Choosing Fragrance Oils
A few fragrance oil suppliers have a “sampler” option. You can choose a certain number of fragrances in small sizes at a very reasonable price. Soapmaker Lori Kimball of the Scent Shack created this option in response to the frustration of only being able to buy large sizes when she was shopping online for fragrance oils. Buying fragrance oils from a company founded by a soapmaker can be an assurance that the fragrances are appropriate for soapmaking.
There are many sources of fragrance oils. For the purpose of soapmaking, a fragrance must be “soap safe.” A soap-safe fragrance oil is formulated to react well with the various soapmaking processes. A fragrance that isn't soap safe for lye soapmaking can cause a soap batch to seize — become clumpy and hard as soon as it is added. It can also make soap separate, curdle, discolor, or streak. The scents may fade or mutate, making them unsuitable for soapmaking.
Since there are so many fragrances that are known to be safe for soap-making, there isn't really any reason to experiment with other kinds. For example, fragrances that are just for candles are not suitable to be used in soap. Some fragrances that are “multiuse” can be used for soap as well as candles and even toiletries.
There are some soapmaking fragrances that are safe for hot-process, soap-casting, or hand-milling applications only. Other fragrances cause visual problems with the finished soap. The most common cosmetic problem is discoloration. Responsible soapmaking suppliers will make this type of information clear in their catalog materials.
Don't try fragrances from “fragrance bars” in bath and body shops in lye soapmaking. You can try them in soap casting and hand milling, but try them in small batches first. It is really best to stick with fragrances that are intended for soapmaking.