Goop is made by mixing cornstarch and water. I didn't really measure when making it, so I can't give you an exact recipe, but I would recommend just starting out with a healthy amount of cornstarch and then adding water until you get the right consistency. The consistency of goop should feel solid when you squish it in your hands, but as soon as you let go it should turn into a liquid and melt right off your fingers. If you want to, you can add coloring to your goop, which we did eventually, but we started out with white goop.
Izzy loves messy play but is always very cautious at first and usually starts out by poking one or two fingers into the mixture. After he has thoroughly poked it, he usually dives right in. Once that happened I feared for the safety of my camera and had to put it away to protect it from the goopiness. This unfortunately resulted in only one picture of Izzy and the goop.
Goop is perfect for babies because it is completely edible although it probably doesn't taste very good. In fact, Izzy took a bite and then decided he didn't want anymore after that. This is a miracle because the kid eats everything! So I know it must not be particularly appetizing.
The messiest part of this activity was the fact that Izzy tried to be a goop artist and paint my floor. I couldn't get mad though because I could tell he was being so deliberate with his artistic skills that it was just adorable. However, my floor ended up looking like this...
Cost: $1 for cornstarch
Skills learned: Fine motor, colors
Age: 9m+
Rating (out of 4 stars): 3