One specific solution described is an aqueous solution of sodium silicate and a gelling agent such as an acid, an ammonium salt, a lower aldehyde, a polyvalent metal salt or an alkali metal aluminate.U.S. Pat. No. 3,897,827, issued Aug. 5, 1985 to Felber et al, describes a gel forming solution consisting of a dichromate activator and a lignosulfonate solution containing an alkali metal or alkaline