Gak is similar in consistency to a thick slime. It's messy to make and play with but completely safe for children and good science activity, as well. Gak changes consistency as it's manipulated, becoming thicker when you handle it and more liquid when set down. The substance will stick to tables, floors or walls and peel right off. Gak can be made at home or in the classroom with liquid starch and other simple ingredients.
Pour 1 cup white school glue into a mixing bowl.
Add the liquid starch, 1/4 cup at a time. Stir each 1/4 cup in thoroughly before adding the next, until you've added the entire cup.
Drizzle in extra liquid starch if the gak feels sticky instead of rubbery and smooth. Stir the extra starch in with your wooden spoon.
Color your gak with a few drops of food coloring or Kool-Aid powder. Keep in mind that adding either can cause color transfer to your hands and other surfaces.
Add fragrance to your gak with a couple drops of your favorite essential oil.
Press gak into a newspaper to transfer the ink to your gak.
Store gak in a plastic zip bag, kept in a cool place, for up to a week.