Do not use a glass measuring cup on the stove top as it may explode.
Some waters take less time.
If it is a darker color, it means you have too many impurities. Try another type of water as the water is almost always the variable. If gray or black flakes appear, filter before using. The red light should remain off when making the colloidal silver. If the red light comes on it means there are too many impurities or minerals in the water.