HAND-CRAFTED LEATHER GOODS
How Leather is Produced - continued
There are literally hundreds of tanning methods and recipes dating right back through the ages.
You can make soft, washable leather with emulsified oils and woodsmoke. This is commonly known as brain, smoke or Indian tanning. Animal brains are traditionally used as the source of emulsified oils, hence the name, but you can also use eggs or a mixture of soap and oil. Brain tan is ideal for clothing, bags, beadwork and all kinds of things (such as shoe-laces, pot holders, hair ties, or holding parts of your truck together).
Brain tanning is the most popular method for home tanning. The tools and tanning agents are common and easy to get, the entire tanning process can be done in a matter of days, and the finished product is incredibly strong, soft, durable, washable and warm. It cuts the wind, allows your skin to breath and stretches with the movement of your body. When a hide is brain tanned with the hair and grain removed it is known as "buckskin".
Buckskin can be made from any of the hoofed animals including deer, elk, antelope, sheep, goat, buffalo, even cow (it is the way that a skin is tanned that makes it "buckskin", not the fact that it is made from a deer hide). This is also a great way to tan furs.
Buckskin is particularly valued for being durable and comfortable when made into outdoor clothing, plus, being excellent for making pouches, moccasins and many other items. Unfortunately it is not waterproof.
In 1884, Augustus Schultz, an American chemist, discovered that chromium salts used in the tanning process made the leather far more resistant to moisture and sped up the manufacturing process. The development was so important that chrome tanning is still in use today, more than 100 years later.
Where animal skins and hides in centuries past had to be
prepared and processed immediately to retard the decaying process, modern refrigeration and curing
methods allow todayís leather manufacturers to hold hides and skins until they are needed.
When he is finally ready to use the hides, he transfers them to what is called
the "beam house". There the hides are soaked in huge vats or drums filled with
water. Gigantic paddle wheels or turning drums keep the hides constantly in
motion. Lime and sulphides are added to this solution to aid in the removal of the animal hair.
The lime solution is then removed from the hides. (By this time, the chemicals
with their high pH have caused the hides to swell to about twice normal thickness and
they bear no real resemblance to leather as we know it).
Once the hair is removed and the lime solution washed away, the skin can be
fleshed and trimmed to remove the portions which do not make good leather, or
which would interfere with the actual tanning process. Now the hides are again
washed to remove any residue from the previous steps.
The hides are now almost ready for tanning. The previous steps have
created a swollen skin which would not accept the tanning agents well. Now, salt
and acid are added to the liquid solution to attract and tie up the excess
moisture. The "pickling" is a preserving technique, as well, and hides in this state can
be kept for extended periods of time without fear of deterioration.
The hides are now ready to tan, and in many cases, the same vats or "mills" in
which the hides were prepared are used for the "chrome tanning" process. The
tanning agents or chemicals react with the hide protein and really make it into
leather as we know it.
In the past, many of the steps in processing and tanning the hides were done manually — and in some countries and tanneries, this is still the case. But, today, much of this can be done using sophisticated equipment to measure and control the mix of chemicals used in wet processing and tanning.
Chrome-tanned sheep and deer skins are currently marketed as "buckskin" even though they have very different physical properties than the traditional material. (Pollution of waterways is the number one problem facing the modern leather tannery (as well as the folks down-stream), and chrome compounds are the culprit. Chrome tan doesn't allow your skin to breathe which makes it very sticky and clammy against the skin. It's also broken down by the alkalinity of perspiration and soaps (on the other hand, you can boil chrome tan and it won't affect it a bit, in fact this is a common test to make sure the hide is fully tanned). I personally think that those black leather jackets folks wear are pretty smart and comfortable. But I wouldn't recommend it for much else. Most home tanning books teach you how to do this type of tanning. However, besides making an inferior leather and polluting the environment, you also have to special order and deal with these very hazardous chemicals. You're better off brain-tanning.) In the production of chrome tanned skins and hides, the chromium sulphate binds very strongly to the fibres. The resulting complexes are very stable, and this enables the tanners to remove the water both mechanically, and then still further by the use of vacuum drying. In vacuum drying, the skins are flattened out on a heated bed, a cover is then placed over the skin, and the air pumped out. The subsequent partial vacuum that is formed allows the water to be "boiled off" at a substantially lower temperature in a matter of a few seconds. The resulting chrome tanned leather has a strong blue colour, is damp to the touch, but certainly dry enough for sorting with a good degree of accuracy. Chrome tanned hides and skins can therefore be dried, sorted and back into production within one day of tanning. This allows a very fast throughput of skins, minimising the amount of stock necessary to allow the tannery to operate. Traditional methods have not been industrialized because the tanning process relies on physical manipulation more than chemicals. This leaves it in the domain of the backyard tanner, where it has long been. The mystique and reputation of buckskin remains strong however, and commercial interests will continue to cash in on it.
Alternative vegetable tanning methods can replace chrome tanning to a high degree. An example is the "Liritan" process, developed in South Africa. A high chemical uptake, low pollution load, uniform penetration of the tan and a shortened process time with consequent financial efficiency are claimed to be the main advantages of this process (Higham, 1991), but little is known of the practical implications.
The Liritan process is a common method used in the U.S. for producing skinning leather. The leather is pre-tanned with Calgon (sodium hexametaphosphate) prior to tanning with vegetable tannins. Skirting was traditionally produced by moving the hides from pits with weak tanning solutions to pits with successively stronger solutions to give even tanning. The traditional pit method of vegetable tanning is slow. The Liritan process allows the tanner to use a strong vegetable tanning solution immediately after pre-tanning. Thus, the hides are tanned more quickly and thus less capital is tied up in the process.
Synthetic-tanned leather is tanned using aromatic polymers such as the Novolac or Neradol types. This leather is white in color and was invented when vegetable tannins were in short supply, i.e. during the Second World War. Melamine and other amino-functional resins fall into this category as well and they provide the filling that modern leathers often require. Urea-formaldehyde resins were also used in this tanning method until dissatisfaction about the formation of free formaldehyde was realised.
Painting:- A process for loosening hair or wool (usually the latter) which is employed with skins whose protective covering is so valuable as to make it desirable to avoid injuring it by soaking in a lime liquor. The process is carried out by painting the flesh side of a skin with a depilatory substance, containing sodium sulphide or arsenic. Nowadays this is the usual method with sheepskins bearing the higher grades of wool. Before it was invented, such skins were usually de-haired by sweating.
Tanning Rabbit Skins
This is a method of tanning hides that is low on costs and labour compared with other methods of "custom tanning". You can use this method to tan rabbit skins as well as goat skins. The procedure can be used for all kinds of mammal pelts when you want the fur to remain on the skin. The result is a soft, workable hide, which can be used as is, or be cut up for sewing projects.
Skinning small animals, like rabbits, are easier to work with if they are hung by their back legs even if they will skin cleaner being skinned from the head down. If several are to be skinned hammer two 3Ĺ" long nails (16 penny) into a fence rail before cutting their heads off and bending them upwards. Now hang the rabbits by pushing the nails between the Achilles tendons and the leg bones on the hind legs with their underside towards you.
Salting Fresh Skins
Fresh hides right off the animal should be allowed to cool immediately. Trim off any flesh and scrape visible fat from the hide. Place the skin in the shade, ensuring it lies completely flat with the fur side down, preferably on a cold surface. When the skin feels cool to the touch, cover the flesh side completely with plain, un-iodized, salt.
Do not be stingy in your use of the salt.
If skins aren't salted within a few hours of removing the flesh you might as well forget it. They will have begun to decompose and will probably also lose their hair during processing.
Keep the skin flat and out of the reach of animals. You don't need to stretch the skin, just make sure it is perfectly flat, without curling at the edges. If you lose a lot of salt while moving the pelt, add more. The salt is to draw the moisture from the skin so liquid may pool in low spots. Just add more salt. Let the skin dry until it is crispy. This will take from a few days to a couple of weeks. When completely dry, the skin is very stable and won't change or deteriorate appreciably.
When you're ready to tan the skins, get together the following:
7 gallons water
2 pounds of bran flakes
16 cups plain salt (Industrial Vacuum Salt, not iodized) (Have a look Here).
2 large plastic rubbish bins (30 gallon) and one lid (Have a look Here).
a 4' wooden stirring stick
3Ĺ cups battery acid (from a car parts shop or, have a look Here).
2 boxes baking soda (Have a look Here).
wooden rack or stretcher
neatsfoot oil (Have a look Here).
wire bristle brush
This recipe makes enough tanning solution to tan ten rabbit skins. (Reduce the amounts by half for fewer skins).
Mixing the Solution
A couple of hours before you plan to begin, soak the dried skins in clear, fresh water, until flexible. Boil three gallons of water and pour over the bran flakes. Let this sit for an hour, then strain the bran flakes out, saving the brownish water solution. Next, bring the remaining four gallons of water to the boil. Put the 16 cups of salt in the plastic dustbin. Pour the water over the salt and use the stirring stick until the salt dissolves, add the brown bran liquid, and keep stirring.
When the solution is lukewarm, you are ready to add the battery acid. Read the warning label and first aid advice on the battery acid container. Wear gloves and an old, long-sleeved shirt, and carefully pour the battery acid down the inside of the dustbin into the solution – do not under any circumstances allow it to splash. Stir the battery acid in thoroughly.
At this point, you can peel off the hide's dried inner skin, or, if you have fresh skins, use as is. Add the skins to the solution and stir, pressing the skins down carefully under the liquid until fully saturated. Leave them to soak for about 45 minutes, stirring from time to time to make sure every part of the hides are exposed to the solution. During the soak, fill your other dustbin with fresh, lukewarm water. After 45 minutes, soaking is complete.
Using the stirring stick carefully move the skins one by one into the other dustbin containing the lukewarm water. This is the rinsing process, for removing the excess salt from them. Stir and swish around the skins for about five minutes, but change the water as soon as it begins to look dirty.
Adding baking soda at this point will neutralize some of the acid in the skins - this is advisable because there will be less possibility of residual acid in the fur to affect sensitive people. However, this also may cause the preserving effects of the acid to be neutralized. So you choose to use baking soda based on your own end use of the skins. If the skins or fur will spend a lot of time in contact with human skin, it's worth using the baking soda. If it's to be used be used for a rug or wall hanging, I probably wouldn't.
They will be very heavy when you lift them from the rinsing water. Let them hang over a board or the back of a chair or other firm surface to drain. Now, using a sponge, rag or paint brush, swab the still-damp skin-side of the hide with an ounce of neatsfoot oil. It will be absorbed quickly, leaving only a slight oily residue. Tack the hide to your "stretcher." Gently pull the hide as you tack it so there's some tension in the skin. No need for excess pressure or overstretching. Leave the hide in a shady place to dry.
Your acidic tanning solution can be neutralized for disposal by adding a couple boxes of baking soda. It will froth and bubble vigorously and release a potentially toxic gas, so allow plenty of ventilation and keep away from the solution while this is happening. Save it for use in your garden, on your pathways and suchlike, to keep them clear of weeds. Do not pour it down your drain.
Check the hide every day. When the skin side feels dry to the touch in the centre, but still flexible and somewhat soft, take it down from the rack. Lay the fur side down and go over the skin with a wire bristle brush. This softens the skin and lightens its colour. Don't brush too heavily or excessively in one spot, just enough to give a suede-like appearance. After this, put the skin where it can fully dry for a day or so longer.
Tanning a snakeskin is labour intensive and rarely comes out the way you would picture it in your mind or with a product finished like a glove-soft commercial quality skin!
The first and perhaps most important step is fleshing the skin. This can be accomplished only with "elbow grease" and stamina! Place the "green" skin on a flat surface and scrape it completely with a tool of choice that most readily removes virtually all of the tissue adhering to the skin. A finished skin is a white skin! Some fleshers prefer variously a knife, a meat cleaver, a spoon, a putty scraper, and a host of other devices designed to get flat down on it and remove the stubborn tissue. By stroking the skin with the grain downward toward the tail, it seems to do less stretch damage to the skin or scales on the opposite side. Trim the tail carefully by inverting it so the tip is preserved as a part of the skin. Staple the skin on a board or flat surface without unduly stretching it. Leave it in a straight position so that you end up with a straight skin, a natural shape without curves. (Have a look here).
Do not put salt on a snakeskin! There are several good commercially available tanning solutions (too numerous to list, but have a look in the Tandy Leather mail order catalogue) to apply to the wet skin after stapling flat.
After the skin has dried, remove and rub, or break it, over a surface corner like a table edge - much like a shoeshine buffing rag. This last step is not necessary if you are planning a wall mount display. Just mount the skin on the desired board and be done with it.
Tanning fish skins
There are those who say fish skins being tanned for leather have to be treated almost like hair-on skins being tanned for leather. The scales and outer epidermal layer of skin is removed by using a lime solution, then its de-limed, pickled, degreased (a must!), shaved, neutralized (depending on what tanning agent you use), tanned, oiled and then worked soft. Although you do not retain the original colour and markings, nevertheless you have a nice piece to work with. Unfortunately not a large piece however, because normally the fins, and extras are trimmed off.
That said you can always have a stab at the following.
Some considerable time ago I did look into methods of tanning fish skins and most of them are laborious and time consuming. You may think the following is a wind-up, but I assure you itís not.
There is a method used by the Inuit that gives, Iím told, good results, using salmon, trout and most smaller fish skins and does not smell after preparing. The king salmon is used for boots, heavy-duty boots. Only female silver salmon is used for hats for girls. And the pike skin is for water jugs. The trout is for bags. You take the skin off and soak it in the water, and then you scrape it with a sea shell. Some fish you have to scale; some fish you don't. Like pike and white fish, you've got to scale it, you soak it in urine.
Urine contains formic acid and urinase, and uric acid, among other things. These acids have a preservative effect on the skin. When urine is left to stand ammonia is formed, which is a strong base. If a hide sits in urine for some time, the basic environment will begin to have a dehairing effect. The ammonia influences the skin by splitting the naturally occurring fats, to form glycerol and free fatty acids. These free fatty acids can penetrate the hide and react with the fibres of the dermis; the skin is tanned. When ammonia is used as a cleaning liquid, it is its saponifying properties that are being exploited.
What you do is this. Pee a couple of times in a bucket, (although a womanís urine is said to be superior) let it sit with a lid on for a day or so, to bring the ammonia out, which draws the fat out of the skin. Then pour in the same amount of water as you have urine, half water half urine that is. Put your skins in it after taking all the flesh off with a spoon or a dull knife, but not at this stage the scales. Trim off the fins etc. Let them sit in the fluid while stirring once in a while for about 12 – 24 hours depending on how thick the skins are.
Then wash them out in lukewarm water using shampoo or a mild soap. When washed, the scales on the surface of the skins, are easily rubbed off. After they are washed the skins need to be flattened out on a piece of board, stroking down towards the tail. Seemingly they stick like glue to the board until dry, then they fall off.
When they are completely dry comes the tedious part of the job. You must scrunch the skins in every direction possible to break the fibres as much as you can, to make them soft enough for sewing. Also you can draw the flesh side over a not too sharp edge to get it smoother. They really do turn out great apparently and not smelly. One thing to remember is not to get the skins wet afterwards, otherwise they will become hard. You can use textile waterproofing on them.
Fish leather is the second strongest leather known to man. Three strips of certain fish, Ĺ inch wide, braided together, can pull an automobile apparently.
A very good book is Leather. Preparation and Tanning by Traditional Methods, by Lotta Rahme, 112 pages, published by Caber Press, ISBN 1-887719-00-8 and I believe costs about £20.00. She has a small tannery outside of Stockholm, Sweden, where leather is tanned using traditional methods and techniques. From this leather she sews costumes, often replicas of historical leather findings for museums, but also such merchandise as belts, bowls, bracelets and bags.
One of her books
Curing a Goat Skin
The skin should be as free from fat as possible, any adhering pieces being scraped off with a blunt knife. Place the skin fur down on three or four folds of newspaper. Mix, in equal proportions by measure, salt, saltpetre (or its present day equivalent) and powdered alum. See Here. A tablespoonful of each will be ample for a small skin. Rub the mixture well into the skin with the three middle fingers, going carefully round the edges. The salt must not get into the fur or this will sweat. Having been all over the skin, place three or four folds of newspaper at the top and roll up tightly, tie a piece of string round the middle and put away for 10 days to a fortnight. Afterwards, with a blunt knife, peel off the inside skin. This should come away quite easily and leave a chamois skin, soft and pliable.
After the tanning, the next stage is the preparation of the tanned hides for its necessary smoothness, colour and flexibility. This is called currying. Probably originating from the old French word "correer", meaning "to make ready". Traditionally this was done by specialised craftsmen.
The tanned hide has to be rinsed in fresh water over a period of several hours. Between each rinse the water is squeeged out of the hide using a slicker. The object being to remove as much unfixed tannin as possible. At the same time you must be careful not to tear the grain off.
Next, dry the hide off a bit, then grease and soften. Dyeing comes before oiling.
Dyeing:- Vegetable-tanned hide at this stage is whatever colour has been imparted by the tannins. To change the colour of the hide you can soak it in any tannin-based dye.
Oiling:- As well as making it softer and darker, oiling also prevents it from cracking. Using a waxy, animal, body-fat, also imparts a heavier feel, as well as making it more resistant to water. A light oil, such as neatsfoot oil, gives a much more stretchy, lighter leather.
When the hide is dry, it can be dampened by rolling in damp towelling or hessian type material. This process, the oiling, stretching in all directions, then drying, is repeated until the necessary softness is acquired. The terms "staking" and "perching" are the names applied to other processes by which a hide is stretched, softened and made more flexible. The leather is drawn back and forth over a blunt, horizontal blade fixed on an upright stake, whilst in perching, a hide suspended from a perch has a blunt blade drawn over it.
It is in comparatively recent times that machinery has taken over from the hand operation, though not totally, as the hand method is still the method of choice for some very light leathers.