. "e method works particularly well with foaming agents of the general formula: RO(R'O)n RSO3 Mwhere R is an alkyl radical, branched or linear, or an alkylaryl radical such as an alkylbenzene, alkyltoluene or alkylxylene group, having from about 8 to about 24 carbon atoms, R' is ethyl, propyl or a mixture of ethyl and propyl, n has an average value of about 1 to about 20, R is ethyl, propyl, hydrox" . . .