Aug. 9, 2009, 01:05 PM
What and When
1. ORIGIN.-Though its proper care depends largely upon a proper knowledge and understanding of its origin and the processes of its manufacture, it is perhaps unnecessary to give a definition of leather. Suffice it to say that leather originally was the skin of an animal, and that through a chemical process called "tanning" this skin is made into leather. It is not so generally known, however, that while the antiquity of the processes of tanning are unknown, the industry was practiced in the remote ages by the Chinese. It was practiced as early as 900 B.C. by the Egyptians (as evidenced by pieces of eather now in the British Museum taken from a mummy case of that age). It was practiced at the beginning of the Christian Era by the Romans, who accidentally discovered the tanning processes and grew to be much skilled in the preparation and finishing of leather. Strange does it seem, therefore, that despite the almost universal use of skins by savages, so many aboriginal peoples remained, almost up to the present time, ignorant of the art of tanning. The answer probably lies partly in the fact that the chemical processes are more or less complicated, depending upon the method of tanning used, and partly in the fact that proper chemicals were either unknown or unavailable.
2. TANNING.-In its original raw state an animal's skin is made up of three layers, the outer, or hairy, which has no blood vessels; the middle, which is the true skin, made up of gelatinous fibers; and the inner, a fatty layer, in which are imbedded the perspiratory and sebaceous glands. All processes of tanning have generally for their first object the reduction of the skin to the middle layer, or true skin. The inner, fatty layer and the outer, hairy layer are removed by steps called "cleaning" and "depilation."
The cleaning of the hides is accomplished by soaking them in frequently changed water until they are soft, which may take two to three weeks, after which all adherent fatty tissue is scraped from the inside. Depilation is accomplished in two ways, - by sweating and by liming. In the sweating process, for the production of what is called "raw" leather, the hides are suspended in pits at a uniform temperature (64.50 F.) and in a moist atmosphere until they undergo a partial decomposition, the ammonia produced saponifying the fats around the roots of the hairs, after which the hairs may be scraped off. In the liming process, for the production of what is called "finished" leather, the softened hides are soaked in lime water until the hair may be removed, the lime acting as a saponifier, after which the excess lime must be removed from the hides by an acid (sulphuric) which, in turn, "plumps" the fibers, materially increasing the hide's thickness. The hides must then be treated with a putrefactive or fermenting element called "bate" (such as sour bran), which softens the hides and abates the "plumpness". After these processes have been accomplished, the hides are ready for tanning.
In this country there are two common methods of tanning called, respectively, the vegetable (or tannic acid) and mineral methods. The vegetable method, in which the tannin generally comes from oak or hemlock bark, produces what is commonly conceded to be the best leather for many purposes, especially heavy leather, but takes a long time and is therefore relatively expensive. Generally, in this process, the bark is thoroughly ground, then leached to extract the tanning principle from it. The hides are first placed in a weak solution of this tannic acid and then transferred successively to vats where the liquor is stronger until the processes are complete. Depending on many conditions, the complete process may require from two to fifteen months.
The chrome tanning process, which is the principal process of the mineral tanning method, was discovered by an American, and first used about 1890. It is a quick, relatively cheap method, requiring much less time to accomplish tha ii the vegetable method. Used mainly for tanning lighter leather, it produces leather with great water repellant and heat resisting properties, generally of great tensile strength, but much more difficult to dye than that tanned by the tannic acid method. Briefly, it consists of treating the hides with a weak solution of dichromate of potash to which sufficient hydrochloric acid has been added to liberate chromic acid, which is the tanning principle. After the skins have taken up a bright yellow color throughout their texture, they are drained and transferred to a bath 6f hyposulphite of soda to which hydrochloric acid again is added. This liberates sulphurous acid, which reduces the excess of chromic acid to green chromic oxide, which, in effect, coats each fiber with a casing that preserves it, and gives the resulting leather a characteristic pale bluish-green color. Upon removal from the bath, the leather must, because of its water repellant properties, be dyed while still moist by applying the color dye desired. If allowed to dry before dyeing, it can never again be sufficiently wetted to dye properly. Even then the dye does not penetrate the surface greatly, which is shown by the finish of boot uppers wearing where the stirrup strap crosses the shin, and prevents its being ever redyed properly.
There are also for different animal skins, such as chamois, sheep, pig, calf, etc., different tanning processes, such as oil tanning, smoke tanning, Indian tanning, etc., followed in this and different countries, all of which, however, are directed generally to the same end, i.e., the conversion of the gelatinous tissues of the skin into the non-putrescible substance we know as leather. (See section II and V, TM 10-226.)
3. CLASSIFICATION.-During the tanning processes if the hides have not been "bated" (steeped in a mixture to soften and reduce the swelling of the fibers), the resulting product is called "raw" leather; if bated during the tanning process, the resulting product is called "finished" leather. In order to finish raw leather it is necessary to scour it and compress it. by a strike pin and roller. If the leather is stuffed with oils to increase its resistance to water and to make it more flexible, it is then called "dressed". It may then be dyed or stained, after which it may be grained by rolling, if desired. Nearly all items of manufactured leather equipment (harness, saddles, bridles, etc.) are made from dressed leather.Agents for Cleaning and Preserving Leather
4. GENERAL-There are so many agents used for cleaning and preserving leather, both raw chemicals and mixtures of them sold under trade names, that it would be impracticable to list all of them here. In an effort to give some idea, however, of the composition and properties of a few of the better known and more generally used ones, the tabulation indicated in succeeding paragraphs has been made.
5. CLEANING AGENTS.-Cleaning agents are as follows:
a. Soap -The purpose of all soaps is to clean, which they do by exhibiting, in their lathered state, an attraction for the dirt particles exceeding the attraction of the leather for them. Formed generally by the union of a fatty acid with a base (compound of a fat with an alkali), soaps should not be caustic if they are to be used on leather; they should also, to be classed as "saddle soaps", possess some fixed oils that assist in preserving the leather after the lather itself has cleaned it. If properly used, the saddle soaps will clean the leather and at the same time, at least to an extent, oil it. A proper method for day-to-day cleaning and preserving is to work up a light lather with saddle soap and sponge, going lightly over both the inside and outside surfaces of the leather and working the lather into it, after which any excess of the lather may be removed with either an almost dry sponge or with a light flannel cloth. It must be emphasized that in day-to-day cleaning and preserving with soap as little water as possible should be used in working up the lather, so that the lather itself will be "light and dry". If it is desired periodically, to thoroughly clean with soap, as prior to oiling, the lather should be heavy and wet, which will require the use, in contrast to daily care, of copious amounts of water. A proper method of thoroughly cleaning with soap will be outlined in a succeeding paragraph, "Preparing Leather for Storage". Satisfactory soaps are considered to be:
Glycerin soap which is considered to be a superior cleaner and preservative, but relatively expensive. The imported item is usually better, although more expensive than the domestic, with the domestic constantly improving in quality.
Castile soap, which is an excellent cleaner, and the oils of which are excellent preservatives for long periods if the leather is given only normal usage.
Saddle soaps, which are made especially for the purpose of cleaning and preserving leather, many brands of which are satisfactory. Some imported saddle soaps are considered excellent but are expensive, many domestic saddle soaps being as satisfactory when the item of cost is considered. The saddle soaps to avoid are the cheap ones, which are apt to contain burnt fats, and which are likely to decompose into the soap's original components. If decomposition has begun (as is the case with some issue tins which have been in storage for long periods), leather cleaned with it will have a greasy feeling and will collect dust and dirt rapidly. The dust and dirt will not only be ground into the surface of the leather, causing it to deteriorate and discolor more rapidly than normal, but will also cause boots, breeches, and other items of equipment to become soiled quickly.b. Chemicals.-The purpose of all chemical cleaning agents is to dissolve the undesirable fats or fatty acid compounds that might be present in leather, to chemically reduce organic matter, to loosen coloring matter, or to bleach. Great care must be taken in their selection to insure using no agent that will have a deleterious effect upon either the surface or body of the leather. Among such undesirable agents would be strong acids or caustic alkalis; while among the agents considered suitable, in proper solution, are the following:
(1) Ammonia water, which is a solution in water of ammonia (a gas composed of nitrogen and hydrogen). It is highly volatile, and has a very characteristic penetrating odor. It combines with acids to from ammonium compounds, and with fatty acids to form ammonium soap, the most soluble soap and one of the best leather cleaners known. It also assists in loosening corrosion and verdigris from metal, and from leather stained by metal fittings, after which it may be more easily removed by soap or mechanical means.
Oxalic acid, which is a mild vegetable acid, formed generally by the decomposition of sugar by nitric acid. In proper solution, it is perhaps the best known and most generally used bleaching agent for leather, being used almost universally during the tanning process for the production of all so-called "blond" leather, and leather which, after bleaching, is to be dyed bright colors. The fact that it is a poison should be impressed on all using personnel, and its use supervised accordingly.
Alcohol (Wood or Methyl), which is a colorless liquid obtained by a process of distilled organic matter. It is an excellent cleaning agent or solvent, especially for "wet" or "dry" dyes, and, in addition, acts well as a "carrier" for bleaching agents. The fact that it is a dangerous poison if taken internally should be impressed on all personnel using it.
Acetic acid, which is a mild, colorless acid (C2H4O2) produced by the oxidation of common alcohol and many other organic substances. It is often useful in a weak solution for neutralizing the basic (alkaline) dye reactions in leather. Commercial vinegar is a dilute and impure acetic acid produced by acetic fermentation of dilute alcoholic liquids, such as cider or malt.The above chemicals may be purchased for the following approximate prices:
Oxalic acid crystals…………………15½ cents per gallon
Wood alcohol……………………….40½ cents per gallon
26° Ammonia water…………………60 cents per gallon
Preserving Agents - The most common preserving agents are enumerated below:
a. Dubbins are compounds usually of a rendered, unsalted animal fat, such as beef or mutton tallow, mixed with other preservative substances. When properly applied to the previously cleaned leather, they are considered excellent preservative agents, either in preparing leather for storage or, in some cases, for leather in daily use. Compositions of the more generally used dubbins are as follows:
(1) 20 lbs. beef tallow, ½ lb. rosin, 5 gals. inedible cod-liver oil, ½ lb. melted bees wax
Excellent forpreparing leather for storage.
(2) 50% beef tallow, 50% glycerin. Excellent preservative for leather in use.
(3) 40% mutton tallow, 60% prime neat's-foot oil. Excellent preservative for leather in use.
(4) 50% beef tallow, 50% prime neat's-foot oil. Excellent preservative for leather in use.
(5) 50% mutton tallow, 50% neat's-foot oil, small amount melted bees wax. Excellent preservative for preparing leather for storage.
In the preparation of all dubbins, great care must be exercised in rendering the unsalted tallow to prevent the burning of the fats, which would make the resultant tallow, and therefore a dubbin made from it, unsuitable. In order to remove as many impurities as possible, the suet should be cut into small pieces and put into a suitable utensil, with sufficient water added to prevent burning, and rendered out slowly, all cracklings (pieces of flesh, etc.) being removed as they appear on the surface. After rendering, the melted tallow should be strained first through a coarse colander and finally through a very fine colander, then allowed to cool and solidify. After solidifying, the tallow should appear white and clean. The water which will be at the bottom of the container should be removed by piercing the layer of solidified tallow with an ice-pick or other implement, and turning the container upside down to allow it to drain off.
In order to prepare all dubbins, the ingredients are heated together until melted sufficiently to mix well, preferably in a double boiler, to avoid burning the fats. It is best after they are prepared to place all dubbins in small containers, such as olive or pickle jars, so that during the process of their use the contents can be shaken to insure their being properly mixed when applied.
Before applying the dubbin it should be melted by heating in a double boiler and then it should be allowed to cool until lukewarm (never above a temperature than can be borne by the hand) and applied to the leather with a small sponge, piece of sheepskin, or other suitable agent. The applicator should be saturated with the warm, thoroughly mixed dubbin, and the dubbin applied to the article, first spreading it quickly over the entire surface of the still slightly damp (previously cleaned) leather, then rubbed in well by band. Any excess that remains after a short time has been allowed for the dub-bin to penetrate the leather should be wiped off with a clean, dry cloth. The leather is then ready for storage, or if to be used currently, the oil should be allowed to penetrate for a period of about twenty-four hours, after which the excess surface oil should be removed by a cleaning with soap before the leather is dressed and put into service.
b. Glycerin is a clear, colorless liquid of thick syrupy consistency, made by the hydrolysis of animal fats or fixed oils, purified by distillation (as by action of super-heated steam on palm oil). It is slightly antiseptic, and is a solvent for fixed alkalies or alkaloids. It is an emollient, hygroscopic (absorbs moisture from the atmosphere), does not evaporate or become rancid, and is much used as an ingredient of lotions and ointments. Mixed in proper proportion with other substances, it is considered an excellent leather preservative and softener.
c. Oils suitable for preserving leather may be animal, vegetable, or mineral derivatives, but generally the animal oils are considered superior, with few exceptions, for this purpose. Among the more generally used oils are the following
(1) Neat's-foot oil, which has long been recognized as the best of all oils for leather. It is a pale yellow, fixed oil, made by boiling the feet, less hoofs, and skin bones of "neat" cattle (cattle of the ox type as distinguished from horses, sheep and goats). It is the preservative base of many saddle soaps and an ingredient of many oil polishes. Due to the fact that it is difficult and expensive to obtain in its purest or "prime" state, many commercial products termed "neat's-foot" are likely to have been "cut" with some mineral oil.
(2) Petroleum jelly, which is obtained from refining mineral crudes, applied very lightly to leather surfaces is believed by some to protect leather equipment from the harmful effects of sea air during overseas shipment. Useful for this purpose also would be any of the more generally used dubbins, to which a small amount of paraffin has been added.
(3) Castor oil, which is generally obtained from the castor bean, but may be derived chemically from other sources. Chemically, it is a combination of glycerin, fatty acids, and ricinoleic acid. The acids in castor oil are undesirable constituents of an oil to be used in preserving leather, but many officers have used castor oil with great success in dubbins, and in combination with saddle soaps. In these cases, the undesirable acid effects of the oil are apparently neutralized, at least to a large extent, by the combination of the acids with the fats in the dubbin or with the alkalis in the soap. If used with the soap, caution is recommended in the amount applied, for if too large an amount is applied, or if allowed to penetrate too long before soaped, the leather is likely to be so softened, as for example in the case of saddle skirts, that the "body" of the leather is lost, and its strength undesirably reduced. Like glycerin, however, if used properly, castor oil has the advantage that it will not appreciably darken the leather on which it is used.
(4) Other oils known to be good leather preserving agents, but which either are likely to excessively darken leather, to turn rancid, or to be too expensive, are olive oil, unsalted butter, and palm oil.
Itmust be realized that the application of any oil will darken, to an extent, any previously bleached leather, and that too much of any oil is deleterious to leather and will greatly lessen its tensile strength. In this last connection, it might be said that more leather equipment has been ruined, or its serviceability impaired, by the application of too much or too hot oil than ever by the application of an insufficient amount. In order to properly apply any oil, a piece of woolen cloth, such as a small square of salvaged blanket, should be dipped into the preferably warm but never hot oil, squeezed out, then passed lightly over the whole surface of the almost, but not quite dry, previously cleaned leather, and finally the surface oil rubbed in by hand. After oiling, the oil should be allowed to penetrate, and the leather "dry out", which may take twenty-four or more hours. Thereafter, especially while in storage, any excess oil appearing on the surface of the leather or exuding from its pores, should be removed with a clean, dry cloth. Before being "dressed", any excess oil remaining on the surface of the leather should be removed by cleaning with soap.
d. Dressings or polishes are used not only to assist in preserving the leather but to give it a luster. Any of the better grades, applied according to directions, should be satisfactory. If it is desired to make a polish, the following formula would probably prove satisfactory:
Melt together 55 parts of carnuba wax and 55 parts of crude montan wax (221° F.) ; add 10 parts nigrosine base (for black leather), or 10 parts other color dye-stuff soluble in oil (for other than black leather), dissolved in 20 parts stearic acid; then add 150 parts ceresine (a form of wax) and finally 900 parts oil of turpentine.
e. Waxes have for their object the imparting of a luster to the leather, as for inspection, etc. Any standard grade of wax, or wax polish, should prove suitable, provided no "wax cleaner", which might contain ingredients injurious to leather, is used. The wax should generally be applied with a very slightly dampened soft cotton cloth that has been impregnated with wax, the leather being given a very light coat. Then, before the wax is dry, it should be spread with a soft brush, and the final polishing given with a soft woolen cloth.Care of Leather Equipment - General
7. SERVICE REQUIREMENTS.-Regarding the requirements in the service as to the care of leather, we find, generally, that in the field our main consideration is to keep the equipment serviceable, without regard to a high state of appearance. To do this, however, under campaign conditions is, as every soldier knows, difficult. Constant exposure to weather (sun, wind, and rain), mud, road water (moisture, decaying organic matter, dirt, etc.), sweat, and extremely hard usage, combines not only to wash the essential preserving oils from the leather, but to grind into it substances that cannot be considered otherwise than deleterious. If, therefore, we can, in the field, keep our leather clean, protect it in camp from weather as much as possible, and periodically renew its oils, we should be able, not only to preserve it and maintain its serviceably, but return with it to garrison after a period of extended field duty in such a condition that we can, with a minimum of labor, bring it back into what might be called "garrison shape." By garrison shape we mean a condition in which the leather is not only serviceable and constantly ready for campaign, but also in which the leather is of nearly uniform color and can be readily brought, despite daily use, to a high state of appearance, as for Saturday inspection, parades, reviews, etc.
While it may seem that these requirements are somewhat in conflict, it is nevertheless believed that they can be met by following one of the methods for care and preservation to be outlined. At the outset, it must be stated that, if the leather is not too far gone from the effects of hard usage, neglect and previous dyeing, particularly if the dyes have been burned into the surface of the leather, there are many ways in which this may be done. Any method that meets the requirements is at least a satisfactory one. Experience over a long period of time, under all conditions, is the only laboratory for establishing the relative merits of any one method. Likewise is the same statement true in regard to the selection and use of cleaning and preserving agents, a wise and very old rule to follow being: "Put nothing back into the leather that was not taken from it during the tanning process." Also are we concerned with the availability and cost of materials, which limits us to the use either of issue items or those that can be otherwise universally and cheaply obtained. Fortunately, it can be said that all issue items that meet government specifications are of excellent quality, and that their correct use will go far toward meeting the requirements previously mentioned.
8. EQUIPMENT IN STORAGE. All leather equipment in storage should be kept in a cool, dry place; and, depending either upon excessive aridity or excessive rainfall, should be inspected periodically as follows:
(1) In temperate climes - once or twice a year.
(2) In semi-tropical climes - two or three times a year.
(3) In tropical climes - three or more times a year.
Where inspections disclose the following-named conditions, the procedure should be as follows:
(1) Dampness.-Hang or place the damp article in the sun or other dry place where there is a free circulation of air, but do not leave exposed to the sun after the dampness is gone.
(2) Mold.-Remove all mold (a fungus growth, which if allowed to remain will destroy the leather fibers) immediately by wiping with a moist cloth and allowing the article to dry by exposure to air before returning to storage.
(3) Excess oil.-Inasmuch as too much oil is detrimental to all leather, all oil that appears on the surface of the leather, or exuding from the pores, should be wiped off with a clean, dry cloth.
(4) Dryness.-Since no leather should be allowed to dry out entirely, if found so (hard, brittle, lacking "life"), it should be given a light re-application of dubbin, any excess of which should be wiped off before restoring.
9. EQUIPMENT IN SERVICE.-Generally speaking, all serviceable equipment in daily use can be maintained perfectly by a proper daily cleaning with a good grade of soap as soon as possible after use. This should always be done before sweat, mud, etc., have been allowed to dry and harden, which not only subjects the leather to the deleterious effects of these substances, but makes cleaning much more difficult. It should also be given a periodic polishing with a good grade of leather dressing. A thorough cleaning and reoiling two or three times a year is also necessary, depending upon usage and climatic conditions. Good grades of saddle soap and leather dressing both contain oils that, if used correctly, will preserve leather for long periods of time with normal garrison usage under normal conditions.
10. GENERAL.-In order properly to clean and preserve any leather equipment, proper facilities must exist. Mention has already been made of the fact that a sufficient time allowance must be made; in addition, and most importantly, a place must be made available, equipped with proper cleaning racks, tables, and all other necessary equipment; and finally, this place for cleaning equipment should not be the place where the equipment is kept. In other words, the cleaning room should be separate and distinct, though adjacent to the tack room In organization stables where such facilities do not exist, experience has proved the advisability and made worth while the devotion of thought and effort to establishing such cleaning rooms. These rooms not only result in a great saving of time and energy on the part of the men, but in much superior equipment, for it is a well-recognized fact that equipment once in perfect shape is easily kept in perfect shape.
11. NEW EQUIPMENT.-When withdrawn from storage and issued to troops, all new government issue leather equipment is in more or less of a dehydrated state of preservation, maintained by an agent (dubbin), that not only by closing the pores of the leather, excludes most atmospheric moisture, but retains almost indefinitely the natural preserving oils tanned into the leather at the time of manufacture. As long as items of issue that have been "dubbed" remain in storage and are not put into daily use, this coat of dubbin should not be removed, due to the fact that it is an almost perfect leather preservative. However, before the item can be put into comfortable use, it will usually be found necessary to "break it in" by removing this protective coat of dubbin and by restoring the natural life and flexibility of the leather by additional oiling, cleaning and reoiling, if necessary, during a short period of normal use. The fact that a short period of normal use is absolutely necessary in order to break in new equipment cannot be too strongly emphasized, for any known method of shortening the "breaking-in process" is likely to result in getting too much oil into the leather, the deleterious effects of which have already been discussed.
In order to put such new government issue items of equipment into use, the following process is recommended:
a. Make a saturated castile soap solution by dissolving in hot water as much shaved castile soap as possible. Add eight to twelve tablespoonfuls, depending upon how hard the water may be in the locality, of strong ammonia water (26° U.S.P. or 28% ) to about one G.I. mess cupful of the saturated castile soap solution. Then add sufficient water to make one gallon of the castile soap and ammonia solution.
b. Thoroughly scrub the article with the castile soap and ammonia solution. A nail brush, or a brush no stiffer than a nail brush, is best to use for this purpose. A stiff brush, such as a G.I. scrubbing brush, is considered too stiff as it is likely to mar the surface of the hair, or grain, side of the leather. The ammonia and soap solution should produce a heavy lather. ]f it does not, more ammonia or more soap solution, or both in small amounts, should be added until a heavy lather is produced. If mixed and used properly, the ammonia and soap solution will dissolve and clean the surface of the leather of dried waxes and oils; it will also assist in loosening verdigris (a copper salt) and metal stains.
c. Rinse off thoroughly with clear water, wipe as dry as possible with a clean cloth, and allow to dry.
d. When almost but not quite dry, apply either dubbin or oil in the manner previously described, (par. b) and allow to dry thoroughly. This drying and absorbing process may require 24 or more hours in a heated room, during which any excess or exuding oils should be wiped from the surface.
e. When thoroughly dry, again clean the exposed surface of the leather of excess surface oils with a very light soap lather. The saddle is now ready either for normal use or to be dressed, if dressing is desired.
f. When thoroughly dry from the previous step, apply leather dressing, if desired, according to directions. If the first application of dressing does not give the luster desired, allow itto set and the oils to penetrate for a few hours; the surface of the leather may then be gone over with a slightly damp cloth and re-dressed. -
g.If a particularly high standard of appearance and luster is desired, it may be obtained by waxing, as previously described, after the second application of dressing.
12. USED OR REPAIRED EQUIPMENT.-In order to put used or repaired equipment that has been in storage into use, or to periodically refinish equipment that has been in use, the following process is recommended:
a. Thoroughly clean with the ammonia and soap solution, as described in paragraph 11.
b. Dissolve four to eight tablespoonfuls crystallized oxalic acid, depending upon the condition of the article and whether or not it has been previously dyed, in one pint of wood (methyl) alcohol, and add sufficient water to make one gallon of the solution. Using this solution on a clean sponge, rag, or soft brush, thoroughly go over both hair (or grain, as it is sometimes called) and flesh sides of the leather, particularly where discolorations are evident. Continue the process until all remaining oils, greases, as much dye-stuff as possible, and organic matter are dissolved and washed out, and the surfaces clean.
c. Not later than fifteen minutes after the preceding step, thoroughly reclean with the ammonia and soap solution. (This not only neutralizes the oxalic acid, but assists in washing out of the leather those undesirable substances loosened by the oxalic acid-alcohol solution.) Rinse thoroughly with clear water, and wipe as dry as possible.
d. If the surface of the leather appears to darken after the preceding step, due to the presence in the leather of basic dye-stuffs, sponge the leather off with a mild acetic acid solution; made by mixing one tablespoonful of acetic acid, or one pint ordinary household vinegar, with sufficient water to make one gallon of the solution.
e. Allow the equipment to dry out in a heated room. This drying process may take twenty-four or more hours in a room kept at about 70 F.
f. If, at this time, the leather is not bleached sufficiently to insure a good, natural color, steps b, c, d and e may be repeated before the equipment is oiled, but never should the oxalic acid be used either in stronger solution, nor more than three times on any given set of equipment. If the equipment is so badly stained or dyed, or the dye burnt into the surface or fibers of the leather, that three oxalic acid solution applications do not bleach sufficiently, the chances are that the dye pigments are so thoroughly imbedded in the gelatinous tissues of the leather that to remove them would ruin the leather.
When sufficiently bleached and almost but not quite dry, oil as previously indicated, allowing the oil to penetrate and the equipment to dry out in a heated room for twenty-four or more hours.
g. If, after oiling, there are any surfaces of the grain side that are rough and have been worn through to the inner fibers, these surfaces may be refinished and made smooth by the following process, after the surface oil has been removed by cleaning with a very light soap lather:
(1) Mix thoroughly three heaping tablespoonfuls of powdered gum tragacanth and one heaping teaspoonful of pulverized oxalic acid crystals. Stir this mixture into one quart of water and let it set (about twelve hours) until about the consistency of soft jelly or gelatin.
Apply this compound with a small sponge, rubbing it well into the surface, always in the same direction, and finish by allowing it to dry slightly and then rubbing hard with a dry cotton cloth. This will lay and fix all of the exposed rough fibers and leave a smooth surface, which will be an excellent base for a later dressing.
(2) The same results can be accomplished by the use of any other commercial leather cleaner, the principal base of which is powdered gum tragacanth, mixed with a small amount of oxalic acid in the same proportions as described above, and applied in the same manner.
h. Stain if desired, and dress as previously indicated.
i. Apply wax, if desired.
To summarize the effects of the various chemicals in this process, the ammonia and soap solution neutralizes and washes away fatty acids, dirt and grit, and organic matter; the ammonia, as well as being a neutralizing solvent, acts as a soap "builder". The oxalic acid-alcohol-water solution kills molds and mildew, runs dyestuffs, and bleaches. A re-use of the ammonia and soap solution neutralizes traces of any remaining acids, preventing any harmful effects either on the leather or stitching, and washes out any residues. The mild acetic acid solution, which soon harmlessly evaporates without trace, neutralizes the alkali effect on any basic dyestuffs that might previously have been used. The oil softens and preserves. The refinishing lays and binds exposed fibers and smooths worn surfaces. The dressing preserves and finishes The wax preserves by protecting the finish and gives a high luster.
13. EQUIPMENT IN SERVICE.-Once equipment is in proper shape, it may be easily kept in shape by a daily cleaning immediately after use with a good soap, which should be used generally with a minimum amount of water; by periodic dressing or polishing, as desired or required; and by a periodic thorough cleaning, refinishing and oiling, as previously described. Depending upon conditions and use, it should not be necessary to completely refinish and reoil more than once or twice a year.
14. STORAGE OF LEATHER EQUIPMENT.-Before putting used leather equipment into storage, it should be thoroughly inspected, repaired, if necessary, then cleaned and oiled as follows:
a. Articles of Black Leather. Remove all hardened grease with a thin piece of wood (do not use a knife or a piece of glass) and dampen a sponge in clear, lukewarm water (hot water must never be used nor the leather allowed to soak in any water), and pass the sponge over the article until all dirt and sweat have become soft (rinse the sponge often, and frequently replace dirty water with clear). Clean thoroughly by obtaining a good lather with harness soap and giving the article a heavy coating, continually rubbing the lather into the article until all dirt and sweat are removed. Rinse thoroughly with clear water and a clean sponge, wiping away all excess moisture. When leather is nearly but not entirely dry, apply warm dubbin, made by one of the processes previously described. If ammonia is available, the ammonia-soap-water solution may be used instead of harness soap for cleaning.
b. Articles of Russet Leather.-Proceed exactly as outlined for black leather, except use saddle soap instead of harness soap, or use the ammonia-soap-water solution, if available.
Inasmuch as it is not possible, during the tanning process, to stuff russet leather with oils to the extent possible with black leather, it might be further stated here that russet leather equipment will need more frequent oiling and better general care than black leather. (From this fact might be deduced a conclusion that black leather, if color were not a consideration, would be a more practical leather for service requirements. It would, all other things being equal, be always of a uniform color, and much easier to properly maintain under all conditions, garrison or field.)
C. Metal Parts.-Wash with warm water to remove saliva, sweat, mud, etc.; polish any rusty article; wipe thoroughly with a cloth slightly moistened with oil, so as to leave the surface of the article covered with a thin oil film.