Solubility of NaOH in Cold Water?

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BrewerGeorge

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I know that the generally accepted number for lye solubility is 50% - ie, if I want to dissolve 160g of NaOH, I need at least 160g of H2O to do it. But what about when temps are lower?

I made CP last night, and in attempt to speed things and soap cool, I added the lye to ice (RO ice) rather than liquid water at a 30% lye concentration. Latent heat of fusion being what it is, everything was liquid and cloudy at about 74F, at which point I added my adjuncts - sugar, salt, and sodiums citrate and lactate. Gave everything a stir and set it aside as usual while I prepared my fats.

But when I came back to the lye a few minutes later there were solids at the bottom. Chunky solids. But they felt kind of "soft" with the spoon and looked like sugar. I buzzed everything (carefully!) with the SB and set it aside again while preparing colors and scents. It seemed good when I got ready to pour, but I decided I should strain this one rather than just pouring the way I usually do.

Aaanndd... crap! There's a not insignificant amount of solids in the strainer. But it still looks more translucent like sugar than white like lye, and I'm past the point of no return so I put the strainer in the sink and carry on. I'm only going to light emulsion, but everything seemed to progress normally. (That Lilac FO I was so worried about was an absolute *****cat with over 60% of fats from OO, lard and avocado soaped at 110F. It was actually too loose going in the mold after the ITP swirl, costing me color definition I'm sure.) It seemed to be gelling when I checked on it before bed.

So what are the chances I've made a very over-fatted soap? Is 30% lye concentrate soluble at 74F?

ETA: Obvious lesson learned never to use only ice again. Next time I'll use water equivalent to the lye and make up the difference with ice.
 

dibbles

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Your sugar should be dissolved in the water before adding the lye. I found that out the hard way, and the first time I used sugar, adding it to the lye water, I had exactly what you are describing happen. I squished and stirred and squished and stirred with a spoon until it finally (mostly) dissolved and strained. In your case, using ice for part of the water to mix the lye, the sugar could be added to the other liquid portion.
 

BrewerGeorge

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Your sugar should be dissolved in the water before adding the lye. I found that out the hard way, and the first time I used sugar, adding it to the lye water, I had exactly what you are describing happen. I squished and stirred and squished and stirred with a spoon until it finally (mostly) dissolved and strained. In your case, using ice for part of the water to mix the lye, the sugar could be added to the other liquid portion.
I barely used ANY water - just enough to make the final adjustment to get the exact amount of total water. I won't make that mistake again, you can be sure.
 

dibbles

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I barely used ANY water - just enough to make the final adjustment to get the exact amount of total water. I won't make that mistake again, you can be sure.
Live and learn when dealing with soap - I should write that on the wall over my soaping table.
 

shunt2011

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I agree with dibbles, you need to dissolve your sugar and salt and maybe even your citrate (I've not used it yet) in water before adding to your lye mixture if you are using frozen water/milks with your lye. Otherwise you will get undissolved bits in the bottom. Others have had this happend.
 

DeeAnna

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Yep, ditto what Dibbles and Shari said. Been there done that. Sugars and salts (SL, table salt, citrate) need to go into plain water, not lye solution. Two things going on -- the sugars are chemically reacting with the lye and the salts can be affected by the difference in solubility in plain water vs lye solution. If your lye solution was properly dissolved before you added the extras, it would not precipatate back out of solution. The goopy parts were clumps of partially reacted sugar.
 
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penelopejane

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Checked at lunch and it looks like soap. Still too soft to unmold, but it's still warmer than ambient, too. A couple more days, I guess.

I found even if I mix salt and citric acid with equal lye and water (so 1/2 water) it still precipitated out some. I use a purer salt now but I also now mix all the additives with a tiny bit of water to dissolve and then mix them with the milk. I thaw my milk (I store it frozen). Then I add my milk to the batter, stir in really well, then add the lye. It all stays dissolved and doesn't burn the milk.

I find it difficult enough to keep the lye alone dissolved in 1/2 water and find I have to stir really well at the start and keep an eye on it.
 

Arimara

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Would it be better to make a 50% lye solution and use the remaining water to separately dissolve salt and sugar for the soap?
 

lenarenee

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My experience (for what it's worth) is that sodium citrate is the most difficult to dissolve well compared to sugar and salt and lye. Now, the type of salt also makes quite a difference: regular table salt dissolves better than high mineral content salt like Himalayan salt - even in warm water.

I've used sodium citrate in all my batches for the past year and find that it's quicker to fall out of solution compared to salt and sugar. It's the slowest to dissolve. I save a small portion of my water percentage out, heat it, then add the sodium citrate, stir often, and give it a good 15 - 30 minutes before using it. If using room temp water - I give it and hour and lots of stirring.

What kind of lye do you use? I have microbeads, and used ice and ice water for the lye solution and dissolving was not a problem. Hopefully, your lye was dissolved, and the sodium citrate was more the problem.
 

penelopejane

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Would it be better to make a 50% lye solution and use the remaining water to separately dissolve salt and sugar for the soap?


The reason I am using 50% water is because the other 50% of the liquid is goats milk. That's why I add my salt and other additives to a small amount a reserved water, mix that with the GM powder I hear the water a bit to dissolve the GM powder more easily and then I mix in the GM. Mix it all together with the oils and finally add it to the lye.

So much more fiddly than "normal" soap. Not sure GM is worth the effort!
 
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Susie

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Are you using GM liquid AND GM powder, or using GM powder mixed with water for all the GM?
 

Arimara

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Honestly, I was asking a general question. It just seemed to make more sense to have a cup with sugar water mixture or simple syrup for ease of use, another cup with a little salted water and the rest of the liquid is the lye solution.
 

The Efficacious Gentleman

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It all depends! As so many things so often do, let's be honest.

If you master batch or want to do a split method, you have a 50% lye solution. That in itself is stand alone, utterly saturated, done and dusted. So we need to look elsewhere for dissolving our 'additionals'. With milk etc, I have made less of a 50/50 split and more of a 50/40/10 split, with the 50 being the lye solution, the 40 being the milk and the 10 being the carrier for the other additives. Of course, the exact amount of the "10" will depend on your additives (not everyone will take sugar when using milk, as the milk has sugar. Same with SL, as the milk has lactose.................) but essentially you need your 50% lye solution, then enough liquid with your additives dissolved and then your milk.

As Penny said, you could take your 50% lye solution and taking in to account the plus and minus of it all, you could take the other 50% water and add in the additives AND the milk powder. As long as all of the water can take all of the things that your throw at it, it would be okay.

As for whether or not milks are needed..............someone did a blind test of body bars and the results showed that milks didn't make a noticeable difference. I made batches of my shaving soap with and without milk, and I noticed a difference.

As I often say, you can't have your cake and eat it when it comes to soaping. So try different things and find out what is an absolute must have and then you know what you need to do.
 

BrewerGeorge

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Well, I think there's something a bit wrong with this soap. Super-soft, but I could cut it. I'm going to give it a few days to harden up before judging, but it just looks and feels wrong somehow.
 

snappyllama

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Would it be better to make a 50% lye solution and use the remaining water to separately dissolve salt and sugar for the soap?
That's what I do... I keep my lye solution around 60% water to 40 % lye. The rest of my water goes into an additive slurry (with EDTA, milks, powders, SL, whatever) that I combine really well with my minifrother and then add directly to my oils. Then I stickblend that and add my FO before finally adding my lye solution to it.
 

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