We tested each essential oil starting at a 6% fragrance load, and raised or lowered the percentage depending on the strength of the hot throw. This testing process allowed us to customize our recommendations in hopes of minimizing the amount of testing our customers will need to perform. Essential oils were tested up to a 10% fragrance load. We recommend keeping the total essential oil load at 10% or below and following each essential oil’s usage instructions listed on the product page. However, we encourage you to test and find the essential oil load you prefer for your candles.