Sidewalk Chalk, huge success. The 2 parts plaster of paris, 1 part water recipe was right on - the chalk was set and ready to go within 24 hrs and it writes just like the store-bought kind. Using little waxed paper cups as molds worked out very well - the cups came off the chalk just fine and cups are meant to be held just as much as writing utensils, so the ergonomics are good for the cup chalk.

Making the chalk itself was fun and easy, even more so when we got some of our Kraft Nite regulars involved. Everyone enjoyed the safe but messy mixing and chemical reaction process, especially the bit when you add food color to already mixed plaster and you get cool surface fractal patterns. I’ll be sticking around to do a repeat mini-workshop if anyone’s interested in playing around with making sidewalk chalk tonight too.

A couple of important tips that I learned in the sidewalk chalk creation process:

  • Don’t use unwaxed cardboard as a mold. It’s impossible to remove without the use of sharp objects to scrape off the cardboard that is now bonded to the chalk. If you really like the shape of cardboard TP and paper towel tubes, make sure to line them with waxed paper.
  • A whole lot of food coloring doesn’t go a long way. If you want to make a lot of vibrantly colored chalk, I recommend investing in quarts or gallons of coloring (which you can find online or in restaurant supply stores).
  • Mixing colors doesn’t always turn out how you’d expect. More often than not, red and blue made brown. Since green came with the food coloring set I got, that was no problem at all. I had more success with mixing cool colors, and warm colors together worked out once I added way more food coloring than I thought I’d need to. I think that with a metric ass-ton of food coloring, I could have create pretty purple chalk.
  • You’ll need to protect your furniture more than you need to protect yourself. Gloves were nice to have to keep my hands from getting crusty, but in the end I needed the cardboard I put down to protect the table more. The face mask was totally extraneous. If you’re working with rambunctious children, an apron is in order, but as long as no one starts a plaster fight, unprotected everyday or work clothes do just fine.