I do the it the same way Brenda described. I went through several fragrances that didn't throw at all and realized that I was wasting a lot of time, wax, etc. I do reuse my testing jars over and over. I do not offer refills to customers, they only get new jars. The primary reason for this is because I just know they'd be bringing in dirty jars, wax left in them, etc and it would really be too much work for me to clean them. Call me lazy, I guess However, I do agree that exploding jars would not be good. LOL!