Things You'll Need
Instructions
Mix 10 parts water with 1 part oxalic acid in a microwavable bowl.
Place the bowl in a microwave and heat it for 30 seconds.
Dip a cloth into the mixture. Wring out the excess liquid and rub the cloth on the water stain.
Let the mixture sit on the stain for 1 minute.
Run a soft, brass brush under cold water, and rub it over the water stain.
Dry the guitar with a dry cloth.