mixture foaming is then initiated by mixing with the other component of the 2 component system for example with addition of water the carboxylic acids must have a ph sufficient under the conditions of mixing to release carbon dioxide which acts as a foaming agent from the carbonate as inorganic carbonates those carbonates are preferred which are easily decomposed while giving off carbon dioxide especially the carbonates of multivalent compounds carboxylic acids which form a component of the foaming agents include polyacrylic acids and their derivatives such as polymethacrylic acid copolymers of acrylic acid and or methacrylic acid with itaconic acid and or maleic or fumaric acid and or acrolein preferred are carboxylic acids which are polymerizable or copolymerizable themselves and also carboxymethyl cellulose acid form alkyl and acryl polycarboxylic acids etc as inorganic carbonates especially the carbonates of multivalent metals such as calcium carbonate chalk calcite magnesium carbonate magnesium hydroxy carbonate calcium magnesium carbonate dolomite zinc carbonate zinc hydroxy carbonate etc have proven their value the use of carbonates of multivalent metals has the advantage that after the carbonate is decomposed by the organic carboxylic acid with release of carbon dioxide the remaining metal ions form carboxylate groups with the carboxylic acid groups of the organic carboxylic acids the compounds thus formed lead to cross linking and thereby to an increase in the.