Menthol crystals are used at a rate of 1.5% to 2%. Crush the menthol crystals and dissolve them in your essential oil blend to add to the cream during the cool down phase. Add to your oil phase in a salve. To use Menthol crystals Using in a salve: Melt all ingredients together except for the menthol and essential oils. Remove from heat, stir in menthol crystals, re-heat until crystals are melted if needed. Remove from heat and let cool before stirring in the essential oils or they will evaporate, pour into containers. If you don't have experience in using menthol crystals, they are quite powerful, so do wear a mask when using them and caution, you don't want to have your head right over the bowl when mixing this item.