Remove alkali spots at once; they may destroy not only the color but the
material as well. First sponge or rinse the spot thoroughly with cold
water. This generally is sufficient for mild alkalies such as washing
soda and weak ammonia water. But to be on the safe side and to help
restore color, apply an acid—this stops the action of the alkali. Then
rinse or sponge the spot thoroughly with water. Use any of the following
mild acids:
Lemon juice.—Squeeze the juice on the stain, and allow it to remain
until the juice loses its bright yellow color. Sponge or rinse well with
water.
Vinegar.—Sponge with vinegar; then rinse in cold water.
Acetic acid.—Apply a few drops of a 10-percent solution of acetic acid
with a medicine dropper or a glass rod and remove the excess by rinsing
or sponging with water.