Can I use the Pure-Castile Magic Soap with salt water?Updated a day ago

While our Pure-Castile Magic Soap can be used in or diluted with salt water, because of the high mineral content, we typically don’t recommend using it with salt water.

Salt water is considered hard water, as it contains dissolved minerals such as calcium and magnesium. All true soaps, such as our liquid soap, will react with these minerals to form insoluble stearates, which are visible as a whitish precipitate. This can cause your dilutions to turn murky or cause separation, though it doesn't affect the soap's ability to clean. However, this effect can interfere with foaming capabilities and may leave soap scum on surfaces. 

This whitish residue mostly builds up on surfaces where water dries, like sinks and showers, and usually isn’t a problem on floors, counters, or other hard surfaces where you mop or wipe up the water. If you do see residue, you can dissolve it easily with vinegar. Mix 1 cup (240 mL) of vinegar with a quart (1 L) of water, spray it on the area, and let it sit for about 5 minutes. Then rinse with very hot water. If the residue is really thick, you might need to repeat the process or use a stronger vinegar mix.

If you want to learn more, check out Lisa Bronner’s blog posts, The Chemistry of Water and Using Soap to Test for Hard Water.