It's caused by a calcium buildup from the water..isn't it? The harder the water, the more calcium there is.

It's a hard water stain.

My bong has it
BobBong Reviewed by BobBong on . Cleaning the pHx ok... i wanna use the salt + alcohol method, cuz 420 is horrible now that its "all natural" I just dont like the white mineral deposits that the salt leaves on the inside of the glass... So my question is... Should i use : 1. Epsom Salt 2. Morton's Salt Rating: 5