I've not heard of putting vinegar into soap. Sounds very intriguing!! I have a couple of questions.
- Does the acid counteract the base?
- Would you need to add extra lye to counteract the acid?
- What is the purpose of adding vinegar?
Yes, if you add vinegar before the soap is fully cooked, you have to adjust (increase) the NaOH since the vinegar and NaOH will react to form sodium acetate. Thus, it will not reduce the soap’s pH as so many people think it will. If you add it post-cook, no lye adjustment is needed, and it still won’t adjust pH by much. Soap by definition is high pH.
Any vinegar containing alcohol, like wine vinegar, will cause the soap to seize if it is added before the cook has completed. Darker vinegars (balsamic, ACV) will darken your soap, and those with additives (flavored vinegars, many wine vinegars) will have other effects. White distilled vinegar is easiest to use, but some folks avoid it because it is usually corn-based, at least in the US.
That being said, I love using distilled white vinegar as a water replacer and did so regularly before I began MB’ing my lye solution. I did adjust the lye accordingly. The sodium acetate that is formed helps the soap firm up faster and unmold more cleanly. And the lather has an extra je ne sais quoi
- a softness, maybe? I encourage you to give it a try!
You do have to add the NaOH very slowly to the vinegar. One time I carelessly dumped it all in, and had a crazy lye solution volcano everywhere!