Chalk is Calcium Carbonate, which is soluble in acids. However, carpenter chalk is chalk with an insoluble dye added for visibility. NOTE: The dyes used in Carpenter’s chalk are usually permanent and unaffected even by bleach! Label often even states that the stain is permanent!
- First, thoroughly vacuum - This is VERY important.
- Undyed chalk is readily soluble in mild acid.
- Heavily spray Brown Out® diluted 1 part Brown Out to 2 parts of water onto the chalk, work the solution in with a carpet rake or a brush and allow the acid to work on the chalk for at least 15 minutes.
- Agitate once again and extract thoroughly.
- If any stain from carpenter's chalk is left, blot with alcohol.
- If the stain is still not removed, use Stain Magic® and allow dwell time. Stain should disappear as it dries.