Sorry, I missed this question earlier. You can use the SoapmakingFriend calculator to automatically calculate the extra lye for your vinegar. The other option is to do the calculations by hand. Here is a good website that explains this. and a copy of the explanation from that site:Could you show me how to do the calculation for vinegar only? I don't want to MB lye solution.
How much lye does vinegar neutralize?
Commercial vinegar sold for cooking and household use is 5% acetic acid. About 1 fluid ounce (2 tablespoons, 1 ounce by weight, or 28 grams) of this commercial vinegar contains 1.5 g acetic acid.
1 oz by weight (28 g) of commercial 5% vinegar neutralizes about 1 g NaOH.
How to calculate the extra lye needed to neutralize the vinegar?
When using vinegar in your recipe, add the appropriate extra weight of lye needed to react with the acid. If you do not add any extra lye, the acid will increase the superfat in your soap.
Decide how much vinegar to use. If you aren't sure, I suggest using commercial vinegar for half of the water in your recipe. For example, if a recipe calls for a total of 200 grams of water, use 100 grams of vinegar and 100 grams of water.
NaOH for vinegar, grams = Vinegar, grams X 1 / 28 = 0.0357 X Vinegar, grams
Total NaOH, grams = NaOH for vinegar, grams + NaOH for saponification, grams