My kids love cool (/ gross!) sensory activities, and so I'm always on the lookout for fun things to explore together. We've explored oobleck here before, and when I saw this project for homemade slime on this awesome site, I knew we had to check it out during the Halloween season.
Borax (sodium tetraborate) is a naturally-occurring mineral salt commonly used as a laundry booster or cleaner. As with any other cleaning product, it should be kept away from children not under direct supervision of an adult. Do not allow children to ingest Borax. If consumed, contact a poison control center immediately. Wash hands after play, as prolonged skin exposure may cause irritation.
Note: This works just fine without food coloring--you just get white slime and you don't have to worry about staining clothes or fingers. Also, borax powder is available at most large grocery stores.
Then, add one tablespoon of the Borax mixture into the glue mixture. Stir well and observe how the watery glue begins to solidify just a little and turn into slime. Depending on how much glue you put into your cup, you may need to add a bit more Borax solution. Go slowly on adding the Borax stuff--your glue mixture will go from slime to solid pretty quickly (as ours began to.)
Whoa, so cool!! Let your slime sit for a minute or so, then you can pull it out and play with it! Our fingers did get a little stained from the food coloring, so I would probably skip the food coloring next time. Also, you can put the slime in a ziplock bag for storage or as a mess-free way to play.