I 
 
 PRESERVATIVE TREATMENT OE WINDOW SASH 
 
 AND OTHER MIEEWCRK 
 
 ffO" ES,T 4 * ERV) ct] 
 
 \2nll 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 
 FOREST SERVICE 
 FOREST PRODUCTS LABORATORY 
 Madison, Wisconsin 
 
 In Cooperation with the University of Wisconsin 
 Revised, April 1938 
 
 ?.. - 
 
 \^s- 
 
 - m/k>/<// 
 
Digitized by the Internet Archive 
 
 in 2013 
 
 http://archive.org/details/preseaOOfore 
 
PH3SSRVATIVE TREATMENT OP 
 WINDOW SASH AHD OTHER MIILWORK 
 
 By 
 
 George M* Hunt, In Charge, 
 Section of Wood Preservation* 
 
 How important is decay resistance in woods used for window 
 sash? How important is it in frames, shutters, floors, and millwork in 
 general? These items are not commonly destroyed "by decay because the 
 conditions under which they are placed are not favorable to deterioration* 
 The average owner or occupant of a dwelling, store, or office "building 
 seldom encounters an instance of decay in the sash or interior woodwork 
 of the "building* On the other hand, every manufacturer of wooden window 
 sash or frames and every carpenter who does repairing can point to 
 numerous instances of replacement made necessary by decay. 
 
 The total number of wooden frames, sash, and shutters manu- 
 factured in a year is in the millions* No statistics on the number that 
 show decay under ordinary use conditions are available; an expensive 
 and time-consuming survey would be required to furnish a satisfactory 
 basis for merely an approximate estimate* Probably, however, the per- 
 centage is small* Yet, although the number of instances of decay may be 
 low, the matter cannot be ignored* It is far from immaterial to those 
 who have to pay for expensive repairs caused by premature decay, and the 
 manufacturer who loses the business or the good will of these displeased 
 customers can hardly afford to consider it trivial* On the other hand* 
 it is hard, without definite information as to the extent of the need, 
 to justify any marked increase in cost of all sash and frames to protect 
 the small percentage that may need it. 
 
 A factor of some importance is the modern trend towards air 
 humidification and tighter window construction, especially in the colder 
 parts of the country. Both favor the maintenance of higher humidities 
 xn buildings in the winter than have been customary in the past, which 
 encourages the condensation of moisture on windows in cold weather and 
 tho collection of moisture in walls* It is reasonable, therefore, to 
 
 R919 
 
expect an increase in the amount of trouble from decay as well as from sap 
 stain in windows, beyond what has taken place in the past.— 
 
 In industrial buildings of certain types, where it is known from 
 experience that sash and other woodwork will be subject to decay on account 
 of the service conditions, there is no question that decay resistance 
 should be provided. Experience has shown that the use of metal sash is not 
 a satisfactory solution of this problem in industrial buildings where high 
 humidities prevail, especially if there is any acid in the air, but wood 
 sash thoroughly impregnated with a good preservative have been shown to 
 be very durable in such places. All-heart sash of highly decay-resistant 
 woods that are suitable in other respects may also be used successfully. 
 
 In the competition between wood and metal sash for dwellings and 
 office buildings, lack of decay resistance in untreated wood sash is a 
 sales disadvantage for wood that its* competitors have not neglected, and 
 the wood sash manufacturers can afford to make some attempt to overcome 
 this obstacle. Tor this reason, as well as to reduce the number of cases 
 in which decay or staining takes place, the treatment of all sash made 
 from wood of low decay resistance has much to recommend it, providing it 
 can be done effectively at moderate cost. 
 
 The Relative Decay Resistance of the Soft Fines 
 
 A question frequently asked is how the various pines now used^ 
 for sash compare with one another in decay resistance. The question arises 
 in part from the desire of the manufacturer and the user to know more about 
 the subject, and in part, no doubt, from the conflicting claims made by 
 the promoters of competing species. As a matter of general knowledge it 
 would indeed be interesting to know just how northern white pine (Pinus 
 strobus ) , western white pine ("Idaho white pine," Pinus monticola ), sugar 
 pine ( Pinus lambertiana ) i and ponderosa pine ( Pinus ponderosa ) compare 
 with one another in average decay resistance. Since these woods, when un- 
 treated, are not ordinarily used in contact with the ground or in other 
 places where conditions are known to favor decay, there are no adequate 
 service records on which to judge them. Furthermore, they have not built 
 up a body of experience and general knowledge of their decay resistance 
 
 -In the northern part of the country the use of storm windows will often do 
 much to reduce condensation on windows and the consequent danger of stain 
 and decay. Weather stripping is useful for reducing infiltration of air 
 around windows but it does not keep the glass from becoming cold enough 
 for condensation to gather. Storm windows, on the other hand, keep the 
 inside panes of glass much warmer and cut down loss of heat through the 
 windows. House owners should take care to see that they do not have 
 oxecssive condensation on their windows. When cooking, bathing, or 
 laundry work leads to condensation during cold weather, windows or doors 
 should be opened sufficiently to ventilate the house or the room and 
 carry out the excess moisture, even though a littlo more fuel may be 
 required, to knep tho- h/yiso warm. 
 
 R919 -2- 
 
such as that available on the woods more commonly used outdoors in 
 fences, pole lines, and railroad and other engineering structures. At- 
 tempts have "been made to work out laboratory methods for accurately com- 
 paring the decay resistance of different species but thus far none of the 
 suggested methods has been found acceptable* It is impracticable, there- 
 fore, to set up a table of relative decay resistance for these species 
 and defend it successfully, whatever one l s personal opinion may be* 
 
 Hear two od and Sapwood 
 
 A well-known fact about all the commercial woods of the United 
 States is that, under dry conditions, both the sapwood and heartwood 
 remain free from decay but, under damp conditions, the sapwood is not 
 resistant to decay, regardless of the durability of the heartwood* The 
 sapwood of such naturally durable species as redwood, cedar, and cypress 
 rots quickly under conditions that favor decay and so does that of the 
 pines and other species* Whether there is a measurable difference between 
 the decay resistance of the sapwood of a species having highly durable 
 heartwood, and the sapwood of one having less durable heartwood, has not 
 been established but, even if a slight difference does exist, it is not 
 enough to be significant* The outstanding fact is that, where decay re- 
 sistance is required, no sapwood should be permitted unless it has been 
 adequately treated with a toxic preservative* 
 
 There are no restrictions on sapwood in lumber used for 
 ordinary sash and frames. If used under conditions that are not con- 
 ducive to decay, their life is not affected by the presence of the sap- 
 wood* Under conditions favorable to fungus growth, however, the sapwood 
 invites early stain or decay, whether the heartwood is durable or not* 
 So long as the practice continues of allowing unlimited amounts of sap- 
 wood in window sash and frames, there is little point to the debate 
 over the relative decay resistance of the various pines that are now being 
 used for those purposes* If a sapwood corner rots in a window sash or 
 if the sash lift pulls out because of decay it is small comfort to the 
 man who has to buy a new sash to know that the heartwood parts of the 
 discarded sash are still sound* 
 
 A defect often encountered in sash and frames and chargeable 
 to sapwood is the black or blue stain that develops when the wood takes 
 up moisture and remains damp for considerable periods of time. It is 
 merely a sap stain fungus growing after the installation of the finished 
 article in the house instead of growing while the lumber was in a yard* 
 The stain, when it occurs, is readily visible through varnish and fre- 
 quently breaks through varnish or paint, to the discomfiture of the 
 painter, who usually gets the blame* Since sap stains do not grow in 
 heartwood, this defect is found only when sapwood is present and then 
 only under damp conditions* While these stains do not destroy the wood 
 
 H919 -3- 
 
they may necessitate its removal on account of its appearance. They also 
 indicate that conditions are favorable to decay and should he corrected.— 
 
 In addition to the staining caused by fungi that grow in the 
 wood, molding or staining of the paint may occur that does not extend into 
 the wood. Such staining cannot be attributed to the wood, but it is an 
 indication that conditions are favorable for wood staining and decay and 
 that they should be corrected. 
 
 Improvement Through Selection of Wood 
 
 A simple way to provide high decay resistance (although not 
 necessarily the most practical or the most economical) is to make the 
 sash, frames, or shutters nut of naturally durable wood. The heartwood 
 of certain species high in decay resistance can usually be counted on for 
 long service even under conditions that favor decay. Then questions of 
 available supply, cost, appearance, working properties, and mechanical 
 properties are taken into account, however, these species do not have un- 
 disputed superiority over the woods now commonly used for sash and frames. 
 
 Protection Through Painting 
 
 Contrary to popular belief, paints and varnishes are not ef- 
 fective in preventing decay. Wood used under conditions that favor decay 
 can rot readily, whether it is painted or not. If paint could be relied 
 upon to prevent the absorption of moisture and thus keep the wood always 
 dry, decay would of course be prevented, for it is the presence of 
 moisture in considerable quantity that permits decay. Wood that is well 
 painted on all surfaces does absorb moisture more slowly than unpainted 
 wood but the absorption is not prevented entirely. It is seldom, however, 
 that wood is painted on all surfaces and moisture absorption is not re- 
 tarded in the least through the unpainted surfaces. Moisture can usually 
 find access also at joints, where the paint cracks because of repeated 
 dimension changes in the wood or the working of the joints. Moisture that 
 has found access to the interior of painted wood will evaporate more 
 slowly than from unpainted wood. When this happens the paint may favor 
 rat lie r than retard decay. 
 
 Paints and other finishes do not prevent the development of 
 blue stain* If conditions are favorable to the development of the blue 
 staining fungi they grow, regardless of the paint that may be over them* 
 If conditions are sufficiently favorable the staining fungi grow right 
 through paint or varnish and repainting does not prevent their reappear- 
 ance if the damp conditions are allowed to continue. Furthermore, as 
 previously stated, fungi may grow in the paint itself and cause discolor- 
 ation wi t.h out^e^anjiijTj^ the wood. 
 
 —Once the faulty condition has been corrected blue-stained sash may be 
 safely repainted provided they are first given time to dry out thor- 
 oughly. It may be desirable to remove the old paint before repainting* 
 
 B919 -4- 
 
Preservative Treatment 
 
 Preventing decay in wood by injecting toxic chemicals is easy* 
 Preservatives and methods of treatment have long been available that can 
 be relied upon to give to wood, even sapwood of low natural decay re- 
 sistance, very long life under the most severe decay exposure. They 
 will also prevent sap stain development* The problem of treating to 
 meet the special requirements of wood for use in window sash, frames, 
 and other millwork, however, is not easy of solution. For example, no 
 more effective preservative than coal tar creosote is known, but it is 
 obviously unsuitable for use in the windows or millwork of a house be- 
 cause both the color and odor of the creosote are objectionable, and 
 creosoted wood cannot be satisfactorily painted or varnished. 
 
 Water Borne Preservatives 
 
 There are several good preservatives that can be injected in 
 water solutions by pressure methods. Drying out the water after treat- 
 ment leaves the wood clean, odorless, and paintable, although often 
 changed in color to some extent. If the work is properly done and if 
 the pieces in any way degraded by the treatment and subsequent drying 
 are eliminated, the purchaser will receive a good product that is highly 
 resistant to decay. It is quite possible to produce well-treated frames 
 and sash in this way. The treatment is far from being as simple as it 
 sounds, however, and the inconvenience and expense involved have pre- 
 vented most sash and frame manufacturers from attempting to use water 
 borne preservatives. 
 
 Treatment of Lumber Before Milling 
 
 One procedure that may be followed in using water solutions is 
 to treat the lumber by a pressure method before cutting it up and mill- 
 ing it. When this is done the lumber must obviously be completely pene- 
 trated and the preservative should be distributed through it uniformly. 
 Spots of untreated or poorly treated wood in the interior of a board 
 will almost certainly.be exposed when the board is milled to finished 
 size and shape, and under conditions favorable to fungus growth these 
 vulnerable spots will be "welcome" signs to fungi. Complete penetration 
 in sapwood pieces of most species up to k inches in thickness should 
 offer little difficulty if pressure-treating equipment is available and 
 proper treating conditions are used. Excellent treatment can readily 
 be obtained, therefore, wherever it is possible to select for treatment 
 lumber that contains no hear two od.i. It is more difficult to obtain 
 
 <£The superiority of heartwood over sapwood in decay resistance when un- 
 treated is of no significance in wood that is properly treated, for 
 good preservatives properly injected prevent decay in both heartwood 
 and sapwood. 
 
 R919 -5- 
 
complete penetration in heartwood, but it is not impossible if the boards 
 are not too thick. Considerable difficulty is likely to be encountered 
 in completely penetrating heartwood pieces 2 inches thick or over. Dif- 
 ferent species of wood vary somewhat in the resistance of their heartwood 
 to treatment but in practically none of them can the heartv/ood be con- 
 sidered easy to treat* 
 
 Treatment if ter Milling 
 
 Preservative treatment may be applied to the finished frames 
 or sash after assembly, or to the individual finished pieces just before 
 assembly* Both periods of application have the advantage that complete 
 penetration is not necessary, for there will be little or no cutting 
 after treatment. When using water solutions, however, treatment after 
 assembly involves a number of difficulties. Injecting water into the 
 wood will make it swell, probably causing, in consequence, either actual 
 rupture of joints or at least compression severe enough to result in 
 open or loose joints on subsequent drying. The checking and distortion 
 that may develop in some of the assembled parts upon <irying will cost 
 more than a similar amount of warping or checking in the rough lumber 
 would cost. Any joints containing glue may be seriously affected by the 
 water and, furthermore, the surface of the wood may be so roughened that 
 resurfacing will be required. Altogether, the outlook for the treatment 
 of assembled sash with preservatives in water solution does not seem 
 bright but, in some cases, it may be found practical. Treatment of the 
 finished parts before assembly would not cause loose or open joints but 
 grain raising, warping, checking, and drying problems would still be 
 encountered. Undoubtedly, however, water borne preservatives can be 
 used to advantage under some conditions. 
 
 Special "Sash" Preservatives 
 
 During the past few years a number of proprietary preservatives 
 have been developed especially for the treatment of sash and similar pro- 
 ducts. Generally they consist of an organic toxic chemical carried in 
 a nonaqueous volatile solvent. They are practically colorless and dry 
 quickly by evaporation of the solvent. If of suitable character they 
 leave the wood clean, paintable, and practically odorless. 
 
 Various toxic chemicals have been used in these formulas, in- 
 cluding alphanitr ©naphthaline, betanaphthol, chlorbetanaphthol, chlor- 
 orthophenylphenol, metallic naphthenates, pentachlorphenol, and tetra- 
 chlorphenol. This list by no means exhausts the possibilities and it 
 is very probable that other toxicants will be found that are as good or 
 better. The relative merits of the toxicants named neve not yet been 
 worked out satisfactorily, but all seem to be sufficiently toxic to be 
 effective, provided they constitute not less than 5 percent of the treat- 
 ing solution (by weight). Since these toxicants differ in cost, odor, 
 solubility, and other properties it is to be expected that, as the 
 knowledge about them increases through research and experience, some 
 
 R919 -6- 
 
will be found more desirable than others. Considerable work in this field 
 is being done by the Western Pine Association, as well as by some sash 
 manufacturers and manufacturers of toxic chemicals, and a gradual change 
 and improvement in formulas is to be anticipated for some years to come. 
 
 In some formulas drying oils, such as linseed oil, have been 
 used for the purpose of "priming" the sash and making it water resistant. 
 This practice is not to be recommended, for it fails to give the sash 
 any material resistance to moisture or to provide an adequately primed 
 surface, but it may reduce the effectiveness of the toxic chemical. 
 Even dipping in pure linseed oil is not effective in priming or water- 
 proofing wood, and dipping in diluted solutions is less so. 
 
 Nondrying petroleum oils are sometimes advocated as an ingredient 
 of sash treating preservatives. It is possible that the addition of a 
 substantial amount of such oil may have an undesirable effect on paint or 
 putty subsequently applied to the treated sash. Considerable time and 
 experimenting will be required to determine the extent to which this 
 possible disadvantage actually exists. In the meantime, it is not en- 
 tirely safe to ignore it. 
 
 The degree of effectiveness of the special sash preservatives 
 in preventing decay, blue stain and insect attack has not been definitely 
 established. Laboratory experiments have indicated that they should 
 give good protection if the wood is properly impregnated with a substan- 
 tial quantity. It is believed, therefore, that the use of sash preserv- 
 atives is desirable. Long continued observation and experience with 
 treated sash under actual use conditions will be required, however, to 
 determine the extent to which the promise of the laboratory experiments 
 is borne out in actual service. 
 
 In order to choose intelligently among the various sash pre- 
 servatives it is important to know their composition. The terra "wood 
 preservative" is used very loosely by some makers of paint and varnish 
 materials and there are products on the market which have been recom- 
 mended for sash treatment that contain no toxic ingredients. Others 
 may contain ingredients that are not sufficiently effective or that are 
 present in insufficient quantity. Such materials cannot reasonably be 
 expected to afford satisfactory protection against decay or stain. A 
 secret formula leaves the purchaser without information as to the 
 presence of a toxic ingredient, its nature, or the amount present in the 
 solution, all of which are very important in considering the probable 
 effectiveness of the material. Furthermore, the composition of a secret 
 preservative may be changed at will by the manufacturer or seller, with- 
 out the knowledge of the consumer. When the composition is disclosed 
 the purchaser has something definite for consideration, both as to cost 
 and. probable effectiveness, and he may also make occasional analyses or 
 tests to determine whether the quality remains the same. Enough pre- 
 servatives of known composition are available to make it unnecessary for 
 anyone to purchase secret preservatives. 
 
 R919 -7- 
 
With a good preservative of this character, treatment can be 
 made after finishing the parts, either "before or after assembly. There 
 is no swelling of the wood and no drying out of moisture after treatment, 
 with its accompanying troubles. Penetration need not be complete but 
 it must be deep enough to insure against exposure of untreated wood when 
 the carpenter trims the frame or sash on installing it. Such exposure 
 can be avoided by fitting the sash to the frame in the factory and 
 treating after fitting. If the wood is sound to begin with, maintaining 
 a substantial depth of treatment at all surfaces and in all joints will 
 prevent decay or untreated wood that may be beneath. It is when the 
 treated area is broken through by cutting or checking or by the opening 
 of poorly treated joints that the untreated wood beneath can be reached 
 by the fungus. 
 
 Importance of Good Treatment 
 
 Obviously, good treatment is needed, in addition to a good pre- 
 servative, for even the best preservatives cannot give much protection 
 if not properly applied* Although complete penetration is not required 
 in treating finished parts, substantial penetration is necessary, re- 
 markable penetrating powers are not infrequently claimed for proprietary 
 treating oils so that a brief dipping treatment is often said to be 
 all that is required to give deep penetration with them. With a suit- 
 able preservative an appreciable amount of protection can no doubt be 
 obtained by a few minutes submersion but better penetration and con- 
 sequently better protection will be obtained by using longer soaking 
 periods or more thorough treating methods. The Western Pine Association 
 recommends an immersion period of not less than 3 minutes. This is long 
 enough to give a substantial degree of protection. Shorter periods are 
 undesirable and longer ones are to be preferred* 
 
 On account of the high volatility of most of the solvents 
 employed in special sash preservatives, it is usually impractical to 
 heat them* The effect of a hot-and-cold bath treatment can be accom- 
 plished by heating the wood in a properly controlled kiln and then 
 submerging it and allowing it to cool in a tank of cold preservative. 
 This method has been patented. A similar effect can be obtained by 
 placing the sash in a closed container, drawing a vacuum, and admitting 
 preservative without admitting air or applying additional pressure. 
 
 Branding Treated Sash 
 
 nee the special sash preservatives are practically colorless 
 it is very difficult and usually impractical to detect their presence 
 in the wood after the sash have been in service some time. It is very 
 desirable, therefore, that sash manufacturers place a permanent brand 
 cr identification mark on their products, giving the date and some mark 
 to identify the preservative and method of treatment. This will permit 
 failures to be traced to their sources and aid in pointing the way to 
 improvements. It will also be of value in identifying products that 
 give long and satisfactory service. 
 
 Kjl<j -8- 
 
Treatment for Industrial Buildings 
 
 In certain types of industrial buildings, where the require- 
 ments for appearance are not too strict and where it is certain that high 
 decay resistance is required, the problem of protecting sash and frames 
 is not so difficult as for dwellings. The purchaser, knowing the need 
 for high decay resistance, is prepared to pay the cost of getting it. 
 Appreciable quantities of sash treated with watei borne preservatives 
 have been installed in dye houses, textile mills, paper mills, and the 
 like. In at least one case the sash and frames in a locomotive round 
 house were creosoted and left uxpainted. The result was considered 
 much more satisfactory than that obtained with untreated wood or metal 
 sash* 
 
 Specifications for Sash Treatment 
 
 Standard specifications Covering acceptable preservatives and 
 methods of treatment for sash and similar products are highly desirable 
 in order to avoid the confusion and doubt that are certain to arise in 
 the minds of architects and consumers because of conflicting statements 
 made by promoters and users of various sash treatments. Attempts are 
 now being made by organized sash manufacturers to bring this about. The 
 early adoption of good specifications that can be used by both producers 
 and consumers will be very helpful. 
 
 Clean Treatment of Other Products 
 
 Although the foregoing discussion has been limited mainly to 
 sash and frames it has general application to other products, including 
 shutters, flooring, finish lumber, garage and other outside doors, auto- 
 mobile body parts, refrigerator parts, partitions, office equipment, and 
 furniture, when they are to be used under conditions that require re- 
 sistance to decay or insects. Under the conditions that ordinarily pre- 
 vail in buildings throughout most of the United States no preservative 
 treatment is required for floors, partitions, interior finish, lumber, 
 or furniture, but it may be required in special cases or for use in warm 
 humid climates, when it is known in advance that service conditions will 
 be severe. 
 
 Moderate resistance to termites, as well as decay resistance, 
 can be obtained by the use of heart redwood or heart cypress in products 
 for which these woods are suitable. For other products or for other 
 American woods, or where maximum termite and decay resistance is required 
 preservatives should be used* 
 
 With wooden refrigerator parts, and with any other wood that 
 is to be used in close proximity to food, especial consideration must be 
 given to avoiding odor and contamination. Toxic chemicals that endanger" 
 health must be avoided in treating wood that is handled frequently, or 
 that will be used in interiors of buildings. 
 
 R919 -9- 
 
Results to be Expected 
 
 It is not possible to predict with certainty the number of years 
 cf additional service that can reasonably be expected from treatment of 
 sash and similar products- The conditions of service have much to do with 
 the result. Thorough impregnation with coal tar creosote under pressure, 
 resulting in absorptions cf 12 pounds of creosote or more per cubic foot 
 of wood should give complete decay protection to sash, doors, and similar 
 products throughout their mechanical life or the useful life of the 
 building in which they are installed. Creosote treatment, however, is 
 seldom acceptable for such products. 
 
 Thorough pressure treatment with reputable water borne pre- 
 servatives should give about the same results as creosoting in situations 
 where the wood may be damp but will not be exposed to the leaching effect 
 of constant or frequent contact with free water. Where service conditions 
 favor leaching water borne preservatives will be less effective than 
 creosote. 
 
 The special sash preservatives containing not less than 5 per- 
 cent of a stable and suitable toxicant have not been in use long enough 
 to have shown by their performance in actual service just how they com- 
 pare in effectiveness with creosote and water borne preservatives. Labo- 
 ratory tests and such limited service tests as are available, however, 
 indicate that they should give satisfactory results. It is reasonable, 
 on the basis of the information thus far available, to expect these pre- 
 servatives to give satisfactory protection when they are thoroughly im- 
 pregnated into wood in substantial quantities. 
 
 Most sash and similar products are not used under the most 
 severe service conditions, and consequently they do not require the heavy 
 treatment necessary for outdoor structural timbers. Simple immersion 
 for 3 minutes or longer in special sash preservatives of high quality 
 is probably sufficient to prevent decay in sash in ordinary homes and 
 office buildings, if the treated wood is not trimmed off in subsequent 
 fitting operations. Where conditions are very favoraole to rapid decay 
 or stain, more thorough impregnation is considered necessary for adequate 
 protection. 
 
 Dipping for a few seconds in any preservative gives only a 
 slight degree of protection and is not considered adequate for general 
 
 use. 
 
 -10- 
 
{■TKESSly 0F FLORIDA 
 
 3 1262 08927 4301