No contest, dyes win hands down, why? Clarity, clarity and more clarity. Stains are nothing more than pigment, think thinned down house paint. Stains contain pigment, a binder to help hold it in solution, and a carrier to make it easier to spread on the surface. The darker the color, the less of the grain you will be able to read because of more pigment. I do use stains ( I make my own) if I'm trying to match something and I can tell that it was originally stained. Dyes, used to made from aniline (a coal tar derivative) but no longer are. Many people still refer to dyes as aniline, but since around 1865, synthetic dyes were developed that no longer contain aniline. Dyes can be water-based, alcohol or acetone based, or oil-based. Some will be ready made like "Mohawk" and others will be powders like "Arti"
"Arti" which is short for "Articol," are a powder that is soluble only into water. I almost always use distilled water that I put into an electric tea kettle (available at "Target"); heat the water until it is hot, not boiling, then measure out the dye (I use plastic measuring spoons) and slowly add the dye to the water (use plastic measuring cups) until it is completely dissolved. It is also important, to let the dye cool down to room temperature before applying to the surface. Next, strain the solution through a cone strainer or coffee filter, or if you want to live dangerously, your wife's panty hose! If you don't strain the dye, you might have a particle or two that didn't hit the waterand you may get a streak of color, not good. These dyes can be brushed onto the surface, or sprayed or even wiped on. The biggest thing with water based dyes are that since water is the carrier, in hot weather, it is harder to keep a wet edge. Almost all dye companies will make say an oak or walnut dye and they will vary in color from company to company just like paint does from manufacturer to manufacturer. Choose a dye company and become familiar with what their dyes colors look like.
So a water-based dye like "Arti" has only two things the dye powder and the carrier, in this case water. Once the dye powder has dissolved into the water, it will not settle to the bottom like stains will do. Pigments (in stains) are just suspended in the carrier, so you must stir constantly to keep them in suspension, unlike dyes. Salt or sugar dissolves into hot water correct? Dyes are just the same. Dyes, will penetrate deeper into the surface than pigment. The size of a dye particle would be like comparing the tip of a pin to a boulder. Pigments lodge themselves into the largest pores on the surface whereas dyes, being so tiny in comparison will penetrate deeply and with more transparency. So, are dyes suitable for exterior work? Not really, they will fade quickly, this is where stains (pigment) tend to work better, since they will help diffuse the ultra-violet rays of the sun.
There is another manufacture of dyes that you may have seen at "Rockier" or "Woodcraft" called "Transtint" These dyes are soluble into water, alcohol, lacquer thinner or acetone. What I'm finishing will determine which type of solvent I will dissolve the dye into. When using water as the carrier, with these types of dyes (being liquid) there is no need to heat the water, as they will dissolve into water at room temperature or even cold water. When using any water based dye, I typically will pre raise the grain with clean distilled water. Why you may ask would I do this? Water will cause the wood fibers to swell correct? Yes, correct. If I pre raise the grain with clean water first, the dye won't tend to raise the grain nearly as much. After applying the dye and the water has completely evaporated, you may have the thought of sanding the surface smooth, do not do this as, you run the risk of sanding through the color back to bare wood. Wait until after the 1st coat of finish has been applied, if it is indeed a membrane finish and not an oil of finish of some type. One of the many benefits of dyes vs. stains is clarity, but since dyes have no binder in them like stains, once dry a second application can be applied and darken the color if you need to. Secondly, dyes can be reversed by washing the surface with household bleach if you don't like the color at all. I often use the "Transtint" dyes for doing touch up work. Let's say for example that I have dyes a piece of wood using the "Transtint" dye, and there is a sap streak running through my piece. I can make a second color using the dyes to correct the light sap streak.
NGR Dyes, are non-grain raising dyes, hence the name NGR. If you take an equal part of denatured alcohol and acetone, dissolve the "Transtint" dye into these two solvents you have now made an NGR dye. Since these solvents dry so quickly, they really need to be spray applied to control the color so you don't get streaking. I like using dyes like these when I don't want to raise the grain, and am in a hurry to get something finished. These types of dyes are useful especially when applying color to say turned pieces since so much of it is end grain, which is so porous. Another benefit to using say "Transtint" dyes is that since they are soluble into alcohol or acetone, I can add them to shellac or lacquer to adjust my color. Let's say for example I've dyed my project and the color is slightly too red and I'm using a spray applied clear lacquer as my finish. I could add some green "Transtint" dye, which is the opposite of red, spray apply the first coat of lacquer with this tinted finish and make my color slightly browner negating the reddish cast to it without stripping and undoing what I've already done. Since the dye has clarity, you will still read the grain very visibly, just without the reddish cast.
Oil Soluble Dyes, are often used in pre-made stains like some of the "Minwax" colors, say for instance dark walnut. The way to tell if it is an oil soluble dye or a pigmented stain, put a stir stick into it, if there is clumping at the bottom, this is pigment that has settled at the bottom. Dye stains won't have this characteristic. Now just to confuse the situation, sometimes these pre made stains can be both a dye and a pigment combined. Will the company tell you this? No they tend not to give much information at all making it all the more confusing. So how do you tell if a ready made stain is oil based or water based? Look at the back fo the can and read what it says about clean up.
Arti Dyes are available at highlandhardware.com "Transtint" can be found at Rockier or Woodcraft. Welcome to the world of dyes!