I receive many questions about adding fragrance oil (or essential oil) to soap dough. I have covered this topic in my books both The Magic of Soap Dough and An Enchanted Book of Peculiar Ideas and Soap Potions.
My first suggestion while learning to make soap dough is don't! Avoid scented soap dough when you are learning what to expect from soap dough. A great quality of soap dough is smooth, pliable and soft, but firm. After all, we don't want lumps in our dough. Fragrance oils can cause the best cold process soap recipes to go sideways. When learning something that takes a bit of nuance, keep it as simple as possible. That is, until you begin to see more deeply into the this artistic craft - soap dough.
It takes a minute to learn how to make a great quality soap dough. Anyone can do anything. Anyone can make soap dough. Making good quality soap dough takes time.
How To Tell Quality?
Look at those who make extraordinary soap dough embellishments and embeds. (See: Soap Interviews.) Those who make exceptional embellishments or embeds are the standards. Those enchanting soaps that grab your attention; are neat handed and free of soap crumbs; that look so smooth it bodes a question - Are those soaps?
How to Choose
When I began studying photography, many years ago, the first thing I did was search all those I followed on Flicker. There was a section on each posted photo of "equipment used". I made a list of the images I most loved and took notes on what equipment they used. I had to make a choice, Nikon or Canon. After all, once committed to the body or a camera there are lenes to choose.
I chose Canon. Simply because the images I was most attracted to were created by Canon equipment. Do not misunderstand. I didn't, for one minute, think I could create stunning images just because I bought equipment. I wanted to emulate those I admired. I had to start somewhere. Indecision is a barrier to progress.
With soap dough, do what others (even me, who has written a few words about soap dough) do, for awhile. If you desperately need to scent your dough at least practice with soap dough a bit before you make fragranced soap dough. I've been making it for years and I find it a monster to manage.
If You Must
If you must, if you insist, on fragrancing your soap dough, at the very least choose a fragrance that is tried and true. Read the Soap Dough books. Find ways to avoid the issue.
Why Is Fragrance Oil Tricky?
I go over this in my books, AND it needs repeating... Fragrance oils are complex. They bring, not only OIL to the table, but chemicals that affect the quality of the soap dough that goes largely unnoticed. If the traditional fragranced cold process soap bar behaved it's a relief. If there wasn't acceleration, over-heating, or ricing... No one pays much attention to the soap texture. Not just the texture of the surface of the bar, but what the soap feels like inside.
Not the case with soap dough. We touch it, dig into it, and our fingers tell us information about the quality of the soap our eyes cannot from bar soap.
This topic is so important I dedicated a chapter to this subject, (Chapter 6: Page 35). I share how to avoid issues and how to add fragrance oil to soap dough.
By the way, I never scent my soap dough. I find it unnecessary. The soap embellishment is generally so small the scent of a bar of soap trumps the embellishment scent. I eliminate the as many issues as possible and share those insights with you in all my books.
I ran into many issues while untangling the soap dough issue. I share the straighter path, how to avoid problems, so you can get on the with the business of manifesting your creativity. No one wants to get hung up on a problem someone else has figured out while dreaming of a new and fantastical soap. Researching issues, finding the work-around, takes time. A lot of time. I've condensed time in the Soap Dough books, shorten the path for you.
Go forth, little soap witch, and create! Manifest your ideas into a product of great care. One bar of enchanted soap might help change things... If nothing else, the very bottom line, you will bring joy to someone else with your magical soaps.