Ah well. I use that combination more or less, except mine is Plantarem APB which also includes ALeS and doesn’t use DEA but instead high-purity DEAL. I do work with TTO and I have been experimenting with it in shampoo between 0.05% and 1%.
First let me say that the following applies to the blend you’re using in that it’s an anionic shampoo.
I guess you’re salt thickening since you don’t mention CAPB. With that blend, let me say that I think you’ll find that using CAPB as a thickener will give you a much superior shampoo, you won’t need more than 5% probably, and CAPB is very very cheap and easy to get.
You don’t mention if you are trying for a clear or are going with pearl. Anyway, in my experience getting a clear with anything more than 0.07% of TTO is not really possible. Even at 0.1% you get translucent.
1. Be careful with TTO concentration in shampoo type products incl body wash. I had reports of dermatitis type reaction (scaly patches) on my tests at 1% TTO. It is pretty strong stuff. Have you studied the data on the Min E Dose to kill a population in 24h? It is tiny, a lot less than 1%.
2. TTO is expensive and body washes are an extremely price-competitive market. Plug 1% in to your retail price formula and see the result.
Well if I haven’t put you off yet, I use it in our frequent use 2-in-1 shampoo but only at a level of 0.07% and even at that level it should have an effect on scalp health, in that it’s a potent antifungal as well as antibacterial. I would suggest using 0.1% and going for a pearled formula.
Regarding the viscosity problem, yes, it is a really difficult one to work with, but you will find that at 0.1% it is quite manageable, just adjust the test batch with CAPB until you get the right viscosity. I suggest waiting 24h then readjusting as necessary as it seems to drift a little.
The alternative is to go sulphate free but then your price is out the window straight away.