Recently, I was able to begin working in a traditional blacksmith's shop on one of California's state parks, and part of the involvement as a demonstrator/educator means I must also wear traditional ~1860s era clothing. Since there are a good many tools which I transport to and from the shop, I decided to make a leather toolbag. Cut and stitched from a single half hide of leather with forged buckles, the bag promised a great deal of use but needed a bit of treatment and preservation from the unstained vegetable tanned hide which it came from.
To begin, I made a vinegaroon solution. In essence, it is an acidic ferrous solution which reacts with the tannins in the leather. In addition to leather, a variety of other materials react with a similar darkening when exposed to the iron, including several species of hardwood. This solution turns the leather from its normal tan brown to a dark grey/blue and then black.
Making vinegaroon is extremely easy in its simplest form. I took a handful of metal dust from the belt sander and poured white vinegar over it. As the iron dissolves into the vinegar, it forms what I later used. Shavings from a file or steel wool, anything iron or non-stainless steel with a good amount of surface area will work.
For around three days, the vinegar-iron solution sat on the counter and worked its breakdown of the metal dust. A funky skin began to form on the surface of the vinegar as a result of the oxidation and lifting out of impurities trapped in the metal dust, likely wood and abrasive particulate. That scum was skimmed off the top and disposed of. Once no more of the metal dissolved in the vinegar, it was time to strain the mixture. This is not the first vinegaroon I have made, but it was by far the strongest. I suspect that the more saturated the solution, the stronger it acts. Diluting it with additional vinegar would have left the leather surface a paler blue grey rather than the dark black it ultimately became.
Trying to use a coffee filter to strain the mix, the progress was so slow that I eventually gave up on that and used a sponge to absorb the liquid, leaving at the bottom of the original container a layer of particulate at the bottom where the metal and other stuff did not dissolve or rise to the surface.
In the end, I was left with a good amount of vinegaroon. The liquid is not very turbid and should not separate after sitting for a time.
Here is the bag after constructing it, before applying the vinegaroon. I would recommend that, in most leatherworking endeavours, that the entire surface be treated (or at the least dyed) before assembly. Since I did not have a pattern or template or really even a general design idea before beginning the stitching, I decided not to treat it until after I was finished. As a result, the deeper cracks of seams are unfinished and present a slight feel of mediocrity to the approach, but there is nothing I can do about it now.
To apply the vinegaroon, I usually use a cutting of sponge. Rags will probably work just as well if not better for large uninterrupted pieces, but I find that this does a banger job at getting into tight spaces.
Almost immediately after contact with the vinegaroon, the tannins react and the leather stains black. That small patch was one quick wipe, the photo taken only a second or two after application.
After one coat, the surface is fairly representative of the final shade. I went back for a second pass to even out any spots and catch places I may not have gotten thoroughly the first time, and addressing the hard to reach seams. It did manage to darken the shade just slightly, but the deeper black colour comes later when the surface is treated with oils and wax.
Because the process is chemical and not merely the absorption of stain or dye, the leather's colour is a bit more durable and better able to highlight the natural grain. And it is a simple process that does not require anything dangerous, is easy to do, and could have been done for hundreds of years to the same effect.
Now that the leather is dyed, it's onto the preservation side. For this project, I modified a recipe I came up with a while back in the effort of making the treatment a little easier to apply. Before, there was so much wax in the mixture that it was too solid at room temperature to apply. For this round, I used a mixture of
-Neatsfoot Oil
-Olive Oil
-Beeswax
The actual proportions varied a bit, but trying to compensate for the beeswax as it solidifies. Really it's trial and error to get the consistency you want. In the end I had something like 75% oil : 25% wax.
Rigging up a little double boiler, I started by melting the wax. This took a little while, so in the meantime, I began the process by giving the entire surface a coat of the neatsfoot oil.
Wiped on with a rag, the oil absorbed fairly quickly into the leather, which is what I am after. Having that deeper oil penetration will help later with it drying out and becoming brittle. Since the wax is a bit more solid, it tends to remain closer to the surface and keeps the intermixed oils there with it. Also, you can see that even that little bit of neatsfoot oil significantly darkens the shade left by the vinegaroon.
Once that oil was applied, the wax melted and I was able to mix in the olive and neatsfoot oil. While it was still hot, I gave everything as many coats as I could without having a visible waxy accumulation. Had I a heat gun, I would have used that to help the leather absorb the mixture better. Even still, the hot mixture went on easily and with a bit of buffing resulted in a reasonably effective surface penetration.
That's about all I did to treat the leather for the time being. When I see it beginning to show signs of wear or dryness, I will go back with the oil/wax mixture and seal it up again. With the wax, the leather tends to have a decent moisture barrier, and from the oil it stays supple. Together, they give a naturally durable surface that will hopefully withstand the abuse of a 150 year old shop.
