- 1). Wash two 8-ounce jars and their lids in hot, soapy water, then invert them on the counter and leave them to dry.
- 2). Place 8 to 10 sticks of white, calcium-based chalk in a plastic storage bag; set the bag on a flat surface, and then use a rolling pin to crush the chalk.
- 3). Scoop 2 tablespoons. of powdered chalk into an ovenproof glass bowl or heavy-duty jar. Add 1/2 cup distilled white vinegar and 1/4 tsp salt. Stir the mixture for approximately five minutes.
- 4). Strain the solution to filter out any remaining chalk pieces, and then return the mixture to the container. Set the container in the oven. Bake at 200 degrees for 30 minutes, or until half of the solution has evaporated.
- 5). Divide the remaining mixture evenly between the two jars. Add 1/3 cup rubbing alcohol to each jar. Stir briefly, then stand back and observe. As the alcohol reacts with the calcium from the chalk and the acetic acid from the vinegar, the mixture will take on a distinct, gel-like consistency.
- 6). Pour off any remaining liquid. Seal the jars and use as needed.