PEBEO Studio Crackling Modeling Paste Set is to increase the adherence of the modeling and facilitate the appearance of cracks, it is strongly recommended to prepare the surface with the Step 1 Under Coat medium. The Crackling Effect Modeling Paste (step 2), of a paste-like consistency, can be applied with a painting knife. It can be used pure or mixed with Studio Acrylics colours (75% modeling/25% with acrylic colour).