Fill two parts of a medium size glass bowl with hot water (almost to a boil). You can also warm the water to the desired temperature using a microwave.
Add two parts of ammonia or glass cleaner to the bowl containing hot water. Stir a bit to mix ammonia and water.
Gently place the ring in this concoction and let it stay for a couple of minutes.
Remove the ring from the solution, making sure you grab it by the metal. Rub it gently with a soft bristled toothbrush, to wipe away the grime on the inner side of the ring and birthstones.
Once all the grime is gone, and the ring looks brand new, rinse it thoroughly with clean water.
Set the ring on a paper towel or a dry soft cloth for at least five minutes to let it dry.