I just built a maple cabinet, and before applying any sort of finish I read a lot about it. The overwhelming agreement seems to be that maple is very difficult to stain evenly. Different areas of the wood absorb the stain differently, resulting in a "splotchy" finish. I've tried pre-stain sealers before on pine and didn't see much of an improvement, and from what I've read the same is generally true for maple.
Apparently, most professionally finished maple pieces are not stained at all, but rather coated with a dye-containing finish. I've read lots of posts by the professionals on the woodweb.com forums, where they talk about achieving excellent finishes on maple through various many-step processes involving countless special chemicals and custom-mixed dyes. In a typical scenario the wood is pretreated, then dyed to a uniform under-color, then sealed, then stained, then sealed again, then finished with a non-grain-raising coating into which custom dyes are mixed, then finally finished with a lacquer or other clear coat.
As a recreational woodworker, this whole process sounds intimidating, time-consuming, and expensive. I decided to try my luck with a simplified version, and I have to say, the results are great.
Here's what I did: First, I applied one good coat of oil-based polyurethane over the bare wood. That sealed it up nicely so that no subsequent coloration would soak into the wood but would instead remain on the surface. I used the cheap Minwax fast-drying poly in the spray can from Home Dep*t or L*wes. After allowing that to dry, I then sprayed on a couple coats of the Minwax Polyshades. That's the stain-and-polyurethane-in-one product. I've heard aweful things about it in the past and as a self-respecting woodworker I never would have used it until I needed to try this experiment. I sprayed it on using a cheap $29 air-brush (also from Home Dep*t) connected to my compressor. I turned the feed down really low, and I was able to spray on the color slowly and VERY evenly. I could even match out some of the color variation in the wood. I just had to be patient and not spray on too much at once or else it would have dripped. Once I had the depth of color that I wanted (more coats make it darker), I finished it off with one more coat of plain polyurethane. It looks beautiful.
Besides being very uniform on maple, another advantage is that glue joints or other places where glue may have soaked into the grain of the wood (this is expecially problematic on open-grained woods like oak or ash) don't show up as light spots in the final product. The color goes on uniformly on top of them just the same.
One disadvantage of this technique over the more complicated stuff the pros do is that if the finish gets scratched, the light wood will show through. Nevertheless, unless Minwax goes out of business, it'll be pretty trivial to fix. Another disadvantage is that there aren't many colors to choose from in the Polyshades line. I wanted a color that was warmer than the stark whiteness of the plain maple (and which would contrast with the bare butcher-block top I made for the cabinet) but not so dark as to darken up the kitchen (I plan on eventually redoing all the cabinets). My wife picked out Honey Maple and Pecan as two possibilities. They were two yellow and too red respectively, so I mixed them 50-50, and the color came out exactly what we wanted.
This might not be the absolute best way to color maple, but it worked pretty darn well and you don't have to be a professional finisher or buy any expensive specialty chemicals to do it.
Josh