A rustic look can be very attractive, but it needs to seem natural. To make a piece of furniture black and still get that rustic, natural look is possible using a variety of approaches. One method is to use tea and an iron stain together. The tea adds chemicals, called tannins, to the wood and the iron in the stain reacts with it to produce a very dark grey, brown or black stain. The exact results vary depending on the wood in your furniture, which makes your work even more unique.
Pull apart some steel wool. The finer and purer the it is, the better; you don't want steel wool with anything added to it, like oil. Put it in a jar of vinegar and let it sit overnight, letting the wool dissolve. Longer is better, and you can make the process go faster by boiling the wool in the vinegar, but this will release unpleasant fumes. The mixture should be either a light gray or a light reddish brown when it's ready; filter it through a coffee filter to get out any remaining steel wool.
Brew some very strong tea, stronger than you'd want to drink. Any kind of black tea will work. Let the tea cool. If you used tea bags, take them out and squeeze out the remaining liquid.
Place drop cloths over your work area.
Wipe down your piece with a damp rag, wait for the wood to dry, then gently sand with a fine sandpaper, no higher than a 320 grit. Don't go quite with the grain, but sand off by a couple of degrees. This is known as raising the grain and helps the surface feel smoother after applying water-based stains. Repeat the process at least once.
Brush the tea onto the furniture piece. Be generous, but don't let the tea pool anywhere. Let the tea soak into the wood. It may add some color, and this is normal. Move on to the next step when the wood is still damp, but not soaking.
Brush the steel wool solution over your furniture. Again, be generous with the amount you use. You should see a reaction start taking place quickly, changing the color of the wood. Wait for the wood to dry.
Brush on another coat of the tea if you want the stain to be even darker.
Wipe down the wood with a clean, damp cloth. Wait for it to dry.
Seal with a clear sealer to protect your work.