Enhancing the grain on maple is something gunstockers love to do. The main, not so secret 'secret' is nitric acid. Using a dilute solution, you can wipe on and watch the effect. Want more, just do again. It can take time. Most use a very dilute solution to bring out the grain exactly to the point they want. Then it is rinsed with a neutralizing solution to stop the darkening. Sanded and finished. FWIW, on gunstocks, a high quality boiled linseed oil is preferred.
Sometimes, the acid solution will have fine iron filings dissolved in it. That or fine steel wool works. To get really disgusting, some add tobbaco for more color. It works.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire