I'm still reading the same book I was last week, so let's make bubble bars instead, shall we?
Making Things Monday redux!
You're going to need baking soda, sodium lauryl sulfoacetate (NOT sodium laureth sulfate, that's different, and I will get to that in a minute), vegetable derived liquid glycerin, cream of tartar, and essential oils. You're also going to need a bowl, spoon, and measure devices.
In your bowl, mix up equal parts baking soda and sodium lauryl sulfoacetate. The baking soda is what makes it fizz, as well as being good for irritated skin and keeping things together in the bars. The sodium lauryl sulfoacetate is a foaming agent. However, unlike the evil sodium laureth sulfate, it is plant derived (from palm and coconut oil) rather than synthetic. It's also a "large molecule," rather than "small molecule" ingredient, which means it shouldn't irritate your skin (you can read a bit more about it here). Start with maybe one cup of each. Then add a couple of tablespoons of cream of tartar. The cream of tartar is there to help the bubbles keep their shape. Then add a couple of tablespoons of glycerin. The glycerin is to soften your skin and clean you, as well as assist in the bubbling. What you'll likely end up with it something that looks a bit like the bowl above--sticky, but not quite wet enough to stick together. Add the essential oils at this point. I find, for whatever reason, that I need to add a bit higher EO concentration to these bars than I do to melts or scrubs.
Once your ingredients are mixed, spritz them with water just until they're wet enough to stick together. You want to use as little water as possible. If you use enough glycerin and EOs, you may not need the water at all.
Then pack it into your molds. I use silicon shaped cupcake molds (or I use one of them--this is the only one I have and I really need some different ones). You want to pack it in as tightly as possible. Don't be afraid to use your fingers.
Once everything is packed in, it will look like this! Let them set up for about 24 hrs in a dry place.
Viola! Bubble bars! Crumble them up under fast-moving warm bath water and luxuriate!
Now, the math:
Baking soda is cheap. I buy big bags at Costco, which are, I believe, about $5 for 12 lbs. A cup is about .4 lbs. That makes the per cup cost about $0.17.
Sodium lauryl sulfoacetate costs $6.75/lb at Majestic Mountain Sage. A cup is about 1/4 of the container, or 4 oz, so I'd say $1.69 worth.
Cream of tarter is $9.69/lb from Frontier. The two-three tablespoons in this recipe add up to only about 1.5 oz, so that's $0.91 worth.
Majestic Mountain Sage sells liquid vegetable derived glycerin for $4/lb. Again, three tablespoons is only about 1.5 oz, so this recipe only calls for about $0.38 worth.
As always, the EOs are the expensive part. How much they cost varies widely based on how much you use and what types. A favorite bubble bar of mine from Lush is the Amandopondo Bubble Bar. It is scented with lemon, orange, and rose, so lets us that as a comparison. Orange EO, as we know from Monday, is cheap. This recipe would use maybe .2 oz, and it's $2.79 for 2 oz at best price, so that's $0.28 worth. Lemon is pretty cheap too--best price is found at Snowdrift Farms, and it's $4.49/oz. If this uses .2 oz (which is a generous estimate), that's $0.90 worth. Rose, however, is not cheap. The best price I've found for 5% rose in jojoba oil is $5.99 for .5 oz, at Frontier. If this recipe uses .2 oz, then, it's $2.40 worth.
Add that all up and this batch of bubble bars costs approximately $6.73 in a lemon-orange-rose combo. That's for 6 bars weighing slightly under 3 oz each--we'll say 16 oz total.
In comparison, the bar I linked to at Lush is $6.65 for one 3.5 oz bar. My per oz cost is $0.42, Lush's per oz cost is $1.90. To top that, the third ingredient in Lush's bar? Sodium laureth sulfate.
I win again!