I’ve ordered some L-Arginine HCl for testing.
As a first test, I added 4 grams of it to 46 grams of store-bought SAPDMA-based conditioner. So about 8% L-Arginine HCl or 6.6% L-Arginine. The change in viscosity was immediate, it got so thick I could barely stir it. I applied it to my hair as I normally do, about 15 grams spread using a wet detangling brush on wet hair, and leaving it in.
Compared to the same conditioner without the Arginine, I feel it works a little worse as a wet detangler because of how thick it is. However, it does seem to work otherwise as intended – my curls appear stronger and more defined, without the gloss that some other products give to my hair. If I add more of the stuff to my hair, it works like hair gel, but less glossy/oily.
I will continue to test it for a few more washes, also see if I can apply it just dissolved in water as a hair mask. I want to understand better what it does before I start formulating with it.