I just discovered this post on Savvy Housekeeping.
"How To Turn A Bar of Soap Into Liquid Hand Soap
1 c soap flakes
10 c water
1 Tbs glycerin
A large pot
Measuring cup and spoons
A spatula for stirring
A soap container with a hand pump
A container to hold excess soap
First, grate the soap. Get out your cheese grater, grab the soap, and get grating. I found this to be surprisingly easy, although the soap particles tend to float in the air as you grate. You can wear a mask to avoid breathing it in. When you’re done, the soap flakes look like grated Parmesan:
One bar of soap yielded a little over 1.5 cups of flakes. The recipe only uses one cup of soap flakes, so I put the remaining soap in a jar for later use.
In a large pot, combine 1 cup soap flakes, 10 cups water, and 1 Tbs glycerin. Turn on medium-low heat and stir until the soap dissolves. This happens fast, about a minute or two.
Let the soap cool completely, then pour into the containers using the funnel. That’s all there is to it!"
From Sabrina: I am going to try this possibly tommorrow. Wednesdays are the farmer's market so it will depend on whether I get everything ready in a reasonable amount of time or not. I have some glycerin soap base that I haven't done anything with so I'll melt it down and try making it liquid which we use a lot more than bar soap.
If you have the urge to be adventurous and try this check out the comments on the Savvy Housekeeping blog before you try just to have a heads up of some issues others have experienced. Remember, every bar of soap will have different ingredients. The type you choose will affect the amount of water and glycerin you should use. If your batch doesn't come out perfect the first time, keep trying. If it is too thick, add a cup of water. If it is too runny, boil off a little bit of the water. I recommend letting it boil for 10 minutes then sit overnight to congeal. If that's not enough, boil for 10 more minutes.