Analyzing aniline dye problems

Understanding the complexities of aniline dyes and their application. October 9, 2002

I am using aniline dye for the first time and not having a lot of luck. It's an oil-soluble aniline, so I was using naptha as the dissolvent. It went on okay, but when I wiped it off, the color looked very streaky and uneven. It's on birch ply and poplar. Next, I used a rub-on poly. I put it on with a foam brush and then wiped it off. I did this to the inside of the box and it seemed to even the color out. Now I just did the same thing to the outside and it seemed like the poly was taking a lot of the color off. What am I doing wrong? I am using an ebony color on the aniline dye. I don't know if I want to use aniline dyes anymore.

Forum Responses
Using aniline dyes successfully requires greater understanding of chemical properties, application techniques and finish compatibilities than using the common "over the counter" pigmented (or combination pigment/dye) oil stains, such as Minwax. The simple reason for this is that most store-bought stains contain one additional ingredient that makes them "homeowner" friendly - a binder. Once the carrier (usually mineral spirits or other slow evaporative chemical) evaporates, the binder pulls everything (dyes and pigments) together and sticks it all to the surface. Once completely dry, it is not readily dissolved back into solution when (even) the same type of finish is applied over it. This is why you can apply an oil-based paint (oil poly) over the top of a dried pigmented oil based stain (Minwax for example) without having the problems you are encountering.

Dye stains contain no such binder. They only contain what you put in them. When you create the stain, you add the type of carrier that the stain is designed to be soluble in. Unless you then add the mixture to a compatible finish, you will be left with only the original dye power in and on the wood surface once the carrier dries. Put any one of the solutions (that the dye is meant to be soluble in) on top of that dye and the dye comes back into solution.

Was the rub-on poly oil-based? If so, your oil soluble dye is being brought back into solution when you put on the oil poly and when you move it around by rubbing it, you will transfer the dye to your applicator and remove some (or much) of the color. Keep in mind that your oil dye is also soluble in mineral spirits, the common carrier/thinner in oil poly.

To use aniline dyes properly, you must think through your finish schedule and application method and choose the proper components and methods to insure compatibility. In order to be compatible, you often have to think "incompatible". Sounds confusing, huh? If you want to apply an aniline stain to the wood and then brush or rub over it with a finish, you need to use a finish that is incompatible with the type of stain you are using and then remove ALL the powder that is left on the surface after the carrier dries.

Spray finishers can often get over this obstacle by shooting a dry coat or two over a compatible dye stain because they are in effect, binding (or sealing) the stain to the wood under the dry coats. Too heavy a coat will give the dye a chance to dissolve into solution and bring it right to the top where it will again mix into subsequent heavy coats.

Welcome to aniline dyes. Keep trying and remember “incompatibility” is what often makes these stains “compatible”.

I almost forgot your first problem. If you are going to use an oil dye applied and wiped off by hand, it's best to use mineral spirits, a much slower evaporative solution to give you time to spread and even out the color, thereby eliminating streaking. A water dye stain would have been better for this application even though grain raising is brought into the equation.

I would switch to a water based aniline dye. Oil dyes are not light-fast at all, in my experience. Try the Transtints - I think you'll be much happier, now and in the future.

We use aniline dyes mixed in water, sprayed on, wiped off and left to dry, and spray water-base topcoat over the dye, and have no problems. We no longer use oil-base products after using the aniline dyes and would never go back.

Are you spraying the dyes? If not, then stay with Minwax.

Spraying is ideal but if you don't have the equipment, you may want to try lightly brushing on a couple of "wash coats" of thinned shellac over your dye before going to the finish coat. The shellac will help seal the surface over the dye and reduce the amount of color the finish coat takes off. When you have dried dye powder sitting on the surface, any brushed-on wet coat, regardless of its solvent base, is going to pick up some of the dye. The shellac will do this as well, so you may want to make your original color just a bit darker to begin with. I agree that you'll have much better results with water based dyes.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor W:
I would suggest trying to wipe the wood with a damp cloth with distilled water to raise the wood fibers, then lightly sand to smooth the wood. Then use your water base dye and the wood fibers will not raise back up, making it smoother for your coat of sealer. Using un-distilled water may add minerals that darken or stain some wood fibers - especially red oak.