The commercial sodium silicate solution I buy is (by weight) 29% SiO2 and 8.8% Na 2 O, the rest being water. This is called Sodium Silicate 40 (the 40 refers to the viscosity), or SS40 in my notes. I modify this by adding sodium hydroxide. The purpose of adding NaOH is to further depolymerize the silicate, and thus make it more reactive. There is atleast one other form of liquid Sodium Silicate (I think called SS 50). SS50 may have a higher alkali to silica, but it is not available to me. The molar ratio is important, so pay attention to what you are buying. See the section on recipes.