Making bulk lye for multiple batches

Wondering if you can pre mix a bunch of lye then measure it out later, same day, for different soap batches all using the same lye/water ratio. Or by doing this will the lye to water ratio be off by just enough to mess me all up? If I have different recipes is the lye water ratio different or is it only different when you have varying amounts of oils being mixed? Now I am confusing myself

Yes- you can indeed premix your lye solution for use later later the same day, or even weeks or months later. That's actually the way I do it all the time.

I make a large (for me) quantity of 50% lye solution in a plastic PP #5 container with lid, and when it has cooled down I store it in an airtight HDPE container (actually a thoroughly cleaned-out, reclaimed detergent bottle with a no-drip spout and cover). As long as it is stored in a proper container and properly covered, it lasts for months.

The reason I like working from a 50% solution is because it's super easy to figure out the math that it takes to tailor it to use with any recipe no matter how big or small the batch, or what lye solution your formula calls for. To tailor it, I just use this simple 2-part equation, which works across the board with every formula no matter what:

How much 50% lye solution to weigh out for your batch: Total recipe amount of dry lye your formula calls for, multiplied by 2, equals how much of the 50% lye solution to weigh out for your batch.

How much extra water to weigh out for your batch: Total recipe amount of liquid, minus the total recipe amount of dry lye for your formula, equals how much more liquid to weigh out for your batch.

That's all it takes to figure it out. Easy-peasy.

Or by doing this will the lye to water ratio be off by just enough to mess me all up

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I'm glad you asked this because there is some slight evaporation that takes place when mixing the 50% solution. After my very first masterbatch in which I made sure to weigh everything from beginning to end (container/cover and all), I figured out that my water loss from the heat reaction during mixing came to 6 grams worth, i.e., it weighed 6 grams less than it should have (I just added 6 grams of water back in to compensate and all went well).

The size of my 50/50 masterbatch is a little over 4 lbs. worth, so as a result of my first experience, after having first weighed out my container and cover, I now weigh out 2 lbs 3.3 oz (or 1002 grams) of lye. And then I weigh out 2 lbs 3.6 oz (or 1008 grams) of water- a 6 grams excess. In the end, right when I get done mixing, I weigh my finished solution to see if it all adds up correctly (the weight should be 2004 grams if all went well). If it comes up short (which surprisingly has never happened yet with my subsequent masterbatches), I would just add more water at this time to equal 2004 grams, but so far, all has gone well and it weighs out 2004 grams - an even 1:1 ratio. When I go to weigh the solution later, after it has cooled off, it's still 2004 grams (I cover my container as soon as I'm done mixing).

I hope that made sense and that I didn't cause more confusion. Trust me, it sounds more complicated than it really is.

If you need me to clarify anything I said, just let me know.

HTH!
IrishLass

IrishLass is my sparkly soap hero

I've been using the method she posted for over a year now and its WONDERFUL!!! In fact, I have TWO 'Downy' softener bottles (Costco size) that I fill up on a somewhat weekly basis. Makes soaping lovely, a little less stressful, and casual.

I do this also.

]How much 50% lye solution to weigh out for your batch[: Total recipe amount of lye your formula calls for, multiplied by 2, equals how much of the 50% lye solution to weigh out for your batch.

So is that dry lye your multiplying by 2?
Would you also use the same formula if you were to make your own lye solution by running water through hard wood ash?

Your solution is 1/2 lye and 1/2 water. You look at your lye requirements and multiply that by 2 (to get 100% of your lye requirement but since more water is needed than lye, you will need to find out how much more to add) and that is how much total solution to measure out. Then you subtract the lye requirement from your water requirement and add the difference (in water, goats milk, etc).

I have no clue about making your own lye. I do not understand how you would test the lye solution to make it an accurate and usable product due to the variables possible in DIY lye.

tfelog said:

So is that dry lye your multiplying by 2?

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Yes- as Buckawww graciously clarified for me (thank you )- you look at what the (dry) lye requirements are for your batch, and then multiply that number by 2.

tfelog said:

Would you also use the same formula if you were to make your own lye solution by running water through hard wood ash?

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That is something beyond my knowlege since I have never made my own lye, but just so you know- lye made from wood ashes is a much different animal from the kind of lye I use to make my masterbatch solution. The kind of lye made from wood ashes is known as potash or potassium hydroxide, while the lye I make my solution from is sodium hydroxide. Potassium hydroxide is used for making soft soaps or liquid soaps, while sodium hydroxide is used for making hard or bar soap.

What kind of soap are you hoping to make?

IrishLass

This is probably a really dumb question, but Irishlass when you say you make a 50% lye sloution what do you mean exactly. Maths and numbers have never been my strong point so a really detailed explaination would help me no end. I really like the idea of being able to just pour out what is needed and it sounds such a good idea if only I can understand it correctly. Many thanks.

My apolgies as I have done further reading and you have already explained clearly how to make a 50% solution previously.

This is another question that is probably a bit stupid...

Preparing the lye solution in advance like this obviously has many advantages. I haven't tried it because I don't soap at room temperature, more like 35-40C. I am afraid that the soaps won't gel if I soap that cool. I assume the oils are cooled to RT as well. Is this a legitimate concern?

This is another question that is probably a bit stupid...

Preparing the lye solution in advance like this obviously has many advantages. I haven't tried it because I don't soap at room temperature, more like 35-40C. I am afraid that the soaps won't gel if I soap that cool. I assume the oils are cooled to RT as well. Is this a legitimate concern?

busybee said:

This is probably a really dumb question, but Irishlass when you say you make a 50% lye sloution what do you mean exactly. Maths and numbers have never been my strong point so a really detailed explaination would help me no end.

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Hi busybee- actually, it's a lot easier than it sounds on paper. Trust me. Simply put, a 50% lye solution just means a solution that consists of equal parts of lye and water. For example, if you want to fill up a 2004 g. storage bottle with 50% lye solution, you would need to dissolve 1002 weight of lye into 1002 oz weight of water (1002 + 1002 = 2004). Since 50% of the solution is lye, and 50% is water, we call it a 50% lye solution.

Now, if you attempt to try this, you need to bear in mind that lye needs at least an equal amount of water in weight to be able to dissolve properly. In the above example, mixing 1002 g. of lye with 1002 g. of water sounds perfect- equal parts of lye and water. On paper it looks great, but when actually mixing the two, a lot of heat is generated and some of the water is evaporated off and things aren't so equal anymore- there's slightly more lye than water. Good news, though- you'll be able calculate exactly how much water has evaporated off and add it back in if you were careful to write down the weight of everything beforehand, i.e. your empty mixing container and cover, as well as the lye and water, etc.. and compare the end weights.

To explain-

Let's say these are your weights (well, these are my own weights, actually):

Lye 1002 g
Water 1002 g
Empty container with its cover on 244 g

When all is said and done in a perfect scenario with no evaporation, at the end of mixing, my lye + water +container w/cover should equal 2248 g. But it weighs out less than that at 2242 g at the end of mixing.

2248 - 2242 = 6, so I have a loss of 6 g of water. No problem- I weigh out 6 g of water and add that back in. Voila- all is well again!

Nowadays I just add the extra 6 grams of water in at the beginning (while still comparing weights at the end), and so far (to my surprise), my end weights are a perfect 2248 on the nose. I don't take that for granted, though- I still weigh everything anyway just in case.

I hope that helped to clarify things better. If not- don't be afraid to ask.

IrishLass

fiddletree said:

This is another question that is probably a bit stupid...

Preparing the lye solution in advance like this obviously has many advantages. I haven't tried it because I don't soap at room temperature, more like 35-40C. I am afraid that the soaps won't gel if I soap that cool. I assume the oils are cooled to RT as well. Is this a legitimate concern?

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fiddletree- not stupid at all. It's a very valid question. Like you, I don't soap at room temp either, and I like my soaps to gel. As a matter of fact, I soap much warmer than you at around 50C because of the particular hard fats I use.

After weighing out how much 50% solution I need for my batch and adding the appropriate amount of water (I usually soap at a range of 33 to 40% lye solution rate), I cover my container and place it in a hot water bath- just a bowl filled with piping hot water- and I let it sit there while my fats are heating up. I soap when my fats have reached temp and my lye solution is warm (not hot) to the touch. I haven't measured it, but I figure my solution is probably about 38C to 40C- a little warmer than body temp.


IrishLass

Irishlass thank you so much for your answer, it is very much appreciated.

I just now read all this info, and I have to say, WOW thanks! I also have to say, what? I understand how to make the 50% lye buuuut am lost when I want to mix lye at 34%. Hmm, now that I am writing this I think I am seeing it clearer.

OK, bear with me, I am no good an explaining my thought process

So I soap with 34% lye. Since my premix is at 50% lye I will need to add more liquid, water, milk, aloe, whatever, to reduce the % of lye in my mixture down to 34%. So say I need 100g (keeping it simple so I can understand this) total of lye and water. Would I measure out 84g of 50% lye and add 16g of liquid to it??? :shock: Oh my, I am such a visual learner, this is tough for me.

How did I do? Did I fail?

I just reread your instructions and had my ah ha moment. AWESOME! Thank you so much for this valuable information. I have a few people wanting many bars of soap. My back stock has dwindled and I need to soap like crazy this week. This will make life much easier!

IrishLass you are awesome Thank You!

I master batch my lye and I usually soap at a 33% lye solution (2 parts liquid to 1 part lye).

The math on this could not be more simple.
When you calculate your recipe simply swap the lye and water amounts (use the water amount for your 50/50 lye solution measurement and use your lye amount for your water/add'l liquid measurement). Trust me... it works out. Since your 50/50 solution already has one part water and one part lye, you just need to add one more part water.

serfmunke said:

I just reread your instructions and had my ah ha moment. AWESOME!

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Cool beans! You're going to love masterbatching your lye solution. It cuts down on the biggest hassle (at least for me) of soap making.


IrishLass

Oh boy does my brain hurt right now! I think I got it but I'll have to read everything again to make sure. This sounds great! I'm going to have to definately try this.

So for those of you who premix your lye, do you premix your oils also? I know someone on YT that does that from her videos and was always wondering if that even works and if you get the same result all the time. Anyone?

IrishLass said:

serfmunke said:

I just reread your instructions and had my ah ha moment. AWESOME!

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Cool beans! You're going to love masterbatching your lye solution. It cuts down on the biggest hassle (at least for me) of soap making.


IrishLass

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I am excited but have to wait for my laundry detergent to run out. I ran downstairs to see how much was left, very little and I have a mountain of laundry to do! Never have I been more excited to do laundry

Thank you again!

serfmunke said:

I am excited but have to wait for my laundry detergent to run out. I ran downstairs to see how much was left, very little and I have a mountain of laundry to do! Never have I been more excited to do laundry

Thank you again!

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Any time!

FOhoarder said:

So for those of you who premix your lye, do you premix your oils also?

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I kinda do, but not on a consistent basis or on a scale that would be considered large by any means. If I were living with the constraints of running a soap business, I most probably would, though. I've read of many soapers in business that premix their oils, but I'm still quite content swimming around in the pressure-less waters of the happy hobbyist stage yet. The most premixing of my oils that I do (if I have the time and am inclined to do so right then at that very moment :wink: ) is to pre-weigh out my oils in one container and my hard fats in another for 2 or 3 batches at a time that I know I'll be making over the next few days or so. Other than that, though, I just weigh as I go. But not so with my lye solution. That's much more of a hassle for me to mix fresh each time, what with all the safety precautions needed and making sure my mixing area is clear of people and keeping the fumes at bay, etc... so the less I have to go through all that rigamarole, all the better.


IrishLass