Are you making liquid soap (LS) that needs to be neutralized or are you making LS that is slightly superfatted? If the former, I recommend formulating your recipes so you have up to a 3% superfat.
Here are two tutorials on the superfatted LS method:
Irish Lass:
http://www.soapmakingforum.com/showthread.php?p=428988 see posts 8 and 9
Susie:
http://www.soapmakingforum.com/showthread.php?t=49852
A properly formulated recipe with a slight superfat will result in a liquid soap that is the right pH for the blend of fats you've used. If you've done everything right, the pH will be fine for that particular soap, and it really doesn't matter what that pH is. Most likely it will be somewhere between 9 and 11 for most balanced blends of fats.
If you've done something wrong, testing the pH isn't really much help, despite the huge emphasis on pH testing in some LS making books and Facebook groups. FIrst of all, a pH test is often highly inaccurate since its seldom done properly. It also does not -- repeat, does not -- give accurate feedback on whether there is excess alkalinity (too much lye) in the soap or not. Far too much liquid soap has been ruined by soapers' desperate attempts to force their soap to have a pH that is not realistic.
For that reason, most of us liquid soapers here on SMF generally don't pH test -- we zap test instead. The zap test gives a better sense of the excess alkalinity. If you get a zap, you can add a small amount of fat into the soap, allow it time to saponify, and zap test again. Repeat until zap free. If you get no zap but see your soap is separating when diluted, you can add a small amount of lye solution to the diluted soap and allow it time to saponify. A successful result in this case would be when the diluted soap is still zap free, but no longer separates.
About the zap test, here's how I do it -- If you have any shred of doubt about your soap being zap free, do not, DO NOT touch your tongue to the soap. Rub your fingertip lightly on the soap and lightly touch said fingertip to tongue. If you get a zap, rinse your mouth immediately with cool water and spit, don't swallow. If you do not get a zap, feel free to lick on your soap to your heart's content.
