View Full Version : How to "Harden" Leather

Chuck Burrows
11-05-2002, 10:58 PM
The following method of a hardening leather is not my invention. The basic method has been in continuous use for several thousand years. I have studied the subject extensively and the following method is based on what bonafide experts say. I have heard of some people dipping the leather in acetone instead of wetting it with water, but I don't like using that stuff unless absolutely necessary. NOTE: I have a liver disease (NASH-level 2) and the doctor's figure that at least in part it is from having breathed and absorbed so many toxic fumes over the years and no I was never a heavy boozer but I am now forced to be a teetotaller. So be careful with that stuff!

The process was known as cuir boulli (boiled leather) in the Middle Ages, but they NEVER actually boiled the leather. (I've tried it - it will totally ruin your leather - TOO HOT - the leather will shrivel up into a tight ball). The process is still used commercially to make cigar cases and such - it was never a "lost" art.

1) "Case" your leather to moldability. The outside aka smooth side of the leather must have no dye or finish on it at this point (if you're doing a pouch type sheath it's OK to finish the inside first and then sew it). To case my leather I thoroughly dampen the sheath or whatever, put it in a plastic bag, and leave it over night in the refrigerator. You want it damp not soaking. It is properly "cased" or "sammed" when the color is almost the same color as a dry piece, but it will feel "cool" to the touch and act like semi-stiff putty. This is the same state you bring it to when tooling it.
2) Mold and bone it to shape if this is desired, but don't let it get too dried out. You can remoisten it by wrapping in lightly dampened towel and putting it back in the plastic bag for a while.
3) Here is the process that makes leather hard - semi-rapid dehydration from the damp state. Dry your item between 120-160 deg F. I use a thermostatically controlled food dehydrator for this but you can also do it by making a 2-3' square wooden box and setting a hot plate in it or set it up with a couple of light sockets with 100 watt bulbs. Use an oven thermometer and make a little sliding door so you can control the heat. A small fan to move the air around inside the box will help. Suspend the leather so the hot air can move around all sides. You need to experiment with temperature and the wetness of your leather until you get the hang of it. The thickness of your leather determines a lot as well - thinner leather dries faster and can wrinkle or shrivel very easily. I'd recommend 5-7oz vegtan for small sheaths and 8/9 oz for larger ones.
KEEP AN EYE ON IT! Too hot and the leather will either shrivel up or turn out so hard that it will crack. Too low and it won't get hard enough (you can always re-wet and re-dry). I've found best success at around 130F for good stiffeness. You can also dip it into a pot of 160-180F water and then put it in your drying box. EXPERIMENT WITH SCRAP if you do this one. This will make it dry faster and harder. I don't find it necessary.
4) Leather dye will also stiffen leather to a degree as it dries it out chemically. If you're going to dye do it after the above process. I then use first a light coat or two of Lexol Conditioner and then a water resistant top coat of something like Fiebings Leather Balm or Tan Kote or even Watco Danish Oil. I don't recommend using the beeswax/oil bath as that amount of oil may actually soften it, but feel free to try. I have read of some fragmentary accounts of how they did use pure melted beeswax or a mixture of beeswax and pitch to waterproof it (Leather drinking Jacks and Bots were lined with brewer's pitch to make them watertight with cold liquids). With larger pieces such as breastplates they sometimes glued in fine woven linen or canvas linings.

I've made leather armour out of 10/11oz using this method that will turn a sharp sword stroke when properly padded underneath.

One caveat: this is always a touch and go process - every hide is different even in the same weights.


11-07-2002, 08:24 PM
this is great info, chuck. thanx for taking your time to post it. i do have one question, though, re:
I don't recommend using the beeswax/oil bath as that amount of oil may actually soften it,
is there a mix of these other than 50/50 that you would recommend? seems this is the generally accepted way to go for weather proofing.

Chuck Burrows
11-07-2002, 09:09 PM
To weatherproof I use the top coats as listed above and then for a real good weather proofing I use Obenaufs Heavy Duty LP( I worked as a logger up in NW Washington (where everything gets WET) many moons ago and used this stuff and found nothing better for keeping my feet dry. It's a beeswax based product.
I also use Mt Pitchblend ( which is a mixture of Beeswax, Mink Oil, and Pine Pitch. Since it has oil you have to be more careful but as long as you don't saturate the leather it works great ( this is what I use instead of the wax/oil bath - just warm the leather up and rub it on!)

Hope this helps.

Jason Cutter
11-26-2002, 10:08 PM
Chuck, great information.

Strangely, I've been using portions of the same technique to do my moulded sheaths. I discovered them purely by accident and was realyl pleased with the result. I'm referring to the hot not boiling water, semi-rapid drying from half-damp. Took me 1 year to figure it out. Just goes to show you should ask around before wasting time doing it all by trial and error and wasting heaps of leather. But honestly, thats half the fun, really.

Good warning about the acetone - I previously used it because I was too impatient waiting for water to dry. Just as well I've developed some patience - could be saving some bodyparts.

For weatherproofing, I got a product imported by Australian KNifemakers Supplies called EKOL leather lacquer, which looks water-based and when dry stiffens and actually very effectively waterproofs the leather. Seems to work although I'd love any info you have on this stuff. Before using that, I'd been using the hot oil method and my sheaths all looked like sopping oilly masses.


Chuck Burrows
11-27-2002, 11:12 PM
That is what I call re-inventing the wheel and yes I have done it many times and then went OH! somebody already knew how to do this! A few hours research (and the Internet has made that immensely easier) can save many, many hours and dollars.

Don't know anything about the Ekol and when I did a search the only thing that came up was the Australian Knifemakers Supplies site. Does it give ingredients? It sounds like it may be similar to Neat-Lac, a leather lacquer finish sold by Tandy's amongst others. I know Neat-Lac is always a bear to take off when re-finishing a piece.

I've also used thinned down wood finishes on hardened leather and they seam to work great.


11-28-2002, 05:43 AM
Some time back, a fellow told me about this Jaguar product called "Hide Care." Not supposed to shrink, stretch or discolor and be completely waterproof. Plus it's all natural.


I tried it on my riding leathers and it works a charm, everytime.
Used it on a couple of sheaths, has held up very well- so far.

Available through any Jaguar dealer. Pricey but quick.

Chuck Burrows
11-28-2002, 08:11 AM
Now if I still had my old Mark II.....

Sounds like neat stuff. No Jag dealer in Durango though. Maybe on the Net.

Thanks for the info. I'm always interested in good leather care products.


Jason Cutter
11-28-2002, 05:15 PM
Chuck, the Ekol leather lacquer may be the same thing as the Neat-Lac. Yes, the Ekol stuff is also pretty darn hard to get off when refinishing something. Its also quite difficult to get off the old fingers when its completely dry - worse that trying to remove epoxy.

This might be off the point now, but one word of warning. The lacquer seems to penetrate well enough that it can cause the layers of an overlay to delaminate while it is wet, so the overlay needs to be stuck down real well.

Also, I've found another advantage to thoroughly wetting and "washing" the leather is that it removes any unwanted chemicals, dyes that might damage the steel later on. Its very hard to get vegetable tanned leather where I live and a lot of the commercial leather suppliers only have chemical-tanned skins. After doing the whole washing thing, there's been nary a problem with tarnishing, pitting of carbon steels even if the knife has been accidentally left in the sheath for prolonged periods.

Thought I'd pass that one on.


12-26-2003, 11:59 AM
okay,,,,i read how you make the leather sheath hard,,,and some of what you have posted seems to be way way different than what I have been doing...

so I need advice for my system, and what you guess my system for leather treatments will do to my sheaths in the long term...

what I do is make the pouch sheath , my sheath is the very same design that Ed Fowler has, infact it was Ed who sent me many emails on how to cut and stitch the sheath.

But, once I am finished with the sheath, I dunk it in a hot wax/bees wax/mink oil, bath.

The bath is in a doubble boil pan with water under the top pan, I heat the bath up to the point where all the wax and stuff is runny..I have gloves on so I can hold the leather in the hot wax/oil bath for a long time, turning the sheath in the bath and filling it and dumping it out over and over.

when the leather is real soft, I place the plastic-wrapped knife into the sheath a few times, forming the mouth of the sheath to be wide enough for the kinfe to fit into it.

I hang the sheath with the knife still inside it untill it cools and is hard.

about every 15 min I test the sheath's fit on the blade, pulling the blade in and out a few times.

The next morning the sheath is ROCK HARD,,and the knife now will make a cool Poping sound when you take it out or place it back into the sheath.

QUESTION,,,,so far I like the way the leather both looks and feels, but in the long term, will my system need to change?

(The reason this is an important question for me is that Im now in the middle of posting a toturial on how to make a sheath, The last thing I will post here will be on the topic of harding the sheath,,,I need to make sure that while my system might be a bit different than others, that it WILL NOT cause a long term harm to a sheath)

01-21-2004, 02:50 PM
There are some really excellent waterproofing mixtures made by NIKWAX for use with hiking gear that would probably work well for sheaths.

They are was based with a water carrier to help protect the leather from chemical damage and limit softening. I have had good success using them on my hiking boots. One pair in particular have stood up to about 6 years use after only two applications of the Nikwax about 2 weeks apart.

06-20-2004, 02:10 PM
Here's a 05/26 post by A.T. Barr:
Hardening Leather
I got this link from the Leather Guild.

Way more information than I need.


"Don't you buy no ugly knife"

Brett Holmes
09-05-2006, 11:19 PM
i have a sheath that needs hardening but it has already been dyed, any sugestions??

09-06-2006, 08:11 AM

It won't make any difference if the sheath is already dyed. All of mine are dyed before assembly and hardening. I seal the inside before stitching and then harden. When it's good and dried, I seal the outside and rub out the finish. I use a food dehydrater to do the hardening. It's safe and works well. I have forgotten (maybe one to many bourbans) and left a sheath in all night long with no bad results. Can't do that in the oven. Good luck!

Chuck Burrows
09-06-2006, 09:23 AM
What Rick said - and remember the leather SHOULD NOT be sopping wet - just damp.....

Brett Holmes
09-06-2006, 07:14 PM
cool, thanks guys.
unfortunately im now thinking i will have to throw this sheath ot :( one mistake and all that effort down the tubes.

05-01-2007, 10:08 AM
I've got leather "wood" hard just by hitting it with a few layers of dye and hairdrying it quick. It's not usually a quality I am looking for in my finished work, but I can see a definite purpose in it for certain things.

07-21-2007, 08:16 AM
I live just down the road from a John Roberts who is a "master" (my term) leather worker with a number of high profile commissions to his name.

He explained to me his method for hardening his signature Fire Buckets, Gargoussiers, and Cartridge Cases as seen in the movie "Master and Commander" w/ Russel Crow.

He employs the "cuir bouilli" process as described previously, but he bakes the finished piece in a standard electric oven at 120 degrees F. for approx 1-1 1/2 hrs (depending on thickness and design until the leather is bone-dry and VERY hard. I have seen his pitch-treated buckets at Fortress Louisbourg used to hold water and they are indeed rock-hard.... for ever. This is the process I used to harden the sheath in this thread:

CJS Knives
11-20-2010, 06:40 PM
good info guys thanks!

12-12-2011, 02:14 AM
Thanks for sharing such informative post.

12-12-2011, 02:44 PM
Alchol dyes when drying harden the leather somewhat but for best results I use a food dehydrator which is right around 120 degrees and like 20$ from walmart plus no wife yelling at me for taking the oven up again

01-29-2013, 08:18 AM
i use a product called snowseal put it on the warm leather after dying lasts and lasts. i do all my work boots and shoes as well as sheathes tomsons waterseal works also but will sofen leather if you use too much light coats work well :rolleyes:

02-14-2014, 08:27 AM
Wow your description is really detailed! Working leather is not easy at all...I will certainly try your method! Thank you..

07-21-2014, 07:30 AM
Thanks for sharing this info with us chuck... information like this really comes in handy

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