Saturday, January 16, 2010

Melt & Pour (MP) soap from rebatch material.

*** 01/16/2010 Updated to include transparent soap at the end of this post ***

I have been playing with making MP soap from BDG. One of the methods I've been using to experiment with is by using bar soap scraps. I did a re-batch of both of the bars of soap from the last blog. One of them is a BDG bar and one is a bar made by Kimberly Natures Art.

I am aiming only for a bit of added transparency, my main goal is to lower the melting point of the soaps. Most cured soap needs to be heated close to 200*F and cools very quickly. It also, as I've found, tends to melt your molds.

Transparent soap is not much more complicated but it takes more solvent. If you do not have a high ratio of stearic, palmitic, myristic or lauric acid in your soap the soap can get rather soft. In addition recipes with castor oil turn out much more transparent due to the fact that castor oil also acts like an alcohol.

Making re-batch MP is super easy. For your recipe you only need to weigh out your scraps and add 20% alcohol. That's it.. Really...
  • Put your scraps into a microwave safe container.
  • Microwave them with short 30 second bursts until the soap gets sticky.
  • Add some of the heated soap to your alcohol then pour that back into your container.
  • Microwave that with short 15 second bursts stirring after each burst.

Sticky Soap

Adding to alcohol

You will end up with a soap broth that looks similar to the following pics.

Notice the "new" melt point of the soap.

Here is how easily it pours.

Here are a few pics of the soaps setting up.

And the final bars. Remember I was only shooting for MP not transparency, but you can clearly see a shift into transparency in both bars.

I decided to see what it would take to make Kimberly's soap transparent. I used hers because I have already done this with my BDG soaps.

I used 40% alcohol and 5% more water this time and this is the result. A really nice and firm golden soap. The golden color came from the oleic acid that Kimberly used to make the soap.

I ended up using the extra water because the soap did not want to dissolve into the alcohol, instead it looked sort of like boiling oatmeal or taffy. I have found when this happens just a little bit of water is needed to correct this.

To learn more about soap making from Biodiesel glycerin, be sure to check out our great book "Making Biodiesel Glycerin Soaps". It contains lots of great tips & tricks for getting the best soap out of your Biodiesel glycerin. Click here to learn more.

Happy Soaping :)

Copyright Knice-N-Clean Soap Company LLC 2010 All rights reserved


  1. Hi - can you tell me what kind of alcohol you used to dissolve the rebatch soap? I'd like to try this. Very interesting techniques you have here.

    Kathy W.

  2. I sure can. I used ethanol in this example. Isopropyl would work too. I've also played with sorbitol and extra glycerin with some success.

  3. Thanks! With the sorbitol, did you use that instead of ethanol? Was this a combo of sorbitol and glycerin that dissolved the melted soap? I have noticed that most all commercially made M&P soaps have added glycerin, sorbitol, sorbitan oleate (a derivative of sorbitol), and some type of protein, either soybean or wheat, as a conditioner. I am trying to formulate my own M&P, so finding your blog has been most helpful!


  4. There seems to be a delay of several hours before I can see new posts, so I'm not sure if the last one just disappeared or if I'm being too impatient. Also, the "contact us" button gives me an error message - please tell me more about the sorbitol and glycerin version of this formula, and what you considered to be successful (and what wasn't.) Thanks for your help,

  5. Kathy,
    I too am working on a M&P base from our BDG. What I have found is that the sorbitol works as well or better than the ethanol. I have enough glycerin in my BDG. If the M&P has enough hardening ingredients the soap will stay hard. The sorbitol works to lower the melt point of the soap too. I have ordered some sorbitan oleate, but I hope that I will not need it. A 50:50 ratio of solvents to soaps seems to work well with the sorbitol/glycerin combo. Surprisingly extra water can help too. Another benefit to sorbitol vs ethanol is that the sorbitol will not evaporate out of the soap.

  6. Kathy,
    Are you shooting for just M&P or transparency as well?

  7. I would like to be able to formulate a transparent soap and an opaque soap, so the answer to your question would be, both. I just found a soap supplier who offers a "natural" M&P that lists the ingredients as saponified organic palm oils (includes stearic acid), organic palm glycerin, and water. In the description, it says that the soap will sweat a bit more that other M&P soaps, due to the high level of glycerin, which is 27%. So I am concluding that there are many ways to make soap into M&P soap: add ingredients that will act as a type of solvent, which makes the soap pourable and smooth in texture, and also lowers the melting point. And of course, the soap has to become hard when it cools, so that it can be used as soap. I'm also waiting for some sorbitan oleate to arrive, I think that it might have a nice contribution to the tactile properties. But that remains to be seen, or felt, as the case is here! Thanks again, I am really enjoying the exchange of ideas here. One last thought: if sorbitol works very well as a solvent, I wonder what else could be used as a solvent, too? I am trying to achieve a very natural product, and though some sorbitol is derived from corn or berries, I had a hard time finding sorbitol to purchase. This isn't a good thing if I formulate with sorbitol and then can't get it anymore.

  8. Transparent soap is going to require more hardening ingredients because you will need more alcohol to achieve transparency. We have the same issue with sweating with BDG because of the high ratio of glycerin. I get sorbitol in a 55 gallon drum from a local chemical company, maybe we could go in on a bulk buy or something. I think the sorbitol is key unless you use propylene glycol or ethanol. Both of which have their negative issues.

  9. I see that you are located in Michigan, I am in Texas. I may be interested in a bulk buy,if the shipping isn't too high and depending on how my experiments come out - that would be very helpful. Is the sorbitol in liquid or granular form? The sorbitol I bought (1.5 kg) is granular, I thought it would save on shipping because it's 100% sorbitol, and I wouldn't be paying for water. Do you make a solution in water before adding to the soap? Agreed on the PPG and ethanol, although for different reasons on each. The sorbitol really seems to be the answer for making good M&P. Thanks, Kathy

  10. Love the steps to my own soap making guide.Yours have come out brilliant and mine may not but yet the experience is going to be memorable.
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