ethylenically unsaturated carboxylic acid such as acrylic or methacrylic acid such compositions contain more than one ester linkage and are ethylenically unsaturated and hence can be characterized as unsaturated polyester resins the copolymerizable monomer whih is the carrier for the unsaturated polyester resin is usually an ethylenically unsaturated compound such as styrene vinyl toluene divinyl benzene acrylic esters methacrylic esters acrylic acid methacrylic acid and the like customarily the copolymerizable monomer comprises from about 15 to 35 percent by weight of the unsaturated polyester resin syrup with the unsaturated polyester ingredient comprising the remaining 85 to 65 by weight of the syrup the syrup may also contain small quantities of polymerization inhibitors such as hydroquinone the composition may also contain thixotropic additives such as silica aerogel suitable unsaturated polyester resin syrups are available from a variety of resin manufacturers in the united states the present composition also employs an inorganic carbonate or bicarbonate preferably an alkaline earth carbonate or bicarbonate such as calcium carbonate calcium bicarbonate magnesium carbonate or magnesium bicarbonate other inorganic carbonates or bicarbonates which might be employed include carbonates and bicarbonates of lead nickel zinc aluminum potassium sodium and naturally occurring carbonates such as dolomite limestone marble and the like these materials are relatively inexpensive and readily available in the course of the present reaction the inorganic carbonate or bicarbonate is converted to carbon dioxide gas upon contact with the acidic aluminum chlorhydroxide which is contained in the b component for the purposes of dispersion in component.