I do not know, how it works in the U.S.A., but here in Germany I can buy menthol-cristalls and 96% ethanol at the pharmacy. I put 10 g of menthol cristals in a brownglass bottle and mix it with 10ml ethanol (96%). Then I shake it until the cristals dissolved in the alcohol. If it is hard for you to buy 96% ethanol, you can also use 100% PG without nicotine. This needs more time to dissolve the cristals, but it works as well. A few seconds in the microwave may help, too. No you have a menthol flavouring. Dont use it to vape it isolatet in your PV!!! This flavouring will be used as an admixtureto your eJuice. It depends on you how strong you need the menthol power. Normally people use 2-5% menthol in their e-juice. So beginn with 0,1 ml inside a 10 ml e-juice-bottle and add until you have the intensity you like. But please, always be carefull because it could harm you if it´s overdosed. And be aware of protect yourself every time you handle with menthol. It is very aggressive in the pure form, and the flavouring also can cause probs if unsed wrong. Avoid eye- and skincontact and dont bring it onto any kind of muctous membrans. But if you really like menthol, this is the purest way of enjoying it!