A microwave? To make wheat starch paste, mix the wheat starch powder with distilled water in a microwave-safe container. Stir until blended, and microwave for about 20 seconds. Remove the mixture, stir it and then microwave for another 20 seconds. Repeat the stirring and microwaving until your paste is stiff and translucent. Nothing else may be cooked in the microwave, especially not food. Contaminants may limit the efficacy of the paste or invite unwanted interlopers, like insects and mold, into your books or papers.