Friends,
As an old former college chemistry major I question the propriety of using cloth fabric dyes for staining a wooden rifle stock. All coloring agents are NOT the same and their chemistry determines their behavior.
The acid-iron stains such as "aqua fortis" and vinegaroon rely on a solution of iron ions and acid ions in water. Since wood is typically around 8% water, by weight, a water-based stain allows the iron ions to flow into the wood where they bind to the individual cellulose fiber molecules. Adding a little dish detergent or isopropanol will reduce the surface tension of the water-based stain solution and facilitate deeper penetration into the wood. When the stain dries vinegaroon merely allows the acetic acid to evaporate and aqua-fortis stain requires heat of about 300F to vaporize the nitric acid. This leaves the iron ions in the wood. They combine with the oxygen in the air and form iron oxides. The iron oxides impart the reddish-brown to blackish brown color to the wood, based upon the relative concentrations of ferric oxide versus ferrosoferric oxide. These are stable inorganic compounds that will remain as is for centuries.
Most of the commercial stains we can bye are comprised of iron oxides ground-up into a fine powder and suspended in a liquid vehicle. The finer the oxides are ground-up the better the stain but also the more expensive the stain. When the stain is applied the ground-up solid oxide particles stick to the surface of the wood fibers. But since the iron particles are suspended solids in a liquid vehicle they cannot penetrate as deeply as and individual ion - they are approximately 10,000 times larger in diameter. The end result is a stock with the right color but the appearance might not have the depth of color and the light reflection characteristics, called chatoyance by artists, of an acid-iron stain. But, some think they are easier to use. Sometimes easier is better, sometimes not.
Then we get to dyes. Dyes are organic compounds that use the molecular structure to reflect selected colors if incident light and absorb the rest. Since dyes are a mixture of dissolved molecules in a solvent vehicle they have a similar ability to penetrate more deeply into the wood, like an acid-iron stain, BUT the dye molecules are subject to chemical reactions over time, temperature, humidity variations. Consequently, dyes tend to fade. Compare a new pair of blue jeans with a pair you have been wearing for a year. If your objective is to produce a product that has a short usable life-time then dyes are a suitable coloring strategy. If your objective is to have a product that will serve for many years it might not be the best. Dyes are easy to use. But is easier better?
Best Regards,
JMC
