I love control. Been accused of being a bit of a freak about it.....more than once.
For me, it has everything to do with outcome. When you're talking about that kind of behavior as it relates to people, well let's just say that's a bad thing but if you are talking about craft, that's a whole 'nother kettle of fish.
This is the part where I voice my frustration about aniline dye. I've been using aniline dye for 30 years and like any relationship it's had it's ups and downs. The good ones have more ups than downs and I can say with all certainty that aniline and I fall squarely in the downs column. Remember the control issue I have, well aniline is a wild horse that can't be tamed. She NEEDS her freedom, to run with the wolves, to not be tied down. And man, was she an unpredictable slob. I knew we couldn't go on like this so I decided to leave her but I knew that I just couldn't up and walk out, I would need a plan.
I had read about vinegar and iron dyeing a while back and was intrigued; a process that would create a chemical reaction by binding an iron ion (yes, I know that this is a simplification) to the natural occurring tannin in leather. This was not really a dye but a reaction that created a color by combining an outside source with an inside one. The only variable being the amount of tannin in the material (which could be amended by the soaking the material in something tannin rich, like black tea). It was non-toxic, inexpensive and repeatable. Sign me up.
But alas, for whatever reason, there was very little reliable information on how to make it.
There is speculation that Vinegar and Iron dyeing was discovered by ancient Egyptians but what is for sure is that this process has been used for centuries by leatherworkers in various forms. I'm not sure why a standard recipe doesn't exist. Perhaps it's because each leatherworker considered their version a trade secret. Maybe it fell out of favor once aniline arrived. Who knows. Either way, there is very little helpful information on the web. Mostly it's of the "throw some rusty nails in vinegar and wait a month" variety. Not what a self identified control freak wants to hear.
So I decided to take everything I could find on the subject, parse it, make some guesses and do some control experimentation. I couldn't be happier with the results.
1 gallon of White Distilled Vinegar (5% acidity)
4 pads of 0000 steel wool
Large Sauce Pan
Pour one gallon of the white vinegar into the sauce pan and heat to a pre-boil. (I would advise doing this outside).
Let the hot vinegar cool enough so as not to melt the plastic jug you will be pouring it back into.
While the vinegar is heating, unfold the steel wool pads and tear the steel wool into 1" wide strips.
Place the strips into the empty jug.
Pour the heated mixture into the now steel wool filled jug.
Leave the cap off and place the mixture somewhere that is room temperature.
Using a chopstick, push the steel wool down to the bottom of the jug. You are trying to eliminate as much oxygen and steel contact as you can so do this daily. Do not shake or vigorously stir the mixture, remember - oxygen bad.
For best results, allow the mixture to sit for at least 2 weeks (I wait 3 weeks).
You now have your mixture ready and the big day has come to dye some pieces but wait....there's more. You will also need to neutralize the acidic content of the mixture as it will degrade your leather and make it brittle over time. I use a baking soda and water bath to do this.
Here's how I go about it:
I have two sheet pans, one for the mixture and one for the neutralizer. The leather goes into the mixture sheet pan and sits for a couple of minutes. I then take each piece out and expose it to air for 5 minutes (this is when the color change actually takes place).
I then place each piece into the second sheet pan with the baking soda and water mixture. I use the scientific measurement of two fistfuls of Baking Soda into the sheet pan full of water. The pieces only sit in the neutralizing bath for about 30 seconds.
Next, I rinse each piece in water.
I then place the pieces on a drying rack for a day or two.
What you will get is a Blue/Purple black. To make my piece deep black I apply Neetsfoot oil to each piece. This gives it a rich and dark black and eliminates the blue/purple. Finally, I apply a Beeswax and natural oil finish and buff.
That's it. I have control over the results and I couldn't be happier. I can do small batch dying with minimal fuss and mess. And I get the same results every time.