The hardness of the clay obtained from different sources is different, so it is necessary to add water to make it soft. Usually, you need to add about 12% by weight of water to the clay. Of course, you can also add ethanol. The evaporation of ethanol helps the model to dry. It can be compared with the softness of toothpaste by contrast method, such as crest toothpaste, clay. It needs to be harder than toothpaste.