I found this awesome article online on how to make chalk and thought it would be perfect for outside sigils. I haven’t gotten a chance to experiment with it yet but I think rather than using food dyes I’ll try to create a natural dye from herbs. Also, if the process allows, I’ll try to grind lavender super fine and add it to the chalk. (But it may not work!) So when I get a chance to mess with this, I’ll post the results!
Here is the article:
Let me know if this article link works!!!
Update, now posting with a picture! (The picture comes from: