How much water to use when BDG soaping.

The three basic methods of determining water in traditional soaping are;

• Water as a percentage of oils. 20% - 40% for traditional soaping.
• Lye concentration 20% - 30%
• and water:lye ratio usually 2:1 for NaOH and 3:1 for KOH

You can short the water as low as a 1:1 lye:water ratio.

Shorting water for bar soap can be tricky. Shorting water for Liquid soap may be unnecessary, in fact adding more water can be beneficial.
How do we apply this to BDG?

Let's talk bar first.

If your soap:glycerin ratio is low in soap then you can get away with shorting the water a bit more. The higher the soap ratio the harder it is to short the water, especially if you will be hot processing (HP). If you will be cold processing the soap you can get away with shorting the water because you can pour the soap prior to the soap getting too thick. If you will be adding additional ingredients to your bar soap and are going to short the water you will want to be sure to cold process (CP) your soap.

I will be modifying the calculator to allow you to adjust your water method. Overall if you are not going to HP your soap shorting the water is okay especially if you are not going to add other ingredients. When you start adding other ingredients you may find it more difficult to short the water.

You might think that the fact that our BDG is very low in saponifiable elements makes things easier, but in some ways it makes things harder. It's easier because the soap that exists helps "seed" new soap formulation, however the soap has a much higher melting point than the oils. That's one reason I talk about the 170*F - 180*F as cold processing (CP). Normal CP soaping is around 110*F - 160*F. CP in this case means that the soap is not cooked until it is neutral, and no additional heat is used after trace.

If you use too little water when making BDG bar soap you could actually end up with little caustic pockets instead of saponifying the BDG. 5% - 10% of the weight of your BDG should be sufficient to keep the BDG fluidic when making bar soap. The extra can also improve the workability during saponificaion and should evaportate out during the curing phase. Another ingredient than can improve workability is sodium lactate, so much so that we have actually included it as an optional ingredient in bar soap recipes generated with the soap calculator.

Now for liquid soap.

All of this holds true for liquid soap too. The soap will end up as a paste that you later dilute into liquid soap. With that we can also use a pre-diluted method where the soap has some of all of the water for the final dilution added during saponification. This avoids the need to dilute the paste later but some of the water can evaporate during the cooking phase of HP. You can weigh the soap before and after to make up the difference. One advantage of the paste method is that you need less space to store the excess soap. One advantage of the pre-diluted method is that it is much easier to add the final dilution water.

If you will not be adding any extra ingredients you might want to add more water than the caustic calls for. This is because you have already demethed and "dried" the BDG. If the BDG gets too thick for your stick blender when you add the caustic water, you might think about adding enough water to allow the BDG to remain fluid.

Conclusion -
As with traditional soaping deciding how much water to use can be tricky. You will have to decide for yourself how much water to use and when to short the water.  Liquid soap is much more forgiving than bar soap when it comes to water.

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