What is an ingredient that you can add to a runny liquid to make it harden?

I need an ingredient that you can add to a liquid thats runny and make it hard. It has to be edible, too.What is an ingredient that you can add to a runny liquid to make it harden?
Yes, Corn starch. Mixed in the right quantities, it will change before your eyes and in your hands from a solid to a liquid and back again. It can be great fun to play with. Start with about 2 cups of corn starch and add about 1/3 to 1/2 a cup of water and see what happens... add more water as needed. You can pour it on table and it will feel hard to the touch, but if you pick it up in your hands it will change to liquid and pour back onto the table, probably due to the heat of your hands. It is a great way to entertain children as well as adults. And it cleans up great and makes your skin feel soft. Seriously, try it, it is fun, but you will be hooked. I always keep a box of corn starch in my cupboard just for entertainment purposes. It is edible, but I wouldn't think it would taste very good.What is an ingredient that you can add to a runny liquid to make it harden?
flour?
cornstarch or flour
So much for concrete!
Gelatine
Cornstarch to Soups, Gelatine works with everything else.
Cornstarch, keep in mind though that it will thicken when it cools more than when its warm so try spooning it in one at a time. For very thick consistency try up to 4 tablespoons full per cup of water. For light thickness try 2 tablespoons...etc...
cornflour
gelatin and cornstarch do the job pretty well.