new12soap said:
IrishLass said:
I'm one of those that makes my own pre-mixed lye solution to use at home, but since I'm the one making it, I'm always in-the-know of how much water is in it.
IrishLass
IrishLass, I would like to use a premix when possible. How much do you mix at a time? In what and where do you store it? Will any old HDPE plastic jug with a lid work? For how long will it keep? And how do you calculate how much to use? I know there is a place on soap calc for solution, but the recipe still lists both water and lye, do you add those numbers together and use that much solution? TIA
I make a masterbatch/pre-mix of 50% lye solution (50% water/50% lye). A 50% solution works perfectly for me because the math is very simple to calculate when it comes to figuring out how much solution to weigh out for my batches, no matter if I want to soap a pure Castile with a 40% lye concentration or an HP batch with a 28% lye concentration, or 33% for the rest of my batches. Working from a 50% solution makes that very easy for me with a simple, 2-part equation (which I'll give you in a moment's time).
I mix enough 50% solution for making 7 or 8 batches in a large Rubbermaid container made of PP #5, and when it has cooled I then pour it through an SS strainer into a reclaimed laundry detergent bottle made from HDPE #2 (the kind with one of those no-mess pouring spouts that catches drips and forces them back inside the bottle), with a tight-fitting cover.
The solution lasts for months. I've done experiments with my pre-mix by using it as far as 8 months down the road and all my batches came out perfectly fine with nothing weird or unusual going on.
And how do you calculate how much to use? I know there is a place on soap calc for solution, but the recipe still lists both water and lye, do you add those numbers together and use that much solution? TIA
If you are working from a pre-mixed 50% lye solution and you want to soap your batch at a 33% concentration/solution, or a 28%, or whatever % you want to soap at, go ahead and type your particular % of choice into the Lye Concentration box on SoapCalc (totally ignore the 'Water as % of Oils' button-for that button is irrelevent when soaping from the Lye Concentration box), and then enter your recipe as you'd normally do. When you click on 'View or Print' and see the lye and water amounts, conduct the following simple 2-part equation in order to know how much of the 50% solution to weight out (this same equation will work for every batch no matter what solution % you want to soap with- just as long as your pre-mix is a 50% solution):
Lye x 2 = how much of the premixed 50% solution to weigh out.
Water - lye amount = how much extra water to add.
For example, let's say you want to soap your batch with a 33% lye solution and SoapCalc shows the lye amount for such a batch comes to 6.7 oz, and the water amount comes to 11.8 ounces.
6.7 (lye) x 2 = 13.4 oz of your premixed 50% solution to weigh out.
11.8 (water) - 6.7 (lye) = 5.1 extra water to add in order to turn the 50% solution into a 33% solution.
Now, when preparing the pre-mixed 50% solution, some things need to be taken into consideration when making it, such as evaporation. Please see this thread which explains how I go about making my pre-mix:
http://www.soapmakingforum.com/forum/vi ... asterbatch
HTH!
IrishLass