Curing/Hardening leather?

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wat the tyler
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Curing/Hardening leather?

Postby wat the tyler » Sun Jan 14, 2007 12:17 pm

I have a question which I hope can be answered.

I need an easy way of making a piece of leather harder ie. less soft and more rigid.

Is there a quick way of doing this? ie like boil it in salt water or something?

Thanks in advance.


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Postby gregory23b » Sun Jan 14, 2007 1:54 pm

What are you using it for?

You can make small pieces of say shoe sole bend quite rigid by wetting and forming round a jar, letting dry, dries to shape and then waxing and waxing (with some heat), makes it nice for bracers.

You are not thinking of armour are you??

Don't boil it, it will shrivel and crinkle and go rock hard but be totally distorted and be like a concrete leather quaver.


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Postby Dave B » Sun Jan 14, 2007 2:30 pm

Don't boil it, it will shrivel and crinkle and go rock hard but be totally distorted and be like a concrete leather quaver.


there are techniques that do involve cooking the leather (probably short of boiling) which produces cuirbouille (sp) literally cooked leather. a freind who was into shooting used to make holsters this way and they were very impressive. below is an article by an SCA chap.


http://www.daviddfriedman.com/Medieval/miscellany_pdf/Other_Articles_VII_PfctImpd.pdf


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Postby Neibelungen » Sun Jan 14, 2007 3:10 pm

Part of theproblem comes from the fact most people are using veg tanned leather, which is somewhat different from the medieval oak tanned pit leathers (takes between 6 and 18 months to be made). Esentially it's a thinner version of traditional soleing bend.

Hot water (less than boiling) will give you a pretty solid leather, but it makes it extremely brittle and prone to cracking. The heat is cooking the leather fibres, removing the oils and waxes that make it flexable and elastic.
However it does make it very stiff.

The other two ways are simple wetting and allowing to driy , or forced drying using an oven at less than 45C. Above this you are again destroying the leather and risk cracking and splitting.

The body of the leather can be stiffened while wet by compression, either hammering or burnishing.

This won't give the same stiffness as the hot water method, but it will survive a lot longer and be less prone to breaking as it still retains some flexibility.

In all cases you'll get shrinkage. The hotter the more you'll get.

It pays to sellect your leather from a hide depending on what you need it to do. The shoulders are stiffer and tend to stretch less in one direction than the other. Belly pieces will stretch mich more in all directions.

Also bear in mind, most leather bought from resellers is dressed. It's been stuffed with oils and waxes to restore those lost through the tanning process and to give it back flexibility. Ideally you want crust leathers or undressed ones. These are much less flexible and finished, but harder to get hold of unless directly through a tannery and often only in whole hides or multiples.



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Postby Colin Middleton » Mon Jan 15, 2007 1:41 pm

I've tried making boiled leather and it wasn't too hard to do. You need the water to be below boiling or you'll get G32b's quaver and you do have a minute or two to shape it before it solidifies fully. I don't know how prone it is to shattering yet (I've not done that experiment quite yet) and it does shrink lots, but it came out hard and solid. One friend even guessed that it was teracotta from the look and feel of it.

Wetting the leather will make it stiff, but I don't think it'll strengthen it much. What are you after?

Good luck

Colin


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Postby Malvoisin » Mon Jan 15, 2007 3:58 pm

I've heard that heating leather (not boiling) in bees wax will harden it but not make it brittle. Has anyone tried this?


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Postby Biro » Mon Jan 15, 2007 5:07 pm

I've tried heating in hot water, but you have to rush with the shaping and it can be tricky to get the temperature/length of time immersed right to get the correct hardness.

I've found that it's easier to soak in cold water and shape/tool there, then stick it in the oven on a low heat (grr, I wish I could remember what I used.. 150C rings a bell) to harden. This hardens it more slowly and its easier to keep checking on so it doesn't go too hard/soft. The downside is that it can be tricky getting it to keep shape - especially if its a highly curved/stretched..

Apparently its the combination of heat/wet that hardens it. If you heat it before shaping it's a race before it cools/hardens. If you shape it before heating, you have all the time in the world..

You then need to waterproof it. If it gets heavily wet again, it may lose its shape.



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Postby wat the tyler » Mon Jan 15, 2007 10:14 pm

Fantastic replies, thank you all.

I should have mentioned what it is for initially (doh). Its for the internal structure of a henin so it doesn't need to be that hard (as in armour) and so maybe just wetting it and drying it may give me the rigidity I need.


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Postby Colin Middleton » Tue Jan 16, 2007 1:51 pm

Malvoisin wrote:I've heard that heating leather (not boiling) in bees wax will harden it but not make it brittle. Has anyone tried this?


I've not tried it, but it was discussed at length on the Medieval Leather group on Yahoo. Apparently. at lower tempratures, the wax soaks into the leather, stiffening it, but only by filling the pores. At a slightly higher tempreture, the wax boils as for the water hardening and at a slightly higher temperature than that the wax catches fire. It kind of put me off experimenting.

I should have mentioned what it is for initially (doh). Its for the internal structure of a henin so it doesn't need to be that hard (as in armour) and so maybe just wetting it and drying it may give me the rigidity I need.


I'd not bother heating it for a hennin. It'll keep its shape fine and if you boil it, it could be quite uncomfortable.

I would consider putting lots of wax into it once it has dried fully though. If you rub it with wax (inside and out perhaps) until it lies on the surface and then stick it over a radiator, the wax will soak in and help stop the wearer's sweat or heavy rain make it loose its shape.

Good luck

Colin



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Postby gregory23b » Tue Jan 16, 2007 2:32 pm

Wat, have you considered felt? It may well be lighter, or some sort of cloth starched stiffening shape.

Leather is an expensive material and might involve more work than you really need to do.


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Postby Shadowcat » Tue Jan 16, 2007 3:37 pm

Buckram works for hennins and is light and will make cone shapes with no problem. As long as you bind the edges with tape/cloth/wool, it won't slip. It can be quite scratchy, so the binding helps avoid that too.

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Postby Annie the Pedlar » Wed Jan 17, 2007 10:13 am

at a slightly higher temperature than that the wax catches fire. It kind of put me off experimenting
.

Oh, I have the answer to that :)
Use a double boiler.
Half fill a big vessel (cauldron or pressure cooker?) with water. Sit it on the fire (stove or hob). Take a vessel that will sit inside the big one (a casserole, a pudding basin or an Annot and Mad Jack custom made very tall pottery thing and fill it with wax. Put the vessel with wax inside the vessel with water. Heat. The water boils at a steady temperature so your wax never gets hot enough to ignite.
Don't walk away from it though as you need to keep topping up the water or you get the "Oh my God! The Christmas Pudding!!!!!" syndrome.



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Postby WorkMonkey » Wed Jan 17, 2007 1:51 pm



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Postby Dave B » Wed Jan 17, 2007 3:04 pm

Annie the Pedlar wrote:Oh, I have the answer to that :)
Use a double boiler.


Also known as a Bain-marie if you're a cook. very usefull for melting chocolate.


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Postby polthepot » Tue Feb 27, 2007 9:53 am

Anyone tried hot olive? Idid this once with a scabbard that looked, er, to new! worked a treat, poured the hot oil into the scabbard while on knife. It shrunk a little onto the blade but was a little harder and still flexible.
Attained desired affect.


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Postby The Illustrated Man » Tue Feb 27, 2007 9:44 pm

Hot Olive... ah, she's a lovely girl, very accommodating :twisted:


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Postby George P. » Mon Dec 31, 2007 3:54 pm

Very late addition to the topic, but hopefully this will be helpful.

Boiling leather is bad-its brittle
Waxing also bad-softens in heat, makes the leather heavier, and lubricates it so it wasn't done ever for leather armour.

Has anyone tried baking? Soaking leather in room temperature water and baking at a low temperature (60 degrees) yields a lighter (the leather dehydrates in the process so its lighter than the original leather!!), stronger and less prone to cracking leather. Also, there is little shrinkage, so unlike boiled leather, it can be tooled, like the rerebrace in the British museum found in the Thames.

Hopefully someone will find this useful. If anyone is interested i can help them out with instructions.



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Postby Colin Middleton » Wed Jan 02, 2008 1:40 pm

The impression that I'd got of baking it was that you're effectively 'part boiling' the lether. Some the strands change (are they polymerising?), giving stiffness, while some don't reducing the brittleness. I've heard that over time some of the stiff strands break and flexability returns to the leather. You can re-bake it, but I suspect that it eventually gets too brittle. Also, I think that you can 'over-bake' it and end up with something more like the boiled leather.

All that said, for most applications I think that it's the approach that I'd use to harden leather.


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Postby George P. » Wed Jan 02, 2008 7:54 pm

All of the strands polymerise IF the leather is soaked properly, every bit must be equally wet. Thats why it should be left in water for at least 8 hours, then air dried (i think its called casing) enough for it to be shaped (which ever shaping method is used) then baked. Hide glue can also be used as i think most extant medieval leather armour had some form of hide glue or gesso on it. If applied properly, it can yield much stronger yet still flexible armour. However, ive found that the application of hide glue is different with different types of leather. Obviously, only vegetable tanned leather can be used, but for some reason, the exact method of tanning sometimes change the results. Ive used leather from 3 different suppliers, all 8-10 ounce leather, and have used several types of application, and all yielded different results. (to name but a few methods; 1apply hide glue while baking with a brush. 2. soaking in hide glue after baking. 3. soaking in hide glue before baking.)

I am far from an expert, all this is just things I learnt with experiance, though i was taught the basics by others.
Last edited by George P. on Thu Jan 03, 2008 6:45 pm, edited 1 time in total.



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Postby Tod » Thu Jan 03, 2008 10:06 am

I don't like giving away trade secrets but...............
Setting an oven or any thing at a particular tempreture won't work as each piece of leather is different - different animals. That's why the three different suppliers leather gave differnt results.

Boiled leather isn't, but hot water does work, and it helps to wash out any waxes or oils that might have got into it (usually from being stored next to oiled or waxed leather).

Wax will harden leather, but is has to be done right. I always use a double boiler.

Soaking leather and air drying it will not give you very hard leather, that's how shoes are made.

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Postby George P. » Thu Jan 03, 2008 1:56 pm

Tod wrote:
Soaking leather and air drying it will not give you very hard leather, that's how shoes are made.


Misunderstanding, I meant air dry only until the leather can be shaped (not all floppy like it is when completely wet.
And as to different animals, i purchased cow hide from all the suppliers. As to wax, i used to harden that way, and it really does harden the leather (probably gives the strongest armour of all methods), but i have worn it in the sun, and trust me, you dont want to get hit while wearing that in hot weather :) . Also, wax adds weight to the leather, and one might as well wear steel armour. (actually that depends on the thickness of the steel).

I would like to know how much leather is used in UK reenactment (I spend a lot of time in the Uk, but when i'm there, i generally don't have time for my hobbies, but i would love to visit some medieval festivals there in the future), and for what armour purposes, are there any rules as to thickness, authenticity and so on. What parts of the body is it most used for?

George



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Postby Tod » Thu Jan 03, 2008 11:13 pm

George P. wrote:And as to different animals, i purchased cow hide from all the suppliers.
George

Each cow, bullock or bull is different. Therefor each piece of leather is different and it depends on where on the animal it comes from, how old the animal is etc etc.



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Postby George P. » Thu Jan 03, 2008 11:48 pm

My point exactly, which is why i said i had different results with different leathers. People using the same hardening methods can get different results.



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Postby Colin Middleton » Fri Jan 04, 2008 1:47 pm

Tod wrote:Setting an oven or any thing at a particular tempreture won't work as each piece of leather is different


I'm surprised about that. I would have thought that it was a chemical change at the molecular level, which is going to be failry uniform. I expect a lot of variety in the time required for the heat and water to penetrate, dependant to the thickness and density of the leather, but I had expected the temprature to be fairly contatant.

Any tips on that?


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Postby Tod » Sun Jan 06, 2008 10:39 pm

I can't speak as a chemist only from years of experience.
To give you an idea/ This afternoon I soaked two shoe uppers prior to lasting. Both are the same in colour and thickness, but come from two different pieces of leather. Both were cut on the same direction etc etc.
One stretched enough to allow me to fix it to the last. The second stretched more than the first. The result is fine as I get this all the time.
When I harden leather I watch it very carefully. To the point I open the oven door every 5 minutes and still worry I'll cook it and it'll be rubbish.

I find that I can guess the temperature of the water I use depending on what I want to do with the end result. It took me a very long time to get it right.

So my conclusion is that I've had to learn what the leatherworkers of the past learnt as an apprentice. As an engineer I think there must be a standard way (std. temps etc) but as a craftsman I know differently. :wink:




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