Muriatic acid is a strong form of acid often used to remove paint and etch pools. Muriatic acid is generally too strong for use on wood. However, under the right circumstances and with the right dilution of the acid it is possible to use muriatic acid as a stripper for wood.
Muriatic acid is a type of acid that is commonly used to strip paint from brick and concrete. Using it to strip varnishes and paint from wood is not recommended because the harsh nature of the acid can eat into the wood, causing gouges that cannot be repaired. According to studies by the State of Missouri's Department of Heath and Senior Services, muriatic acid is not compatible with wood. However, if the process is done correctly, muriatic acid can be used to strip finishes and paint from wood in extreme circumstances when nothing else is available. Always take extreme caution when working with the acid because it is equally corrosive on flesh.
The only way to use muriatic acid on wood is to water it down and use it quickly. Dilute any muriatic acid solution to 10 percent strength. In other words, mix one part acid with nine parts water. Have a bucket of rinsing water on hand before using the acid. Dip a brush into the acid solution and rub onto the surface of the wood. The finish should immediately start eating away. Immediately after brushing on the acid coat take a wet cloth and rub the remaining acid away. The finish should come up along with the acid. When fast actions are taken in this method then, and only then, is it safe to use muriatic acid on wood. If the acid seems to have no effect at all at that strength, then gradually increase the concentration of acid until you get the desired results.
Muriatic acid is also used for the conservation of wood. This is only recommended for hardwoods such as oak, cherry or maple. Softer woods cannot handle the acidity of muriatic acid. Once the wood has been washed it can be placed in a bath of muriatic acid made of one part acid and nine parts water. The wood should soak for two to four days in this solution. The wood should then be rinsed for an additional three to five days--under a running water stream, for example--to eliminate all traces of the acid. This treatment can help prepare the surface to receive new resins and varnishes.