Place the damar crystals in the center of the cotton cloth and wrap the ends together and tie with string to make a bag. Follow the instructions on the package for the right amount of crystals.
Pour the turpentine into the pint container. Place the bag of damar crystals inside of the turpentine leaving one end of the string outside the jar. Make sure the damar crystals are thoroughly wet.
Close the lid of the jar leaving the string outside. If your jar won't close you can leave the string on top the bag. The crystals need to be immersed in the turpentine for at least two days. Stir the contents twice a day.
When the crystals have dissolved you can remove the bag. You can transfer the varnish to another container and discard any debris that has settled to the bottom of the container. The solution should be a golden yellow color.
Your varnish is now ready to be used to seal your tempera painting. Damar varnish will give your painting the look of an oil painting