpose of de- termining the effect of increasing AI0O3 and PoO.^ by the use of aluminum pliosphate in the presence of calcined bone ash and B2O3. Since the sample of colemanite at hand was exhausted in making series V, and since letters to two borax compan- ies brought replies that they had no colemanite for sale as it was all absorbed by their plants in the refining of borax and boracic acid, it was decided to make a fritt after the dehydrated colemanite formula for use in the three follow- ing series. This was designated "Fritt B." Fritt B. Batch Weights : Formula Whiting 50 2 CaO, 3 B0O3 Boracic Acid 93 A preliminary test in the Pelton electric furnace shows that this mixture swells at 700° C to a porous sponge- like mass and melts to a clear, water-like fluid at 950°C. An attempt to make a drop fritt of this mixture had to be abandoned on accoutn of its great fluidity and corrosive action. It soaked through the fire clay crucible, draining *This installment represents the work which has been done on "A Cheap Enamel for Stoneware," between the last convention and the date of publication. o 3jn)EJ3dUJ3J, Suiuaijos o o o o O fx t^ t^ C^ >-H O o o o\ Percentage Batch Weights. 1"!U i 00 ■* -^ CO ro d 00 vo -4 (^ 01 M M l-l " UI|0E>1 EI3J030 \0 M t^ ! GO ^ d HH M 01 <^ V aupiEO ceo On 00' 00 01 CN) w 1-1 M M NO WOO 000 IT; (\) IN.VO Ln 1^ t^NO 'O NO VO in in in in Tt -^ JEdSp[3j aujMXpuEjg ■^ Tj- (^ t*5 CO fO M t-t HH l-t HH h-t 00 Tf CO in NO CONO ON roNO no" in 4 Tl- ro CO CO CO ro fO On ^000 0^ '^^oo m 01 On 10 in Tf- T:f rf CO 01 01 01 01 01 N On On On On On On O rONO On 01 m M hH i-i w 01 01 CO m CO ro fO CO o ro f^^ rO CO CO <^* O "^NO txOO On 000000 A CHEAP ENAMEL FOR STONEWARE. 19 U 3UIU3JJOS o o IT) (-0 o o O 1-1 C^l ro In, 0\ O O O O O O pg djEdsoqj lunuiianiv UJIOEJI E13JOJO jEdsppj JUI.U.ipUEJiJ 0< PO lO t^ ON >0 ^ "O "", ii~, lO i~^ rx\o ^o vd vo 01 ^) | 0) en 01 N N o oi o >-i '^1 '^- "t « 0) 04 O) 01 0) 660666 ! • 3jnjEJ3dUI3X auniayos 0) t^ "^ icvO X ^ >o 0\ On On '53 u bo S Oh ajeqdsoqd uinuiiuniv • CM^ ir, • f^i ^ ir, i^ c, JUIIJ 1- ic "-. " C\ O\o T " OnO 01 ^) 01 '^1 — M uiioEJi Etfjoao 1-1 li-; i-i t^ Tf ^ 01 i-c OnX j^ ujja X -i-\o >^ -r|- ON li-, >-i OsX \0 -t <^ 01 1 ^ I X I^ t-x t^ t^ t— 5 1— 1 1— 1 > W H- 1 W Formulae. 000000 a! - " - 6 CO i/~, LT, LT. ir-, li-, i/-, I^ 1^ I^ w t>, 1^ 01 01 01 fvi 01 '^^ q f^-O 0\ ^ '^■ 'I- 't ■* "^ "~' "P <3. t^ t^ tx t% t^ t^ ^ --^-"?^.^-^ N '^^P^ tN.x a, 1-1 <^ 0) OJ 0< CM 660606 20 A CHEAP ENAilEL FOR STONEWARE. out at the bottom like water through a sponge, and in a short time dissolved the bottom from the crucible com- l^letely. In order to increase viscosity and reduce corrosive action, ''fritt C" was constructed having the formula : FRITT C, BATCH WEIGHTS. .3 KoO ) (1.8 SiOs Brandy wine Feldspar 46.26 [ .3 Al:03 ] i.o B,03 Whiting 18.46 .7 CaO j { .011 P2O, Flaky Boracic x\cid 34.33 ^ ,. . . ,, ^ Bone Ash 95 Combming weight — 277.6 This mixture gave a very satisfactory drop fritt, very white and translucent. This fritt was used in making the three following series : SERIES IX. In this series the RO and acid were kept constant in order to note the effect of increasing the AUOo by using calcined Georgia kaolin. The glaze selected for the lirst member in this series has the formula : No. 30 .2 K2O) i2.5 Si02 2 ZnO\ .4 ALO3 .2 P2O5 .6 CaO) / .8 B2O3 A trial fritt marked "Fritt D" composed of bone ash, whiting and boracic acid was tested. Its formula and batch weights are: FRITT D. Formula. Batch Weight.s. pp. Bone Ash 28.94 I . CaO I /;^ ,^:'^A n Whiting 9.34 U.33 1-3 i3,U3 pij^j^y Boracic Acid 61.72 A portion of this mix when tested in the Pelton fur- nace softened at 760° C and fused to a thick viscous paste at 11G5°C. On testing for solubility in hot water, it was found that the B2O3 dissolved readily, leaving a fine white paste of bone ash and calcium borate. This shows the stability of bone ash in the presence of B2O3, since no u 3UIU3JJOS 0\ r-. ON O fN HH 0\ 0\ 0\ o o o Ph lUIIJ 0) i-h' 6 O'.od t^ U!IOE>i EI3J030 On -t U-. i^,X 1-1 ro 0< O 00 lO IT) \d 00 d " f^ in UIIOE>| EtajOJO rovO O -t t^ 1-1 ■^ ro fO IN 1-1 1-1 tN. t^ (N. t^ l>. 1>N 5 c o o u apixo 3UIZ <^ w 0\ t^ ""' r^ fo fo 0) ^^ N M r>i oi c>i N oi m' {^^ OO 0\0 CC OC X OC OC 00 01 "^l M (M M W ir, tn in \n \n iri 01 01 N W N M I— I CO W 2 CO < O rCNO 0\ 01 lO -t -)- -t ^ u-i lO o 01 01 01 01 01 01 ■ U VO O O NO^O o o 01 0) 01 01 01 01 . O »-i 01 ro •* in c^ ro f^ fO f^ f^ o c o o o o o 22 A CHEAP ENAMEI, POR STONEWARE. chemical arrangement took place, except the formation of calcium borate with the free CaO from whiting. On account of its solubility, fritt D could not be used. Instead, fritt E was made. FRITT E. Formula. .262-3 K2O ) I 1.6 Si02 .60 CaO L262-3 AUOa .2 P0O5 .131-3 ZnO i ( 1.062-3 B.O3 Cmbining weight— 295.733 Batch Weights. Brandy wine Feldspar 42.01 Bone Ash 17-53 Zinc Oxide 3 . 05 Flaky Boracic Acid 37-41 This mixtiiie makes a beautiful drop fritt ; white and opaque, resembling a tin fritt in appearance, and is prac- tically insoluble. The softening temperatures of all the glazes in series Y, VI, VII, VIII and IX were determined by the Le Chatelier pyrometer in the Pelton furnace, the softening points of each series being determined separately. These glazes were then arranged according to their bending tem- peratures for burning. No. 14c being softest and No. 19 the most refractory. As arranged in the table, all glazes softening between 950 °C and 1027 °C were fired at cones 03 and 01. Those softening between 1027° C and 1120° G were burned at cone 2, while those bending between 1033 °C and 1161 °C were fired at cones 1 and 6. Leu gill of Time of Buriiiuf/. Cone 03 was made in 9 hours. Cone 01 was made in 11 hours. Cone 2 was made in 18 hours. Cone 4 was made in 17 hours. Cone 6 was made in 19 hours. Coke being used as fuel. A CHEAP ENAMEL FOR STONEWARE. 23 Glaze °C No. 14c 953^ No. 25 952 No. 26 967 No. 31 976 No. 27 980] No. 30 991/ No. 14X 99-^ No. 32 996\ Fired at No. I2C 1000 , Cones 03 & 01 Mo. S3 1001 No. 20 ioio\ No. 35 loir No. 21 1025 No. 34 1026 No. 12X 1027 No. 13X 1027^ No. 22 1033 / No. 28 1 040 1 I No. 29 1050 I V Fired at No. 23 1070/ / Cone 2 No. iiX 1077' I g"-24 1090' \ pi,,j ,t No. IOC ii20i ; /^^„„^ . p K No. loX 1120, / ^°"'^ 4& 6 No. 16 ii37\ No. 17 1155] No. 15 1145I No. 18 11551 No. 19 1161/ In each cnse after firiiiii' was finished, (he fire was drawn, tlie fii'e box door and damper left open and the kiln allowed to cool quickly. Ari'EAKANCE OF THE TKIAL^. Series V. No. lOX. Cone '2: White, smooth, no l)eadin<^-; imder- fired. Cone 4 — (,>aite white and opaipie, slightly beaded, crazed some. Cone 6 — Opalescent, blisters where thick, crazed. No beading. No. 11 X. Cone 2: Opalescent, crazed, otherwise a good glaze. 24 A CHEAP ENAMEL FOR STONEWARE. Cone 4 — A good clear bright glaze. Opalescent where thick, no crazing. Cone 6 — Appearance same as at cone 4 except runs more. No. 12X. Cone 03 : Glaze somewhat immature, smooth. Cone 01— Bright and opalescent, slightly beads, crazed. Cone 2 — Bi-ight, less opalescent, smooth, no crazing. No. 13X. Cone 03 : Underfired, matt. Cone 01 — Bright, opalescent, beads a little, crazes. Cone 2 — Bright, opalescent, beads a little, no crazing. No. 14X. Cone 03 : Opalescent, bright, crazed some, no beading. Cone 01— Clear, bright, a few craze marks, no bead- ing. Series VI. In both the cone 4 and (> l)urns there is a gradual gradation in this series from IOC to 10. All are whiter in the cone 4 burn than in the cone burn. IOC is opalescent, blisters, crawls very slightly, has no crazing. Whiteness, opacity, crawling and crazing increase and blistering de- creases from IOC to 19. No. 19 is as white as a tin enamel, though some beaded and crazed. Series VII. No. 12C, Cone 03 : White, opalescent, tendency to bead, crazed. Cone 01 — Bright, opalescent. Beads some, crazes some. A CHEAP ENAMEL FOR STONEWARE. 26 No. 20. Cone 03 : White, opaque, crawls some, blisters some, crazed a little. Cone 01 — Translucent, crawls less, blisters some, crazes less. No. 21. Cone 03 : AVhite, opaque, beaded badly, crazes badly. Cone 01 — White, opaque, beads, crazes, no blistering. No. 22. Cone 2: White, opaque, beaded, crazed and blistered. Cone 4 — Blisters, no crazing or beading; translucent. Cone G — Opalescent, blisters, no beading, no crazing. No. 23. Cone 2 : Blisters slightly, beads and crazes. Cone 4 — Blisters slightly, white, no crazing; beads some. ('one (> — Opalescent, blisters, no crazing or beading. No. 24. ( -one 2 : Badly blistered, slight beading, badly crazed. Cone 4 — Whitest glaze of series. Blisters, no crazing or beading. (^one 6 — Appearance same as in cone 4 burn. Series VIII. No. 14C. Cone 03: Opalescent, crazes, otherwise good. Cone 01 — Same as the cone 03 burn. No. 25. Cone 03 : Translucent, crazes, otherwise good. Cone 01 — Opalescent, smooth, bright and crazed. 26 A CHEAP ENAMEL FOR STONEWARE. No. 26. Cone 03 : Translucent, whiter than 25, blisters, crazes. Cone 01 — Opalescent, smooth, bright and crazed. Slight beading. No. 27. Cone 03 : Translucent, whiter than 26, crazes, no beading. Cone 01 — Translucent, crazed and beaded. No. 28. Cone 2 : White, opaque, beaded some, crazed, no blistering. Cone 4 — Blistered, crazed, no beading. Cone 6 — Opalescent, blistered, no crazing or beading. No. 29. Cone 2 : White, opaque, beaded, blistered some, crazed. Cone 4 — Blistered badly, crazed, no beading. Cone 6 — Blistered, translucent, no crazing or beading. Series IX. Cone 03 — This series has given the best results so far. All are white, opaque, though crazed. No. 30 quite badly crazing decreases toward No. 35 which has only three or four craze marks. There is very little difference in this series in whiteness, opacity and brilliancy. The glazes, however, are not at their best, a little higher temperature would improve them. None are blistered. There is a very slight tendency to crawl in No. 30 which appears less in 35. Cone 01 — All the members of the series are beautiful opaque glossy enamels. The appearance is a light ivory in color and texture. No evidence of blistering. No. 30 is crazed slightly ; crazing decreases toward 35. Nos. 34 and 35 are not crazed though the body is very soft. Trials were also taken from the kiln quite hot. There is a \evy slight A CHEAP ENAMEL FOR STONEWARE. 27 28 A CHEAP ENAMEL FOR STONEWARE. tendency in all members to crawl a little in one or two small spots on the outside rim near the shoulder. The insides of the crocks are smooth and practically flawless, aside from those members (Nos. 30, 31, 32, and 33) which crazed. Brilliancy and opacity equal to a good tin enamel, color very nearly as good. An interesting point noticed both in the cone 03 and 01 burns is that the tendency to crawl in No. 35 containing .55 AI2O3 is less than in No. 30 containing .40 AI2O3, all other members in both remaining constant. The crawling tendency, however, is no greater than that of many good stoneware glazes and tin enamels in commercial use in which raw borax is used to overcome that trouble. Therefore, the enamels of Series IX are very promising, since they contain no raw borax or other soluble salts. CONCLUSIONS. Series I. In this series ZnO causes greater fusibility than BaO. Replacement of BaO by ZnO reduces crazing, increases brilliancy and opacity. Series II and III. The use of bone ash direct causes flaking of the glaze after dipping. Flaking is overcome by calcining the bone ash with flint. Replacement of CaO from whiting by CaO from bone ash increases refractoriness materially and induces crazing. .131/3 P2^5 introduced as bone ash with .3 ZnO and .4 AI2O3 caused no beading and materiall}' increased AAliite- ness. A CHEAP ENAMEL FOR STONEWARE. 29 Series IV and V. The use of raw coleiiiaiiite* in glazes causes "powder- ing" before a dull red heat is reached. Powdering is over- come by using dehydrated colenianite. Replacement of bone ash, ZnO and SiOs by dehydrated colemanite, materially decreases the temperature of fusion, decreases opacity and increases brilliancy. The opacifying effect of colenianite is very small, pro- ducing at best onl}^ a small degree of opalescence. faeries VT, VII and VI IT. It is tlifticult lo determine (he action of aluminum phosphate in these tliree series. Increasing AI2O3 and P^.O., by alnminum plios])hate increases the temperature of fusion a little, increases whiteness and opacity. The blistering which occin-s has the appearance of being what "single fire" enamel brick men call "steamed glazes.'' Opacity, whiteness, blistering, beading and craz- ing generally seem to be lessened by increase in tempera- ture of firing, though not borne out in all cases. None of the glazes containing aluminum phosphate are good enough for commercial use. It is probable that more consistent results would have been obtained if the aluminum phos- phate had been calcined or fritted. Series IX. This series shows that good glossy enamels are possible as low as cone 01 with : 2.5 Si02 .2 ZnO .6 CaO . .2 K2O \ .40 to .55 AI2O; 1 2.5 SlO: \ .2 P2O j .8 B2O: *A distinction should be made between the three most general forms of calcium borate, viz., colemanite, priceite, and pandermite, which have different physical properties such as hardness, specific gravity, action before the blow pipe, etc., as well as differences in their respective chemical analyses. However, both priceite and pandermite are classed as "varieties'" under colemanite by mineralogists. 30 A CHEAP ENAMEL FOR STONEWARE. in which bone ash has been calcined or fritted and in which the excess above .3 AI2O3 is added as calcined clay. Experiments with bone ash as an opacifier in glazes are not new, yet the author fails to find any work in ceramic literature pertaining to its use purely as a glaze ingredient aside from its uses in glass and bone china. The question has been raised that bone ash is dangerous to use in glazes on account of its liability to cause beading. It is a well known fact that an excess of the opacifiers, alumina, tin oxide, zinc oxide and bone ash causes beading. The observations of the writer ]ead him to believe that bone ash has no greater tendency to cause beading than ZnO, SnOs or ALO... If we attempt to add bone ash to a ghizo of the Bristol type, which is already loaded up with an opacifier, bringing it close to the danger point of beading, then of course beading will occur. This concludes the work to date. The next step will be to test the members of series IX for range of tempera- ture to determine whether they are suitable for commercial use. If so, then the best one of the series will be selected for the starting point of series X, in Avhich the BoOo is to be gradually replaced by SiOo in an endeavor to produce suitable "tinless" enamels for higher temperatures. THE VISCOSITY OF CLAY SLIPS. BY A. V. Bleixinger, Chanipaia:n, Illinois. The plasticit3' of cla^'^ is still a quality \vliose physical definition has not yet been established, though many at- tempts haye been made to do so. All v;e can do at present is to continue the search for some criterion Ayhich bears some relation to this elusiye property. Up to the present such i)ro]>erties of the clay as the tensile strength, both green and dry, its deformation, cru.shing strength in the green state, and also recently the yiscosity imparted to suspensions of clay particles haye been studied. This last [)roperty is promising inasmuch as it produces a plienonu^- non Ayhich is clearly not shared by non-plastic materials. hi fact, it mighf he f iche)) puJvcrizcd and suspended in irater itrodiiee a decided in- crease in viscosity.^ This yiscosity is cai»ab]c of being expressed numeri- cally with a degree of accuracy \yhich is superior to that of any of the methods mentioned aboye. Siinonis^ has measured the yiscosity by determining the yolume of a clay-slip flowing through an aperture of 2 mm., under constant pressure, in a giyen time. A mar- iotte flask was used to maintain constant pressure in the burette containing the slip. The burette was first stand- ardized Ayith water and the relation existing between the yolume flowing from the tube and the pressure obtained. This relation is eyidently A'^kp, where y=yolume of liquid discharged in a giyen time, p=pressure of the liquid or its height in the yessel, and k^^coefificient of fluidity or the yiscosity. Solying for k we obtain k=^-p If now the pres- sures are plotted along the abscissa and the yolumes es- 'Sprechsaal, 1905, 597. 31 32 THE VISCOSITY OF CLAY SLIPS. caping, along the ordinate we obtain for ideal liquids straight lines where -^ is equal to the coeflQcient of fluidity represented by the tangent of the angle made by the line to the X axis. In the case of da}' slips Simonis found the relation to be not so simj^le and he obtained as the functions of vol- ume and .pressure, curves of higher degree. The siiuie in- vestigator, having found considerable difficulty witli this method in working thick slips, devised a second method for determining the cohesion of clay slips by measuring the weight necessary to pull away a 5 cm. glass plate from the surface of the liquid. For this purpose he arranged a bal- ance, having the glass disc attached at one end of the beam and a scale pan at the other. He caused very fine shot to pour onto the pan, arranging at the same time an auto- matic shut-off device. Before working with clay slips he determined the weight necessary to pull away the disc from water. Applying the test to cla^' suspensions and noting the weight necessary to release the disc he subtracted from this load the weight required to pull away the glass from water, which is a constant factor. In this way the cohesion value of the clay for the concentration employed Avas de- termined. This method is applicable to thick slips which fail to give results by the flow method. There are faults inherent Avith both of these methods, the flow method being subject to irregularities caused by the roughening of the walls of the A'essel, the irregular stopping up of the aperture and other difficulties while the disc method is faultv as soon as even the slightest settling takes place. In looking about for a method which perhaps might overcome some of these difficulties the Coulomb method, as employed in the determination of the viscosity of oils, was considered and adopted. Although the apparatus as de- signed is not suitable for thick slips, some interesting results were obtained, and the ease and accuracy with which the viscosity of thin slips could be determined makes THE VISCOSITY OF CLAY SLIPS. 33 34 THE VISCOSITY OF CLAY SLIPS. it quite suitable for certaiu investigations. It lias afforded tlie writer a delicate means of distinguishing clays of dif- ferent plasticity, or of following the effects of electrolytes and organic substances upon the physical character of the clay suspensions. The apparatus itself is exceedingly simple, the disc being suspended from a steel wire 11 ft. 6 in. long, and allowed to rotate within a vessel filled with the clay slij), figure 1. At the center of the brass disc filled with lead, a rod pro- jects, provided with a clamp for gripping the wire firmly. An aluminum pointer is fastened to the rod which swings over a circular scale around the rim of the receptacle, grad- uated in degrees. This scale is made out of paper and var- nished. The weight of the disc is 1333 grams and the thickness of the wire 0.85 mm. In making the test the slip is first thoroughly stirred up and poured into the vessel. The disc is then turned about 180° by means of the pointer and released. The num- ber of degrees is read off at the turning point of the vibra- tion so that the amplitude of each swing in the same direc- tion is observed. This is continued until several readings have been taken. The disc is then stopped and the slip stirred up for another set of check readings. Tlie ratio of the amplitude of two successive swings is obtained by di- viding the first reading into tlie second, the second into the third, and so on. This ratio is a constant for the same slip at the same temperature. It is important to make note of the temperature, or better to keep it constant, since the viscosity of the water itself changes with change in tem- perature. The time of periodic vibration is obtained h\ taking the total of, say, ten complete vibrations and dividing by 20. It may also be calculated from the length of the wire. For the apparatus in question the periodic time of vibra- tion was found to be 3.6 seconds, thus enabling two ob- servers to make the readings quite readily. Knowing the period of oscillation and the ratio of the amplitudes we can calculate the viscosity of water and that THE VISCOSITY OF CLAY SLIPS. 35 of the slips to be compared with it. In this work the vis- cosity of water is always used as the standard, and hence the viscosities obtained are in terms of the viscosity of water. Several methods of calculation might be employed, based upon the laws of the dampenino- of vibrations. As- suming for instance that the ratio of the amplitudes is O.S and the time is 1.5 seconds for each vibration, we obtain as an expression for the viscosity of the liquid : 0.8=e-i 5k or —log 0.8=1.5k log e. Then K==^?^-' =0.15 1.5 log e If in another slip the ratio of the amplitudes is found to be equal to 0.7 and solving again for K Ave obtain 0.24. The viscosities of the two liquids, therefore, are to each other in the ratio of 15: 24. A somewhat sim]»ler relation might be used for determining the relative though, of course, not the absolute viscosities, in which Vi=coefficient of viscosity of one liquid: i'j=rratio of the amplitudes of any two successive os- cillations in the same direction in the same liquid ; Ti=period of oscillation ; di=dampening constant. Similarly let V2, r^, T^ and d^ be the corresponding values for the second liijuid. We have then the relation di To log Tj Vi do Ti log ro Vo This gives us K, a coefiicient of specific viscosity. The standard employed is distilled water whose ratio is de- termined at the same temperature as the ratio of the slips to be tested. The constant for water, of course, differs with different apparatus. In the experiments carried on in the apparatus described it was 0.89. It was decided to make viscosity determinations with three kaolins which differ widely in their physical behavior. 36 THE VISCOSITY OF CLAY SUPS. The method obviously is not intended for clays which are coarse-grained, and if they are to be tested in this way the coarser portion must be screened off. The three clays se- TRANS. AM. CER. 50C . VOLX Bl_E.I(MIN&ER II |a.o 1.9 O /.6 Si.. 1.4 ,/.3 <« 1.2. o ."^ i.l 1.0 t o^)^4o 7.~ TenaBallC T=I9»C, F :.-,i / / / / / Flor T=2I idaK °C aoliny / J > / / > / y X' x N.C.K ao\\n, ^^ -'^i "^^ 94^ " " , — ■ — ^ 3 4 5 6 7 8 9 Percent oSClaij By Weight. 10 U \Z »3 i4 /5 THE VISCOSITY OF CLAY SLIPS. 37 lected were the Xortli Carolina kaolin, Florida kaolin, and the Tennessee ball clay, Xo. 7. The c-lavs were wei '^ 1 S3 U. "J \ N \ X • u. \ o > V d o — ^ tc. Ill ,J o < r / ^ y < <=>o o o O Sec ^ O CL. 3^niVy3dN3± 42 NOTE ON SOME FUSION CURVES. served by means of an opera glass. Unfortunately some of the cones Avere cracked in drying due to an excess of dex- trine and broke off in the kiln. These were not considered in the result. In Fig. 1 we have shown the fusion curve of the feld- spar-ferric oxide series, and a eutectic is clearly indicated with 91% feldspar and 9% of iron oxide. This mixture corresponds to the formula : 0.015 MgO 0.034 CaO 0.766 K,0 0.185 ^'aoO The feldspai- formula is represented by the same for- mula but without the iron. This mixture therefore fuses at a lower temperature than the feldspar itself or any other mixture of the series. In Fig. 2 the feldspar-lime series is not complete owing to the breaking of some of the cones, and hence the eutectic point is not definitely established, but it is quite evident that it is close to 97 7^ feldspar, S^c whiting. This would correspond to a slight enriching of the spar in lime corresponding to about 0.03 equivalent. Since this point was not determined with certainty no interest is attached to its formula. In Fig. 3 there are plotted the compositions of the mixtures in terms of the percentages of feldspar, iron-oxide and whiting, and it is evident that the isothermal composi- tions are connected by some definite law. Each curve represents a temperature interval of 20°, correspond- ing to the range of one cone. Thus every mixture in the inner area melted between 1175° and 1195''C. The increase in area indicates the enriching of the fusion by the solution of other materials on raising the temperature, and ^^e learn thus in what direction this takes place. Similar curves carried on very carefully with pure lead silicates, fusing the cones in an electric furnace, showed some disturbing factor owing to volatilization of the lead, and hence are not produced. This trouble was XOTE ON SOME FUSION CURVES. 43 , TRANS. AM CER. SOC VOL BLEININCER 1200 Q!:|150 MOO FIG 2.. FUSION CURVE FELDSPAR-LIME SERIES. - "\ . / 1 / 1 WHITING 100 FELDSPAR 5 10 55 90 °iO COMPOSITION 15 85 TRANS *vi CtR SOC VOL PIG 3 BLEINlNGEf^. 44 NOTE ON SOME FUSION CURVES. encountered even with fritted glasses, and the work is to be rejieated under speeial precautions. DISCUSSION. 77?c Chair: I think Professor Bleininger has given us a splendid paper, and I am very glad to know that he is getting near to the practical man. I will call on Mr. Stover, as a practical man, to discuss the paper. Mr. I^torer: I would like to ask Professor Bleininger why he expressed the data in percentage weights? Mr. Blciiiiiifjcr: Because it was the simplest way. .1//". ^Stovcr : I don't want to say a word against the use of technical formulae, for I sat up many nights in order to master it so I could figure them out by myself; but it is a fact that I have been arguing along the line of this sort of expression without much result until at this meeting. I have contended it would make it more simple, and if we could have the kind of data Mr. Bleininger has been trying to give us lying around in the mixing room^i of the practical potters in Trenton and East Liverpool, we wouhl have something here in the pages of the proceedings which would be of practical value. But for the most part, we are soaring around ovei* their heads and they cannot understand us. I am glad Professor Bleininger has put bis data in plain percentages, for T believe it will be productive of practical results. lite Cliair: I want to say, as a practical man, that I am impressed witli the fact that we are getting closer and closer to the practical man in our work. There are many things about the technical part of the American Ceramic Society's work which the practical man cannot understand ; but he realizes the meat is there even though he cannot always digest it. I think this is a simple method and that the practical man will by and by conclude that after all there is something in pottery worth knowing that he does not understand. ^■^ {^.'^ i*^* m< l.*»^ ?^^#^.,>^ L^<^-i^ .> ^ ' j'f -?r.' ^::^i^^ ■^. \^ UNIVERSITY OF ILLINOIS-URBANA 3 0112 052567101 ^tk*^;# f-M ' '•' ;-,'%, ^-&T