This time we made pumpkin-spice cake-in-a-jar, which is this really hilarious phenomenon in which you can bake a little cake right in a little mason jar, then pop the lid on right when it comes out of the oven and it will seal, and then it's perfectly preserved for at least 6 months.... a fun way to send a little baked goodie to someone far away. We also made fizzy bath bombs, which is REALLY exciting and they do fizz quite excitingly and dramatically as we observed when we tried them out in the water table. The only trouble is it's a bit hard to find the balance between making the mixture wet enough so that it will hold the shape of the mold, but not quite wet enough to start reacting (if it's too wet the citric acid in the bath bomb will start fizzing, not what you want). I used this recipe but I feel there is probably a better one out there. Last year I did this project with my gift making class and it worked out perfectly... need to search out the recipe I used. Alternatively you don't need to shape it into a 'bomb' at all.... just put the dry mixture in a jar, maybe with a little essential oil mixed in for delicious smells.... add a few spoonfuls at bathtime for fizzy delight!
By the way, citric acid can be found at Fiesta in the kosher section, also known as Sour Salt. Someone else said they saw it at Central Market in the bulk section. You can also easily order it online.