Is it wrong to calculate Lye like this?

[Fernando Sage]

I was going to make 3 different kind of soap, all CP just different scents and colors so I calculated the total amount of fats, total of water and total of lye.

I melted all the fats for the 3 soaps together.

Combined the total lye with the total water which was:
Water: 21.74oz
Lye:12.79oz

Technically I would end up with 34.53oz of lye solution.

So for the first recipe I added the water+lye amounts indicated on Soap Calc (water 8.85+Lye 5.2), which was 14.05oz and poured that exact amount from the total solution.

Did the same for the second.

Turns out, for the last soap I was short 0.9oz of lye solution.

Does the chemical reaction between lye and water reduce the total mass?

by the way here‘s some extra info:
Superfat - 0%
Water: Lye ratio 1.7000:1

I calculated the % of lye solution I was short (not much) and reduced the same % from the fats .

Does that make sense? Or I won’t be able to use my soap ?
Or should I have left the extra fat as a higher super fat?
Is there a chance my soaps are going to be lye heavy?

I had never done that, I always prepare the lye solution needed for each separate recipe.
I thought I would be saving myself some time by preparing the total lye solution I would need.

The more I make soap the more I realize I still have a lot to learn

 

[dibbles]

It's fine to prep all your oils and lye solution for multiple batches. I suspect that some of the water evaporated from the lye solution due to the high temperature. You probably wouldn't notice it as much with smaller amounts for a single batch. If you make multiple batches like this again, weigh your container so you will know how much water was lost, and add that back into the lye solution before mixing with the oils.

If you are sure you weighed everything correctly, I think your soap will be fine. If you are concerned that the soaps could be lye heavy, do a zap test to be sure.

 

[Fernando Sage]

It's fine to prep all your oils and lye solution for multiple batches.

Thank you! Sometimes we make 4/5 different types of soap and it’s quite a pain in the neck to measure everything separate for each recipe.

I suspect that some of the water evaporated from the lye solution due to the high temperature.

I suspect the same, but that means the there was more lye per oz of solution than expected because the solution got a little more concentrated than initially estimated, makes sense?

You probably wouldn't notice it as much with smaller amounts for a single batch. If you make multiple batches like this again, weigh your container so you will know how much water was lost, and add that back into the lye solution before mixing with the oils.

That is the tip that I needed today, to add water back into the solution to keep the expected concentration!
So obvious and yet here I was thinking how would I calculate what’s the ”new concentration” after evaporation.

Thank you so much!

 

[KiwiMoose]

Hola Fernando! You have done what we call 'masterbatching' with your lye and water. A lot of people on here ( not me) make up significant amounts of lye solution ahead of time so that they can use it straight from the bottle without having to measure it each time. Do a search for it on the forum - it sounds like it might be useful for you.

 

[Fernando Sage]

Hola Fernando! You have done what we call 'masterbatching' with your lye and water. A lot of people on here ( not me) make up significant amounts of lye solution ahead of time so that they can use it straight from the bottle without having to measure it each time. Do a search for it on the forum - it sounds like it might be useful for you.

I feel like such a pro now that I know that what I’ve done had a name.

Masterbathcing sounds like a pro move.
Thank you so much, I’ll research more about it.

But why’s is it that you don’t do?

 

[dibbles]

Not @KiwiMoose but I don’t masterbatch either. I freeze distilled water and aloe juice and use that to make my lye solution. I make the lye solution first and by the time my oils are weighed and warmed and any additives or colors are prepped it’s usually ready to go.

My soaping space is in my basement, and during the winter months it can get pretty chilly down there. I’m afraid it could be cold enough that the lye could precipitate out of the solution. You wouldn’t have that problem in Miami

 

[dmcgee5034]

@Fernando Sage - I love love love masterbatching both my lye solution and my fats! Game changer!

I do my lye 50/50 with aloe vera juice that I keep cold in the fridge. I use a pound of lye 454g and 460g of AVJ to account for any liquid loss. This makes about 3 batches worth for my 1005g fats molds. I actually have a fresh batch cooling now. I keep 2 containers going so I don’t run out. If you do this, make sure your container is lye safe, and I always make it with the container sitting in a secondary container inside the sink. I’ve been using 2 pound lye containers from BB, and it’s been perfect!

For my fats, I make a batch that is about 6060g, Then I weight it out into containers that are 1010g - just over my batch size - to account for anything that I can’t get out of the containers. I’ve also left the big batch in my 3 gallon bucket with a lid, but I find it’s easier to just portion my batches out.

So much more time for design and creativity when I’m soaping.

 

[KiwiMoose]

Not @KiwiMoose but I don’t masterbatch either. I freeze distilled water and aloe juice and use that to make my lye solution. I make the lye solution first and by the time my oils are weighed and warmed and any additives or colors are prepped it’s usually ready to go.

That's exactly what I do @dibbles!
I don't know why I don't master batch - possibly because I always add something else to each batch ( oat milk, rice water, coconut cream, aloe...) and I find it easy to work with these additives on a case by case basis. Some times I will use the additive as all my water content, sometimes only half, etc.

 

[Georgeandstella]

Hola Fernando! You have done what we call 'masterbatching' with your lye and water. A lot of people on here ( not me) make up significant amounts of lye solution ahead of time so that they can use it straight from the bottle without having to measure it each time. Do a search for it on the forum - it sounds like it might be useful for you.

So in concept, if the water in the master batch evaporates, then there is more lye concentration in the batch? Or is this 1: negligible or 2: minimal evaporation in lye safe containers so not a consideration (such as liquid detergent containers) ? Thank you

 

[DeeAnna]

Mass does not magically disappear when you mix up lye solution.

The 0.9 oz loss was most likely caused by residues of lye solution left in the container as well as some loss due to mist escaping from the hot lye solution when it is first made.

Lye solution, once it cools and is no longer forming mist, does NOT evaporate. If anything, the lye solution we make for soap is concentrated enough it will ABSORB water from the open air over time. This is also true of solid NaOH if it's not stored in a sturdy air-tight container -- solid NaOH will increase in weight over time as it absorbs water from the air.

The only time a container of lye solution will lose weight is when the lye solution is steamy hot. At that time, mist will form in the air above the solution. The mist is NOT just water -- it is small droplets of actual lye solution. You want to lightly cover the container of hot steamy solution and you also want to avoid putting your face above the container -- don't expose your skin and respiratory system to this mist.

 

[TheGecko]

1) Does the chemical reaction between lye and water reduce the total mass?

I calculated the % of lye solution I was short (not much) and reduced the same % from the fats .

2) Does that make sense? Or I won’t be able to use my soap ?
3) Or should I have left the extra fat as a higher super fat?
4) Is there a chance my soaps are going to be lye heavy?

I had never done that, I always prepare the lye solution needed for each separate recipe.
I thought I would be saving myself some time by preparing the total lye solution I would need.

The more I make soap the more I realize I still have a lot to learn

1) Yes and no. "Yes" - When using a room temperature liquid, your Lye Solution will heat up to 200F-225F which creates steam. "No" - But because the temperature starts to drop once the NaOH is dissolved, it's generally not enough that you would lose almost an entire ounce.

2) Yes it does. See below

3) Depends on the size of the batch. For a 2lb batch of soap, 0.9oz of a 37% Lye Concentration is going to result in a softer soap. For a 25lb batch...not so much.

4) Since I wasn't there to witness the many possibilities of why you were short 0.9oz on your third batch, it is hard to say.

I'm starting my 5th year of soap making...I'm still learning. I don't think you can do anything and still not learn something new no matter how long you have been doing whatever the thing is...even if it is just a new tweak.

There is nothing wrong with your process, you just need to be more careful in your overall weights. If you say, need a total of 50oz of Lye Solution...you might want to reweigh it after it cools down to make sure you still have 50oz and add a little extra water to account for the loss through steam. When you weigh out the Lye Solution for the first and second batches, again you want to be careful that you are spot on. If you need 14.05oz, you want to make sure that you only weigh out 14.05oz and not 14.5oz.

I Master Batch both my Oils/Butters and Lye Solution, but not with any specific intent. I have a big bucket that holds 50lbs of Oils/Butters and two one-gallon jugs for my Lye Solution. I have a spreadsheet that lists all of my molds and how much Oil/Butter, Lye Solution and FO it takes to fill the mold. When I go to make soap I consult my spreadsheet for the mold I am using, weigh out my Oils/Butters, Lye Solution and FO and make soap. When I get near the end of the bucket, I transfer what is let to a small bucket and mix up another 40lb batch and when I empty one of the gallon jugs, I mix up another.

Since my recipes is 40% Soft Oils, the Hard Oils never fully harden and I use a commercial paint mixer on a drill to stir up the batter before each soap session. It takes about 30 second per pound of oils to melt and while the microwave is doing its thing, I'm weighing out my Lye Solution and FO and dispersing my colorants.

 

[KiwiMoose]

So in concept, if the water in the master batch evaporates, then there is more lye concentration in the batch? Or is this 1: negligible or 2: minimal evaporation in lye safe containers so not a consideration (such as liquid detergent containers) ? Thank you

The experts have answered - but I will just note here for reference (because this took me sooooooo long to understand when I started soaping) that if the lye concentration is reduced - it means that there is slightly more water to lye. If the lye concentration is increased, it means there is slightly more lye to water. It does NOT affect the amount of lye to oils that is required (assuming this was calculated correctly in the first place).

 

[cmzaha]

As some here know I masterbatched my lye for years and as DeeAnna noted I lightly covered the buckets I made my master batch in with a light microfiber cloth. Since I used 1-2 gallon buckets for my masterbatch it would get quite hot so I did not want to cover it tightly as that was not at all safe to do. My masterbatch was 50/50 and if I wanted to add in goat milk or other liquids I either used dry or just used it as the other 50% liquid needed for my batch. If I wanted aloe I would just mix a batch of masterbatch with a gallon of aloe juice from Walmart.

EDTA: my hdpe buckets I masterbatched in were also in a sink of ice and water to help with cool down since it would generate so much heat, and safety precaution if the bucket decided to leak. Fortunately, that never happened but there is always a first time.