Fine gravel (even chunkier will work!) was mixed with modeling paste on the left. In the center, sawdust. And at right, clean eggshells that have been crushed.
Can you think of other materials to mix with molding or modeling paste? Chopped up threads, for example, or sand.
Thanks to the publisher for allowing us to show you this photo ffom the book, just one of many, many full-color pictures!