To make the mixture is fairly simple - I use plain household vinegar and fill a regular size jar with it. I then add some scraps of metal. Since I use steel wool fairly frequently as part of the finishing process, I generally throw in a few pieces to the mixture. After a day or so, the mixture has generally fermented enough to try out. (By the way, the process doesn;'t generate much gas, but to be on the safe side, I leave the lid fairly loose.)
The fun part is to take a paint brush and "paint" the piece of wood you're interested in. At first it seems as if you're painting with water, but fairly rapidly the surface darkens according to the tannins in the wood. Olivewood, which I frequently use, has a great deal of tannins and turns almost entirely black-brown. Each wood reactsdifferently so each time you intend to use the mix, you have to check it out on a scrap from the piece you're working on. What's nice about the whole process is that there is reaction underway within the fibers of the wood; it's not a layer of synthetic material on top of the wood surface. The result is a really nice natural finish. And if you're not happy with it, it can easily be sanded away.
There's a lot more information on the internet, but I think I've covered most of the main points. When you do get around to trying the process I'd be interested in hearing how things worked out. All the best.
