Wax is my favorite sealer for polymer clay other than resin. Are concrete sealer fumes toxic? If the estimated time seems a bit long, it’s because many items are shipped in bulk at the end of the sale (on Dec. 16), which is what affords you the discount. Chalk is not like most other paints and the first time I used it was to paint over my kitchen table, chairs, and cabinetry. Answer: According to the ASTM standard for conducting a calcium-chloride test (ASTM F 1869), a reading above 4 pounds—the amount of moisture flow in pounds per 1,000 square feet over a 24-hour period—is considered a no-go for sealing. Of the many painting jobs, I’ve performed over my career, working with chalk was certainly one of the most interesting. I’ve found that waxes tend to have a really strong smell compared to most other sealers and it can take some getting used to.