When I started trying to make my own bath products, I got a lot of instruction from the web. I read a few tutorials and a lot of recipes, then struck out on my own. Yesterday as I as preparing to make a batch of melts for a swap, it occurred to me that I ought to give some of that knowledge back and give a tutorial of my own. Due to my current emphasis on finances, I'm going to try to include prices here as well, so you can see how much these little suckers cost to make rather than buy.
How To Make Bath Melts
First, get your ingredients together. What you see here is an 8 oz jar of Nature's Flavors organic cocoa butter ($6.56, or $0.82/oz), a 16 oz bottle of Mountain Rose Herbs sweet almond oil ($6.50 or $0.41/oz), a five lb bucket of Majestic Mountain Sage coconut oil ($12.75 or $0.16/oz), 0.5 oz bottle of Aura Cacia sandalwood blended with jojoba essential oil ($10.69), and a 0.5 oz bottle of Wild Oats jasmine in jojoba essential oil, which was purchased on clearance for $6, but is generally more like $13.99 for 0.5 oz.
Next, get your hardware together. I used a thrifted Pyrex measuring cup, a postal scale I bought off Ebay (our kitchen scale is broken), a plastic chopstick for stirring, and a flexible rubber ice cube tray (also thrifted) for a mold. This particular mold holds 14 0.4 oz melts. Flexible rubbber molds like this one are my strong preference for making melts, as I have a hard time getting them out of harder molds without making a mess.
Once everything is together, start measuring out ingredients. Be sure to zero out the scale with the measuring up on it, then, to fill this size mold (5.6 oz total), add 3.5 oz of cocoa butter ($2.87 worth). You want your cocoa butter broken into smallish pieces if at all possible, and that's usually how it comes out of the container for me.
Next, measure in 1.5 oz of coconut oil ($0.24 worth).
Then, add about .6 oz of almond oil ($0.25 worth). Pour carefully--you can't take it back out if you add too much, and since almond oil is liquid at room temperature, adding too much will cause your melts not to harden.
Once your three oils are in, stir them up and then start your melting apparatus. I use a double-boiler method, as shown here, with a shallow pan of water heated slowly.
The coconut oil will melt almost immediately, the cocoa butter will take longer. As it melts, stir frequently.
As soon as the mixture is all melted, take it off the heat. The object is to heat it as little as possible while still getting everything fully melted. Do not be alarmed if it smells like chocolate and/or coconut--those are the butters natural scents and will be masked by the essential oils you add. If those scents bother you, you can buy deodorized cocoa butter, but it is much more expensive.
Once your melting is complete, you are ready to add your scents. In this amount of base liquid, I add about 60-80 drops of scent, depending on which scents I am using. The scents will smell stronger when added to the warm oil than they do in the finished product, so this is really a trial-and-error process. For the sake of this example, lets say I used .05 oz (about a tenth of the bottle) of sandalwood ($1.07 worth) and .05 oz of jasmine ($1.40 worth).
Once you have mixed in your scents, pour the mixture carefully into your molds. You want to fill them all the way up without going over the edges. It's a slow process.
Once the molds are full, they need to go somewhere to harden. Since it's still pretty warm in my house, I harden them in the fridge--they get harder faster that way, and it's a lot easier to deal with these as solids than as liquids.
After they harden for an hour or two, you should be able to pop them out of the mold easily and wrap or package them. My preferred wrapping methods are individually in foil and then together in a decorative fabric bag, or all together in a plastic bag and then that in a decorative bag, depending on how many melts we're talking about.
By my calculation, the total cost for this project (not including hardware, just ingredients) is $5.83, or $0.42 per .4 oz melt ($1.04 per oz). For the sake of comparison, my favorite bath melt from Lush, the Dreamtime, is $5.65/oz, and it contains artificial perfume as well as essential oils.
The upshot, of course, is that if you are a bath product junkie like me, it's greener and more frugal to make your own. If you don't want to make your own, though, come on over to Crushworthy--I am hoping to get new stock up this week, and I'll be happy to sell you some.