CHEMICAL UTILIZATION OF WOOD: 

Its Opportunities and Obstacles 

December 1945 

No. R1601 

UNITED STATES DEPARTMENT OF AGRICULTURE 

FOREST SERVICE 

FOREST PRODUCTS LABORATORY 

Madison, Wisconsin 

In Cooperation with the University of Wisconsin 
--- 

1 

CHEMICAL UTILIZATION OF WOOD: ITS OPPORTUNITIES AND OBSTACLES 

BY 

ALFRED J. STAMM, Chief 

Division of Derived Products 

Wood Waste 

It is hardly necessary to point out to foresters the huge amount of 

wood that is wasted each year in the United States. Even Mr. Average 

Citizen is becoming mindful of the vast waste. 

ratory receives letters regularly from those who are anxious to do something

This 

The Forest Products Laboconstructive in utilizing wood waste but who need help in doing so. 

situation has been brought to the attention of Congress. As a result, they 

have earmarked a small increase in the Forest Products Laboratory appropriation for this fiscal year to be used in studying the chemical utilization 

of wood. It is hoped that this amount will be further increased in future 

years as the chemical approach to this important problem shows much promise 

of making important contribution to the eventual solution of the waste 

problem on an economic basis. 

Although the Laboratory's approach to the problem is from the Chemical standpoint, it will take more than the chemist to solve it adequately. 

Even if the chemist had all the chemical facts regarding a potential utilization process, there is still the necessity of determining its economic 

and mechanical feasibility. Economical harvesting and transporting of wood 

waste so that it can be delivered cheaply for chemical use seems to be the 

biggest obstacle confronting the chemical utilization of wood. This phase 

of the over-all problem is the one in which foresters and engineers can 

make their biggest contribution. Those who are anxious to contribute to 

the solution of the waste-utilization problem can well focus attention on 

harvesting and transportation of woods waste in small log, cordwood, chip, 

or sawdust form. 

Chemical Utilization 

The chemical utilization of wood may be divided into several types 

of processes; (1) pulping, (2) extraction, (3) hydrolysis (converting 

1Presented before the Southeastern Section, Society of American Foresters, 

Auburn, Alabama, October 26, 1945, 

Report No. R1601 -1-
carbohydrates to sugars), (4) destructive distillation, (5) reactions with 

various chemicals such as hydrogen and chlorine, and (6) chemical treatments to Improve the properties of wood and make possible the utilization 

of inferior species for structural use. 

Pulping 

Pulping processes are the oldest and best known of the processes for 

chemical utilization of wood, Experience has shown, however, that pulping 

cannot be done profitably on a small scale. Large-scale and costly equipment is necessary for efficient and economical operation. 

Attempts have been made to operate pulp mills on inferior quality 

wood and waste. In a few instaces these attempts have been successful. 

A notable example is the pulping of chestnut chips that have been extracted 

for tannin, In general, operators who have tried using low-grade wood have 

abandoned its use and turned to high-quality material in order to increase 

the returns from their investments. As quality material becomes less available, these operators can and will return to the use of the less desirable 

woods, 

Development of a simple means of barking hardwoods at a11 seasons 

as well as small crooked softwood logs will help materially in getting the 

pulp mills to use more of the presently unpopular species and lower-grade 

woods. Softwood mill waste is now being utilized by some pulp mills operating in conjunction with a sawmill, All logs going to the mill are prebarked, The slabs and, for some forms of paper, even the sawdust are being 

used for pulping. 

Work at the Forest Products Laboratory on diversification of pulping 

species, notably the pulping of southern resinous softwoods and the semichemical pulping of hardwoods, has gone a long way toward making all available species suitable for pulping, The inclusion of some hardwoods in 

southern pine pulping operations has been shown to be practical and highly 

advantageous from a silvicultural and economic standpoint, Foresters can 

aid in getting various mill operators to follow such practice. 

Efforts are being made to utilize more completely pulp-mill waste 

liquors. These liquors contain soluble lignin, hemicelluloses, and wood 

extractives which have considerable potential chemical value. In the 

sulfate pulping of Southern yellow pine, turpentine and tall oil are now 

being recovered to a limited extent. Yield of tall oil as high as 200 

pounds per ton of pulp are obtained, The tall oil is finding use in drying 

oils and soaps, Further purification and fractionation should increase its 

value and uses. 

Sulfite waste liquor is being used to some extent as a dust settler 

for roads. Lignin is finding use as a dispersing agent for cement in the 

making of concrete; it is being incorporated in the negative plate paste of 

electrical storage batteries; and it is used in making vanillin, the active 

constituent in vanilla extract, 

Report No. R1601 -2-
Cooperative research between the Forest Products Laboratory and a 

Canadian mill has demonstrated the possibility of using soda-mill lignin 

in laminated plastics. Soda-mill lignin is the simplest to isolate and has 

the best plastic properties of the various forms of lignin waste. It 

be incorporated with the pulp in a beater to form a laminating sheet which 

requires no auxiliary resin to produce a dense plastic material with good 

properties. The Forest Products Laboratory has also shown that soda-mill 

lignin can be used as a phenolic-resin diluent. The lignin is dissolved in 

a laminating resin solution and can be applied to paper or fabric. It can 

replace 50 percent of the phenolic-resin ordinarily used without Significantly affecting the properties of the resulting laminate. 

The hemicellulose portion of pulping-waste liquor has received less 

attention than the lignin even though it is present in the liquor in at 

least equal amount. The hemicelluloses are converted almost entirely to 

sugars in the sulfite process. In the soda process they are much less degraded and can be isolated as starchlike products. 

The sugars from the sulfite process are, to some extent, being fermented to ethyl alcohol and used for growing yeast, as will be described 

later. Ethyl alcohol is produced only from the hexose sugars and not from 

the pentose sugars. The pentose sugars can, however, be used for growing 

of yeast or fermenting to other poducts. 

The chemistry and possible uses of hemicelluloses are being studied 

by the Forest Products Laboratory, where it has been shown that hemicelluloses can be isolated from wood in a practically undegraded form by a new 

potential pulping process. Practically all the carbohydrate constituents 

of wood (holocellulose) are isolated as a single solid fraction by subjecting wood chips to a semichemical pulping, followed by chlorination and 

mild alkali extraction. Various hemicellulose fractions can be extracted 

from the holocellulose by progressively stronger solvents, leaving a residual pulp that is considerably higher in alpha cellulose (high-molecularweight undegraded cellulose) than normal pulps, and which shows promise of 

finding use in cellulose derivatives, Such a pulping method would not only 

give extra high yields of high-quality pulp, but would also make possible 

the isolation of valuable hemicellulose by products. 

Extraction. 

Extraction processes can be profitably applied to only a relatively 

few species, such as the turpentine and rosin extraction of southern pine 

stumps and tannin extraction of chestnut and hemlock. These processes 

utilize only a small portion of the wood. The problem of utilizing the 

rest of the wood profitably still exists, This has in some instances been 

accomplished by pulping the extracted chips, For this use the wood should 

be barked prior to chipping and extraction, Extraction of wood for chemical~ on a scale too small to use the spent chips for pulping may eventually 

become profitable if other means of utilizing the residual wood substance 

are found, Expanding the wood extraction industries thus depends to a large 

extent upon finding uses for the extracted chips. 

Report No. R1601 -3-
Hydrolysis for Production of Alcohol 

Next to pulping, wood hydrolysis has received major attention as a 

chemical utilization process at the Forest Products Laboratory during the 

last few years. Ethyl alcohol (grain alcohol) can be made from wood waste 

by hydrolyzing the carbohydrate portion of the wood to sugar, followed by 

fermentation of the sugar to alcohol. The general principles of this conversion have been known for years. At the time of World War I and shortly 

thereafter a process known as the American process using Southern yellow 

pine woods waste, was in operation in two plants in the United States; one 

at Georgetown, South Carolina, and the other at Fullerton, Louisiana. The 

process, which consisted of a single rapid digestion of the wood with 

dilute acid followed by extraction of the sugar and hatch fermentation Of 

the sugar liquors, produced about 26 gallons of 95 percent alcohol per ton 

of dry wood. Each plant produced about 2,500 gallons per day. Operation

of these plants was finally diecontinued because of the lack of adequate 

woods waste near the plants and the substantial lowering of the price of 

blackstrap molasses (to 5 cents a gallon) from which alcohol could be 

produced more cheaply. 

About 1928 a multiple-cycle dilute-acid-hydrolysis process, known as 

the Scholler process, was developed in Germany. Yields of about 45 gallons 

per ton were obtained from hardwoods and 53 gallons per ton from softwoods. 

Cooking times, however, ranged from 16 to 20 hours. During World War II 

pilot-plant studies were intensively undertaken by the Forest Products Laboratory, first to duplicate and then to improve on the German process. This 

work has resulted in what is called the Madison wood-sugar process. Cooking

liquor is continuously pumped through a bed of wood waste for 2-1/2 to 3 

hours under properly controlled conditions, followed by a continuous fermentation. Yields of 55 to 65 gallons per ton of bark-free softwood waste have 

been obtained. The improved yield, together with the reduction in cooking

time to as low as one-sixth to one-eighth of that for the Scholler process, 

gives the process a better commercial outlook, A Government-sponsored plant designed to produce 5 to 6 million gallons of alcohol a year from about 380 

tons of sawmill wood waste per day by this method is under construction at 

Springfield, Oregon. 

According to the Forest Products Laboratory experiments, wood with 

bark contents as high as 50 percent can be handled but with a significant 

drop in yield. Hardwoods can be used instead of softwood. Although the 

alcohol yield drops to about 45 gallons per ton, larger amounts of valuable 

byproduct wood alcohol and furfural can be recovered to offset the loss in 

ethyl alcohol yield. The Laboratory has also shown that yeast can be grown 

on the still bottoms, after recovery of the alcohol, to produce about 200 

pounds of fodder-yeast byproduct per ton of dry wood. 

From each ton of wood processed there is about 650 pounds of residual 

lignin. As yet there has not been found a profitable use for this residue. 

Present plans are to use it as a fuel in the plant boilers. This lignin is 

in a highly insoluble form and is not suitable according to present informtion for use in plastics in the same way that lignin residue from soda pulp 

Report No. R1601 -4-
can be used. Work is under way at the Laboratory in the search for profitable uses for this residue. 

This new alcohol process has created a great deal of public interest. 

In fact, almost everyone with a little sawdust pile wants to make alcohol. 

It is thus important to look at some of the economic aspects of the problem. 

Consider wood waste in a hogged form delivered at the chemical plant 

to be worth $2.00 per ton on a dry-weight, bark-free basis. Moisture and 

some bark are acceptable but a processor will not pay for them. The wood 

cost per gallon of 95 percent alcohol would then be about 4 cents and the 

chemical cost would be about 6 cents. On the basis of a plant processing 

60 tons of dry, bark-free waste per day (approximately 200 tons with bark 

and moisture), labor would cost about 8 cents per gallon of alcohol and 

plant Investment and upkeep 16 cents a gallon. The production cost of alcohol would thus be 34 cents per gallon, a figure within reason. In a larger 

plant labor charges may be as low as 5 cents per gallon. On the basis of a 

10-ton-a-dayplant the total labor required would be almost the same as for 

a 60-ton plant, which, on the smaller daily output, would amount to perhaps 

45 cents per gallon. A 10-ton-a-day plant might cost two-thirds as much 

to build as a 60-ton-a-dayplant, bringing the plant investment and upkeep 

cost to 64 cents per gallon of alcohol. The production cost of alcohol 

from the 10-ton plant would thus be 1.19 per gallon. It is evident from 

these figures that the manufacture of alcohol from wood is necessarily a 

large-scale operation. 

There is the possibility of hauling wood waste from several mills to 

a central chemical plant. By present handling methods it appears that wood 

waste cannot be profitably hauled much more than about 10 miles. There is 

the radius of haul tentatively chosen as economical for the Springfield 

wood-sugar plant. 

Comparative cost of alcohol produced by other methods has a direct 

'bearing on the commercial application of the process. Alcohol is being 

produced in the State of Washington and in Canada from sulfite-pulp waste 

liquor. Plant costs are about the same as estimated for the Madison woodsugar process. No hydrolysis step is involved but, because of the more 

dilute liquor, larger volumes have to be handled. Production costs on a 

large-plant basis would probably be about 25 cents per gallon, which is 

somewhat less than the estimated cost of production by the Madison woodsugar process. Alcohol was produced from blackstrap molasses at about 20 

cents per gallon when the cost of molasses was 5 cents per gallon at the 

plant, At the present molasses price of 18 to 20 cents per gallon, it 

would cost 50 to 56 cents a gallon to produce alcohol from this source. 

Ethyl alcohol made from grain, at present grain prices, ranges in production 

cost from 85 cents to $1.50 per gallon, depending on the size and efficiency 

of the plant. Ethyl alcohol can be produced from petroleum at a somewhat 

lower cost than by the Madison wood-sugar process. It is hard to say, however, whether the petroleum companies will turn to making alcohol as long 

as they can make more profitable products. It thus appears that the future 

of making ethyl alcohol from wood waste depends upon the cost of blackstrap 

molasses not falling below 10 cents per gallon and the petroleum industry 

Report No. R1601 -5-
not going into the manufacture of alcohol. Finding a profitable use for the 

residual lignin will also materially help the production of ethyl alcohol 

from wood. If all the sulfite liquor from pulp mills were fermented alcohol 

production from this source would be about 30 million gallons of alcohol per 

year, which is about 3 percent of present annual production, Some mills are 

too small to produce alcohol economically. 

Other Fermentation Products 

When wood sugars are fermented with the use of cultures and nutrients 

other than those used in producing ethyl alcohol, such products as acetone, 

butanol, 2,3-butylene glycol, and lactic acid can be produced. These find 

use as solvents and as raw materials for making synthetic rubber and plastics. As yet, available data on these processes are insufficient to indicate how they should be carried out commercially and what the cost of production will be. 

Fodder yeast can also be grown on the total sugars as well as on the 

still bottoms. The extent to which this vitamin-containing food can be 

used profitably for feeding is still unknown, Cattle can assimilate urea, 

the nutrient ordinarily used in growing fodder yeast, and convert it into 

protein. It still remains to be proven whether fodder yeast is a better 

food for cattle than urea and to what extent it may replace other natural 

protein-containing foods. The quantity of fodder yeast made in this country 

up to the present time has been insufficient to make adequate feeding tests. 

This situation, however, should change soon. 

Hydrolysis for Production of Plastics 

and Board Materials 

Pioneer experiments by the Forest, Products Laboratory showed that 

lignin, in a sense Nature's cementing material between the cellulose fibers, 

can be freed from the cellulose by a mild acid hydrolysis and be subsequently used as a semiplastic to bond the structure together again. Besides 

breaking the cellulose-lignin bond, the mild hydrolysis converts the hemicelluloses to sugars, while the stable cellulose remains with the lignin to 

serve as a plastic reinforcing material, The removed sugars can be either 

fermented or used for the growing of yeast. The residue is dried and then 

ground to a powder. Although this hydrolyzed residue does have some plastic 

Properties, it does not make a good plastic when used alone, due to the 

extremely high temperature necessary to cause the lignin to flow even moderately and the relatively low water resistance of the product. For this 

reason it is preferably used in conjunction with other plastics such as 

phenol formaldehyde, which improves both the flow and the water resistance. 

Under these conditions a plastic quite similar in appearance, water resistance, and electrical properties to common black phenol-formaldehyde plastics 

can be made using 75 percent of hydrolyzed wood and 25 percent of phenolic

resin. This can be contrasted with the 50 percent of wood flour and 50 

percent of phenolic resin used in making the ordinary phenol-formaldehyde 

Report No. R1601 -6-
molded products. The strength properties, notably toughness, are slightly 

lower than for the normal phenol-formaldehyde molded products, mold flow is 

also inferior, but acid-resistance properties are better. 

a commercially developed modification of the Forest Products Laboratory acid-hydrolysis process, in which the wood is hydrolyzed with an 

alkaline medium which becomes slightly acid at the end of the cook, gives a 

similar molding powder with superior strength properties to those of the 

acid-hydrolyzed product. This material, when used with only 25 percent of 

phenolic resin, still lacks the rapid and more extensive flow of the ordinary phenol-formaldehyde molded products, which results from the greater 

content of phenolic resin. Although the addition of more resin improves 

the flow, it reduces the price advantage. It is this lack of flow that has 

held back the commercial use of hydrolyzed-wood plastics. In large objects 

with limited need for flow, hydrolyzed-wood plastics may, however, be used 

to advantage because of the lower cost. On the basis of the phenolic resin 

costing 20 cents a pound, wood flour costing 2 cents per pound, and hydrolyzed wood costing 4 cents a pound, the raw material for the hydrolyzedwood plastic would cast 8 cents per pound, in contrast to 11 cents per 

pound for the present material. 

Research is under way at the Forest Products Laboratory to put the 

lignin into a more plastic form so as to improve its flow characteristics 

and also avoid the embrittling effect on the cellulose caused by the hydrolytic methods that have been used to date, 

The hydrolyzed-wood plastic requires pressures of 3,000 to 4,000 

pounds per square inch at elevated temperatures for molding similar to the 

present molding powders. This necessitates expensive presses and molds. 

There is a crying need for molding compositions that can be cold formed in 

a simple hand press, perhaps followed by a simple baking. This problem, 

too, is being attacked at the Forest Products Laboratory. The chief difficulty to date has been that the simpler, cheaper compositions which are 

readily hand molded all exhibit considerable shrinkage on baking. 

Unfortunately, none of the molding compositions show promise of 

utilizing very large quantities of wood waste. For example, if all of the 

present phenol-formaldehyde molded products were to be replaced by the 

hydrolyzed-wood plastics, three moderate-sized lumber mills could furnish 

all the raw material needed in the country. As board materials show promise 

of larger volume consumption, considerable attention has been focused at 

the Forest Products Laboratory in making such materials. 

The hydrolyzed-wood molding powders are not suitable for making 

board materials with adequate strength properties, notably toughness. The 

strength properties can be greatly improved by having the cellulose reinforcing material present in longer-fibered form. This can be accomplished 

by using hardwood chips in place of sawdust and abrading the washed hydrolyzed chips while still wet to a pulp rather than grinding to a powder after 

drying. This pulp can be made into paper on a paper machine. After incorporating 10 to 15 percent of phenolic resin, these sheets can be pressed at 

elevated temperatures and a pressure of about 2,000 pounds per square inch 

Report No. R1601 -7-
into a high-density board with quite good strength properties and water 

resistance. The board cannot be nailed but can be drilled. This, together 

with its high density and molding cost, do not make it attractive for general 

housing applications. It, however, should be suitable for electrical paneling and for such purposes as shower-bath walls. 

More recently pulp boards have been made by the Forest Products Laboratory from the hydrolyzed chip fiber by forming thick pulp mats that are 

pressed wet under a pressure of 100 pounds per square inch or less without 

the addition of any phenolic resin. These boards have quite good properties 

comparable to those of untempered commercial hardboards. The boards which 

have a specific gravity of about 1.0 can be nailed. They can be made from 

softwoods as well as hardwoods, but the strength properties and water resistance of the softwood product are somewhat inferior. 

Although these and other similar hardboards show promise for use as a sheathing material for houses and in other ways that wood is used, they 

are far from being synthetic lumber. Their use in housing will, undoubtedly, 

expand, Some new producers will undoubtedly succeed. If all who have contemplated production of these board materials actually go into production, 

however, a state of overproduction will be inevitable. 

Destructive Distillation 

Prior to the development and the industrialization of the present 

process for making synthetic wood alcohol, wood distillation was a profitable industry. only a few plants have survived this development. During 

the war period, however, considerable interest in distillation has been 

revived, largely because of the increased demand for charcoal. No new extensive plants have been built but some charcoal manufacture without recovery 

Of volatiles has been renewed. There is still, however, the possibility Of 

reviving the wood-distillation industry by introducing new principles Of 

distillation that will result in other than the conventional products. Such 

distillation principles can be applied to lignin residues from which it has 

been shown that valuable phenolic compounds can be obtained. The Forest 

Products Laboratory is again launching on a destructive-distillation research 

program after an inactive period of about 20 years, as it is felt that the 

introduction of new techniques may revive an old industry that under the old 

methods does not have a promising postwar outlook. 

Hydrogenation of Wood 

It has been shown from pioneer research at the Forest Products Laboratory that lignin dissolved in organic solvents or suspended in water can 

be made to react with hydrogen gas at elevated temperatures and pressures 

in the presence of various metallic catalysts. Among the products of the 

reaction are several brand new cyclic alcohols that had never been previously 

described in the literature. These show promise as plastic solvents, antiknock agents for motor fuel, and toxic agents. By varying the hydrogenation 

Report No, R1601 -8-
conditions, phenolic compounds which may find use in plastics and complex 

neutral oils, together with a plastic-like residue, are obtained. 

Wood waste or chips can also be hydrogenated in aqueous suspension 

to produce soluble lignin decomposition compounds and a cellulose pulp 

residue. This is a possible new pulping process that will be studied 

further by the Forest Products Laboratory, Under more severe hydrogenation 

conditions the cellulose can be converted to glycerine and sugars. In this 

case the entire wood is converted to liquid products. 

All these findings are too new to predict their future application. 

Most of the data have been obtained in small bombs and in continuous hydrogenation equipment designed for other hydrogenation reactions. continuous 

hydrogenation equipment is being built at the Forest Products Laboratory

for continuing this work, 

Modified Woods 

The modification of wood by chemical treatments and by compression 

has excited a great deal of interest during the war period as a result of 

the publicity which the materials have received. These modified woods 

should not be thought of as improved forms of general utility lumber, as 

has often been inferred, but specialty materials for uses where their 

special properties are needed. 

Impreg 

Wood treated with phenolic-resin forming chemicals according to the 

Forest Products Laboratory method in which the chemicals enter and bond to 

the cell-wall structure, followed by drying and curing of the resin within 

the structure, is known as impreg. When resin is thus made an intimate 

part of the wood the tendency of the wood to swell and shrink is permanently 

reduced. Phenolic-resin forming systems have proven to be the most effective in dimensionally stabilizing wood. Reductions in the equilibrium 

swelling and shrinking to 30 percent of normal are possible with phenolic 

resins. Urea resins, which have been highly publicized of late for this 

purpose, reduce the equilibrium swelling by only half as much. 

stabilization of wood by a resin treatment differs from preservative 

and fire-retardant treatments in that it must be much more complete, The 

resin must be uniformly distributed throughout the entire cell-wall structure to be fully effective. For this reason the treating of lumber and the 

treating of freshly felled logs has not met with the success that some 

investigators have claimed. The Forest Products Laboratory has found that 

veneer of practically any species and many species of solid wood in lengths 

up to a foot or two can be adequately treated. Practically none of the 

woods can be properly treated in lumber lengths. Even if lumber could be 

adequately treated, the increase in cost would make the material prohibitively expensive for the majority of proposed uses. It is nevertheless 

Report No. R1601 -9-
felt that the resin treatment of veneer for facing of plywood and for various specialties will find considerable use. 

The face checking of plywood can be practically eliminated merely by 

facing normal plywood with phenolic-resin-treated faces. 

The treatment also imparts to the panels considerable resistance 

against decay, termite, and marine-borer attack. A panel consisting of two 

resin-treated face plies with a single untreated core ply was inserted in 

the ground for 1 year in a field in Mississippi where termite action is 

severe. The termites tried the faces but found them not to their liking. 

Like good soldiers who have failed in a frontal attack, they tried a flank 

attack and, finding the core just what they wanted, proceeded to clean it 

out, Similar material that has had the edges protected with a preservative 

treatment and material with all the plies treated is, in some instances, 

sound after 5 years. 

The resin treatment further cuts down the passage of water vapor 

through the panels to a marked extent, greatly increases the electrical 

resistance and the resistance to most chemicals with the exception of 

strong alkalies. Contrary to many of the publicity claims, resin treatment 

has a negligible effect in improving fire resistance. Fire-resistant salts, 

however, may be incorporated into the wood together with the treating resin 

and fixed in the structure by the treating resin to give quite good fireretardant properties. 

Only a few of the strength properties of wood are significantly increased by a resin treatment and the toughness is significantly decreased, 

which is contrary to much of the publicity on resin-treated wood. The only 

properties that are significantly increased are hardness, compressive 

strength, and abrasion resistance, and these are increased to a greater 

extent than the weight only at high resin contents. 

Impreg was manufactured during the war only for military uses, one of 

which was for housings for electrical control equipment, in which the improved electrical properties are taken advantage of and another in an as yet 

unreleased use in which the improved abrasion resistance is utilized. 

Impreg shows the greatest promise for postwar use as resin-treated faces for 

ordinary plywood. Such panels might be used as house, trailer, and boxcar 

siding, flooring, and paneling. It still has to be proven, however, that 

the improved properties warrant the increased cost. 

Compreg 

Compreg is the name given by the Forest Products Laboratory to their 

stable form of resin-treated compressed wood. Its dimensional stability, 

resistance to organisms, chemicals, and flow of electricity are practically 

the same as for impreg. Most of the strength properties are increased about 

in proportion to the compression. It is tougher than impreg but not quite 

SO tough as the original wood, 

Report No. R1601. -10-
Due to the plasticizing action of the resin-forming chemicals on wood 

at temperatures used in hot pressing, the treated wood can be appreciably 

compressed under a pressure which scarcely compresses an untreated control. 

Because of this plasticizing action of the resin-forming chemicals on wood 

it is possible to make a combination of resin-treated compressed faces on an 

untreated uncompressed core in a single assembly and compression operation. 

It is felt that in this form compreg will find most of its postwar uses. 

When compreg is compressed to a specific gravity of about 0.9 to 1.4, 

it assumes a glossy finish which persists throughout the structure. A cut 

surface can be sanded and buffed to a high degree of finish without the use 

of applied coatings. This is a feature of compreg which would make it 

desirable for use in furniture and flooring. Panels with a yellow-poplar 

compreg face, yellow-poplar impreg back and a Douglas-fir plywood core have 

been made for a flooring service test that is now under way in one of the 

Forest Products Laboratory offices. 

Compreg, largely in the form of thick, highly compressed panels, has 

been manufactured during the war by seven companies for war use, chiefly in 

the manufacture of propellers, Compreg has also been used to sone extent 

for various connector and bearing plates, aerial antenna masts, and tooling 

jigs. Solid compreg shows promise for postwar use in pulley and gear 

wheels, bearings, tooling jigs; shuttles, bobbins, and picker sticks for 

looms; high-strength electrical insulators; knife handles; and various decorative novelties. Compreg has better strength properties than fabricreinforced plastics and it should be appreciably cheaper due to the fact 

that veneer is cheaper than fabric and about half as much resin is used in 

making compreg as is used in the fabric-reinforced plastics. Compreg may 

thus replace these plastics in a number of uses. 

Staypak 

Resin-treated wood in both the uncompressed and compressed forms is, 

unfortunately, more brittle than the original wood. To meet the demand for 

a tougher compressed product than compreg, a compressed wood containing no 

resin was developed by the Forest Products Laboratory. It will not lose 

its compression under swelling conditions as will ordinary compressed wood. 

This material, named staypak, is made by modifying the compressing conditions so as to cause the lignin cementing material between the cellulose 

fibers to flow sufficiently to eliminate the internal stresses. Staypak is 

not so water-resistant as compreg, but it is twice as tough and has higher 

tensile and flexural properties. The natural finish of stay-pak is almost 

as good as that of compreg, Under weathering conditions, however, it is 

definitely inferior to compreg. For outdoor use staypak should have a good 

synthetic resin varnish or paint finish, Staypak can be used in the same 

way as compreg where extremely high water resistance is not needed, It 

shows promise for use in propellers, tool handles, forming dies and connector plate6 where high impact strength is needed. 

Report No. R1601 -11-
Staybwood 

The cheapest and simplest method of imparting dimensional stability 

to wood thus far found is to heat the wood under conditions that just avoid 

charring. This can be done with a minimum loss in strength properties by 

the Forest Products Laboratory method of heating under molten metal for a 

few minutes. The wood becomes dark brown in color, loses about half of its 

original toughness, together with moderate losses in other strength properties. Equilibrium swelling and shrinking can be reduced to 60 percent of 

normal and an appreciable decay resistance is imparted to the wood by this 

treatment. Staybwood may find some use in places where dimensional stability and moderate decay resistance are more important than strength. 

Conclusions 

Although a great deal has been accomplished in developing means of 

chemically utilizing wood and in making modified woods, no universally 

successful process of utilizing the vast amount of inferior or waste wood 

has been developed. Individual operators, however, may be successful in 

using any of the processes discussed. Their success will largely depend 

upon making careful surveys of the source of wood supply, markets, and 

economical size of the prospective plant before venturing into any extensive 

operations. 

Although the modified-wood field is primarily based on using highquality wood chiefly in the form of veneer, there is the possibility of 

some manufacture based on the use of short dimension stock that is classed 

as waste because of size rather than quality. Compreg knife and other 

handles, knobs, and various decorative novelties can all be made to advantage from short lengths of solid wood rather than from veneer, The increased 

value of the product would make possible a more scrupulous selection of wood 

than would be possible for similar products made from untreated wood. 

Further research on chemical utilization and modification of wood will 

undoubtedly expand the present possibilities of waste utilization, but the 

chemist needs the help of the forester in working out the problem of delivering the waste cheaply in large quantities to the processing plants. 

Report No. R1601 -12-