Maple hardwood floors are tough to stain. The tight cellular structure of the wood makes it difficult to get a stain to penetrate properly. Maple is also known for having an inconsistent grain pattern, often leading to blotchy stain finishes. The Maple Flooring Manufacturers Association actually discourages the practice. This doesn't mean it can't be done. It just takes some time and preparation to get the process down.
Step 1 - Choose a Stain
The type of maple you are working with will have a lot to do with what type of stain works best. Hard maple will fair better with lighter stains. Soft maple will take lighter stain colors, but shades of gray can still come through in certain lighting. If you are working with hard maple, you will want to choose a stain that is slightly heavier. This will allow the stain to settle more evenly. Another option is to just use a clear coat finish on the natural floors and forgo the staining process.
It's also best to avoid water-based stains. While these will clean up much easier than alcohol or lacquer stains, they can cause the wood to warp and will raise the grain. Alcohol or lacquer-based stain won't contain damaging amounts of water, and they will dry much more quickly than a water-based stain.
Step 2 - Sanding
Hand sanding maple flooring is a big job, but it is the best method for preparing the floor to accept the stain. Sand with a 120-grit paper and follow it up with a 150-grit paper to provide a swirl-free surface. While you sand, keep an eye out for glue spots that may be left from the installation process. The glue will act as a barrier, and the stain won't be able to penetrate through the glue. You can sand away glue spots as you work to avoid uneven staining areas.
Step 3 - Ventilation
Anytime you work with stain, ventilation is necessary. With maple flooring, however, too much ventilation won't allow for the stain to dry evenly, leaving an uneven finish. Without this, you may be forced to work with 2 coats of stain for an even finish. The best way to combat this is to ventilate as normal and wear a mask.
Step 4 - Staining Techniques
When working with maple flooring, it's important to pay attention to the direction of the grain. Apply the stain with the grain for maximum penetration. It's also important to make sure the rag you use to apply the stain has an even amount of stain with each pass. You will have to work with maple more than other types of wood to ensure the stain will soak into the wood evenly. Make sure you rub the stain in well and evenly.