Lye Master Batch: How to Make and Its Application

I will be out of town the next couple of weeks.  It will be a reluctant break from my soapmaking mania, but I am excited to be in Honolulu for the Hawaii Food and Wine Festival and to be visiting my sister in California after. Yipee!!!

Before I take off, here’s a tutorial on lye master batching.

LYE MASTER BATCHING, 1:1 ratio or 50% concentration

1.  You will need:

• 2 liters distilled water
• 2 kilos sodium hydroxide/NaOH/caustic soda (pearls or flakes)
• 1 chemical-resistant plastic container* that can hold 1 gallon or minimum 3 kilos
• 1 large bowl or basin that can hold the plastic container
• 1 digital weighing scale
• 1 pair gloves
• 1 pair safety goggles
• 1 long chemical-resistant stirring spoon

*To learn more about what’s safe to use, you may want to check out this forum thread. Avoid metal containers as you run the risk of turning your lye solution gray, and always have a container with a bigger capacity than what’s going into it.

2.  Although you can mix the solution in the kitchen with the exhaust turned-on, I prefer to do it outside for better ventilation as the fumes are very biting and strong.  Just for added precaution so that the lye solution does not overheat, I always place the mixing container in a bowl filled with cold tap water (think nuclear reactor). With safety gear in place, it’s time to pour the NaOH into the container with distilled water.

3. Cover your nose (I just hold my breath) and stir until the NaOH has been completely dissolved.

4. Cover the container loosely to prevent debris from going in and to prevent rapid evaporation. If I make the lye solution before going to work, I transfer it to a bathroom that no one uses.  By the the time I come home, it would have cooled down already. Alternately, this can be done at night and left to cool down overnight.

Right after mixing, the solution gets very very hot, near boiling.  Look at the water bubbles forming from the heat:

5. When the solution has completely cooled down, give it a good stir. I also like to strain it before it goes into the jug. Make sure to clearly and properly mark your container and store in a place where no one will accidentally bump into it or mistake it for something else.  (I store it under the kitchen sink)

The net weight of the solution is 4 kilos or 8.8 pounds, but since the solution is very dense, its volume is approximately a little over half a gallon.

HOW TO USE 50/50 MASTER-BATCHED LYE IN YOUR RECIPE

To avoid confusion, I will be using the term lye pre-mix to mean master-batched lye solution and NaOH to mean DRY lye or caustic soda.

Let’s take an example and assume these were the numbers shown after running your recipe through a lye calculator:

                  Water 265 grams          NaOH 130 grams

→ Multiply the called for NaOH by 2:

                 130 g. NaOH x 2 = 260 g. lye pre-mix

→Subtract NaOH weight from water amount (lye calculator amounts):

                 265 g. water – 130 g. NaOH = 135 g. additional liquid

(Explanation: Remember our lye pre-mix is half water, half NaOH. Thus, to determine how much pre-mix to use, we have to double the NaOH quantity called for in the recipe.  Correspondingly, we have to deduct the water in the pre-mix from the total liquid required to know how much more to add.)

In a nutshell:

A recipe that calls for 130 grams NaOH and 265 grams water would need:

                 260 g. lye pre-mix + 135 g. water

To double check that your conversion is correct, the sum of the numbers of the original recipe should be the same as for the pre-mix:

Original recipe:            265 g. water + 130 g. NaOH = 395 g.

Recipe with pre-mix:   135 g. water + 260 g. lye pre-mix = 395 g.

Note: Mixing the lye pre-mix with additional water or any form of liquid will cause the whole thing to heat up again!  Unless you actually prefer to have it hot to melt hard oils or for whatever reason, I suggest mixing your water/milk/juice directly into the oils, then adding in the lye pre-mix after.

I hope my tutorial was clear and didn’t make you more confused 🙂 .  For additional information, there are several forum threads out there, just google “lye master batching.” I would also highly recommend reading Kevin M. Dunn’s Scientific Soapmaking.  From his book, I learned it was possible to have a 50% lye concentration, and even though it does not talk about master batching, it helped me to understand lye and water percentages/discounts and just about all the nerdy stuff behind soap making. (Ok, there was a lot of hard core chemistry and equations that I skipped. I only read portions that interested me 🙂 )

I don’t master batch my oils because I like playing with different recipes, but I can’t imagine going back to weighing and mixing lye every time I have to make soap.  I just love the ease and convenience, and in my opinion, it’s really no more dangerous than having to dissolve solid NaOH every time.  Needless to say, extra precaution has to be taken when dealing with any hazardous substance.

When I need to use some lye pre-mix, I just pour directly from the jug. I don’t even shake it because I think the the NaOH has dissolved and bound completely with the water. But that’s just me.  I guess there’s no harm in shaking it up a bit before using, if that makes you feel better.

Happy soaping! 🙂