Cael loves to play with this "GAK" stuff. It is a slime --- even better than play dough in his mind. We have made it for several years, and it is always a hit. It's gooey and slimy and keeps well in a ziploc bag. The recipe is:
1 cup Elmer's Glue
3/4 cup water
Mix above together in a bowl.
Separately, mix together
1/4 c. hot water
1 tsp. Borax
Slowly add the two together. The mixture will immediately coagulate together.
Knead, then drain off excess water.
This is perfect for upcoming haunted houses. You can also tint it another color with food coloring if desired.