A simple-to-create mixture produces beautiful gray to black finishes.

These four samples, all on oak, show various effects obtained by using shop-made acetic acid stains.

If you ever have a woodworking project that needs to be stained in the color range of a light barnyard silver gray to a deep, dark black, you may want to try making your own home-made dye stains. In this column, I want to describe an old, tried-and-true method that you can use to make up your own chemical acid stains to achieve those hues.

Start with a clean quart-size glass or plastic container. Then, add a couple of unfolded steel wool pads, some old rusty nails and old metal screws that you have laying around the shop. Pour in some common 5% household vinegar to fill three-quarters of the jar. Then, cover the container with a piece of cardboard or wood and let it ferment.

(Note: As a precaution, never use the jar’s cover unless you vent it with some holes, since you can get a buildup of expanded gas in the container, or so I have heard. Also, whenever you work with chemicals like this, be sure to wear personal protective gear before you do any mixing.)

The more iron content in each of the items that are added to the jar, the faster the color will develop. I allow several hours to pass, so that the acid in the vinegar and the iron content in the metals can react with one another. After that, you can do a test on some scrap wood to see how the color is developing.

You also should be aware that there are some steel wools which have a light protective coating of oil that is added to prevent the steel wool from rusting. When this type of pad is soaked in vinegar, it slows down the process. But it will dilute and then dissolve the oil, so in time, the acid will begin working and increase the speed of oxidizing the iron contents in the steel wool.

Generally, you will not get good color while the chemical transformation is first taking place. It is important to check your “home brew” frequently for color. You should leave some pieces of the actual species that you will be staining near the jar. Thoroughly mix the acid solution before you test for color in order to get a uniform stain. I suggest using either metal acid brushes or disposable cotton swabs to do the color testing on your sample.

Once you achieve your desired color, you should stop the aging process of the home-brewed acid stain by pouring the liquid into a clean jar. The liquid should be transferred through a paint strainer, coffee filter or cheesecloth to remove any impurities. If your color becomes too strong from the iron content, you can add some water or clean vinegar to dilute the color strength.

These three panels show, from left, Baltic birch, oak and walnut, in their natural colors (top) and ebonized with an acid stain.

These four panels show woods treated first with tannin tea solution, then after the application of an ebony stain and clearcoats. The species are, from left: burr oak, red oak, spalted maple and walnut.

You will find that certain woods take the stain better than others; species such as oak, walnut and mahogany, which are very high in natural tannin, work the best with this type of acid stain. With species that contain little tannin, you may get some shades of greenish browns and yellows. To darken such woods, you can add your own tannin — dissolve some tea leaves or a few tea bags in clean hot water, then brush the tannin solution onto the wood. You will get darker colors, however, they may be in the brown family, depending on the wood’s natural color. I strongly suggest that you do complete testing on samples if you decide to add tannin to your wood.

Learning through practice
To really become comfortable with the acid stain aging process, keep notes from the day you start and keep testing the stain on a piece of the same wood that you want to color. Write the date next to the stain on the wood sample, so you know how long it will take to get that same color next time. In your notes, describe the color for yourself, in case you want to duplicate that color in the future. Remember, always stir the mixture before you do each color test, as well as when you are staining an actual project.

Through testing, you will learn how many hours or days it takes to first get to light silver gray and then to dark black. You also will learn from using the quart container how much stain you will need to do different size jobs or whether a larger container will be required to make up more stain for larger pieces.

I recommend that you stain your work as soon as possible after you make up the stain and that you make only whatever stain you need for each job. When making stains, I personally prefer going to the darkest color and then lightening it by diluting the stain with vinegar or water.

When you are ready to use this stain on an actual project and have selected the color you want, make up a complete fresh sample. Start with wood that is clean, well sanded and free from dust or any other residue. Then wipe or brush on the stain. If you are brushing, use a foam sponge brush or a synthetic bristle brush and be sure to cover the entire surface.

If your completed sample indicates that on the species being used, the liquid stain might raise the wood’s fiber, then on the actual project you should first sponge down the wood with clean water to raise the fibers, when the wood dries. Then, when the wood dries, you can sand down the fibers and proceed with your acid staining. Always allow the stain to dry completely before you start applying your clear coats to protect the finish.

Making complete samples can be a valuable tool. First, it enables you to learn the process first-hand; second, if you do run into a problem, you can correct it before you attempt doing it on an actual project work; and third, it allows you to find out whether all your materials are compatible with each other before you have a problem.
After you learn this entire process, you may enjoy having this chemical staining technique in your bag of finishing tricks. e

Mac Simmons is a freelance writer and 50-year veteran of the furniture finishing, refinishing and restoration trades. Mac has written articles for woodworking magazines in the U.S. and in the UK, Austria and Canada. Questions may be directed to him in writing c/o CWB, 400 Knightsbridge Pkwy., Lincolnshire, IL 60069 or via e-mail c/o [email protected].