The first recipe called for 0.25c grated castile soap, packed, which made for a difficult time dissolving in hot water. I guesstimated about one cup unpacked as a rough equivalent.
To make it slightly less solid, I increased the water from 1.25c to 1.5c, melted, and added the other ingredients in turn.
This experimental batch contained the following ingredients:
- 1.5c water
- 1c grated castile bar soap
- 1 tbsp washing soda
- 1 tbsp glycerine
- Boil water, adding and stirring grated soap until dissolved.
- Add washing soda and stir in.
- Add glycerine and stir in.
- Pour into a heat-resistant container (eg, mason jar) and let cool.
After an hour, the soap had an excellent viscosity exactly as I had hoped for. Unfortunately, the next morning, it had a Gak-like consistency.
And since then, it has become more solid -- still soft enough to scoop out with a dobie, but certainly not free-flowing. More water next time?
This version seems to do a reasonable job of cutting grease, so I think it is better than the previous two.