Master batches lye

[violets2217]

I master batched for the first time with a small amount of lye I had left before I ordered more lye a couple weeks ago. About 30oz of 50/50 lye/water. Just went to use it and I guess I wasn’t using it often enough or it needs stirring every once in a while? When I went to pour some for a small batch I heard something knocking around inside and it appears something has crystallized in the bottom of the container. What did I do wrong?

 

[AliOop]

I master batched for the first time with a small amount of lye I had left before I ordered more lye a couple weeks ago. About 30oz of 50/50 lye/water. Just went to use it and I guess I wasn’t using it often enough or it needs stirring every once in a while? When I went to pour some for a small batch I heard something knocking around inside and it appears something has crystallized in the bottom of the container. What did I do wrong?

Usually that means one of two things:

1. All of the lye wasn't completely dissolved when you first mixed it, and it has settled out and crystalized, or

2. Enough water evaporated off to leave less than 50% water, allowing some of the lye to precipitate out and crystalize. If you know how much lye and how much water were mixed, you can weigh the total solution now to see if some water has evaporated. If so, you can try adding a bit more water, which causes the solution to warm up a bit - maybe enough to dissolve the crystalized lye.

TBH, I haven't had any luck with getting crystalized lye to dissolve later; I have always had to strain out the lye chunks. If you weigh them, you can get a pretty close idea of the remaining lye concentration. Or just wing it and make your soap with a bit of extra super fat to be sure. Or pour it down a slow-moving drain.

 

[violets2217]

Usually that means one of two things:

1. All of the lye wasn't completely dissolved when you first mixed it, and it has settled out and crystalized, or

2. Enough water evaporated off to leave less than 50% water, allowing some of the lye to precipitate out and crystalize. If you know how much lye and how much water were mixed, you can weigh the total solution now to see if some water has evaporated. If so, you can try adding a bit more water, which causes the solution to warm up a bit - maybe enough to dissolve the crystalized lye.

TBH, I haven't had any luck with getting crystalized lye to dissolve later; I have always had to strain out the lye chunks. If you weigh them, you can get a pretty close idea of the remaining lye concentration. Or just wing it and make your soap with a bit of extra super fat to be sure. Or pour it down a slow-moving drain.

I decided to clear some drains around the house. I’ll make sure to mix more at the beginning. I really liked having the master batch on hand.

 

[AliOop]

I decided to clear some drains around the house. I’ll make sure to mix more at the beginning. I really liked having the master batch on hand.

That was probably the most stress-free solution. I also love master-batched lye and will probably never go back to making it batch by batch. So nice to measure and mix, no waiting for cooling!

 

[violets2217]

So nice to measure and mix, no waiting for cooling!

EXACTLY!

 

[DeeAnna]

"...Enough water evaporated off to leave less than 50% water, allowing some of the lye to precipitate out and crystalize. ..."

A room temperature 50% solution of NaOH and water will absorb water from the air until it's in equilibrium with the humidity in the air. You'd have to live in the driest part of the Mojave Desert to see a 50% NaOH solution lose water to the open air.

If you don't believe me, find out for yourself. Measure a few grams of dry NaOH into a lye safe container. Set the uncovered container in a safe place in the open air. Wait an hour. You'll most likely see a liquid in the container at this time, not dry granules. Find the weight of this liquid. Is it double the original weight of dry NaOH? Wait another hour and find the weight of the liquid now. Is it more than double the dry weight of NaOH? Repeat until the weight stabilizes. Calculate the lye concentration at this point and you'll know the concentration where the lye mixture won't absorb or lose water at a given relative humidity.​

The more likely reasons for the solid lump of NaOH -- the NaOH wasn't completely dissolved to begin with or the NaOH solution got too cold (unlikely in Florida, I'd guess!).

Another possibility to explain solids in an NaOH solution is sodium carbonate settling to the bottom. But sodium carbonate typically forms a powdery layer that can be easily mixed into the solution. In my experience, it never makes a hard large lump.

 

[ScentimentallyYours]

"...Enough water evaporated off to leave less than 50% water, allowing some of the lye to precipitate out and crystalize. ..."

A room temperature 50% solution of NaOH and water will absorb water from the air until it's in equilibrium with the humidity in the air. You'd have to live in the driest part of the Mojave Desert to see a 50% NaOH solution lose water to the open air.

If you don't believe me, find out for yourself. Measure a few grams of dry NaOH into a lye safe container. Set the uncovered container in a safe place in the open air. Wait an hour. You'll most likely see a liquid in the container at this time, not dry granules. Find the weight of this liquid. Is it double the original weight of dry NaOH? Wait another hour and find the weight of the liquid now. Is it more than double the dry weight of NaOH? Repeat until the weight stabilizes. Calculate the lye concentration at this point and you'll know the concentration where the lye mixture won't absorb or lose water at a given relative humidity.​

The more likely reasons for the solid lump of NaOH -- the NaOH wasn't completely dissolved to begin with or the NaOH solution got too cold (unlikely in Florida, I'd guess!).

Another possibility to explain solids in an NaOH solution is sodium carbonate settling to the bottom. But sodium carbonate typically forms a powdery layer that can be easily mixed into the solution. In my experience, it never makes a hard large lump.

I had the experience before with crystals at the bottom of my master batch. It had been stored in the basement where it was cool, especially in the winter. Now, in the summer, the sodium hydroxide has stayed in solution in the bottle. Question: Is it possible to warm a bottle in a warm water bath of about 100°F, or in the summer to warm the MB lye in the sun, and then stir the master batch to get the sodium hydroxide crystals to dissolve? Or would that be dangerous?

 

[violets2217]

I had the experience before with crystals at the bottom of my master batch. It had been stored in the basement where it was cool, especially in the winter. Now, in the summer, the sodium hydroxide has stayed in solution in the bottle. Question: Is it possible to warm a bottle in a warm water bath of about 100°F, or in the summer to warm the MB lye in the sun, and then stir the master batch to get the sodium hydroxide crystals to dissolve? Or would that be dangerous?

So I added water to my leftover solution w/ the crystallized pieces, stirred it and poured it down my shower drain & repeated until the crystals were dissolved. And I’ve heard of Soapers that have warmed up lye solution in a warm water bath that has gotten to cool. So in theory it could work. But this is my first time master batching, so I’m not positive.

 

[AliOop]

"...Enough water evaporated off to leave less than 50% water, allowing some of the lye to precipitate out and crystalize. ..."

A room temperature 50% solution of NaOH and water will absorb water from the air until it's in equilibrium with the humidity in the air. You'd have to live in the driest part of the Mojave Desert to see a 50% NaOH solution lose water to the open air.

I agree that room temperature lye solution will absorb water from the atmosphere. However, I should have been more specific about my assumption she had left the hot, mixed solution uncovered, and thus lost some water to evaporation at that time - not later, when the solution was cooled. So the evaporation would occur while the solution was hot, and then the precipitation would occur after it was cooled (assuming it was covered by that time).

There have been frequent discussions on this forum by those who master-batch their lye solution, referring to this initial evaporation, and the need to weigh the solution after it has cooled, and then top off the evaporated water. Hopefully that clarifies what I was trying to say.

BTW, I personally don't leave my MB lye solution uncovered while cooling. I put the top on and leave the cap open just a crack. I generally don't lose anything to evaporation this way.

 

[The_Phoenix]

So I added water to my leftover solution w/ the crystallized pieces, stirred it and poured it down my shower drain & repeated until the crystals were dissolved. And I’ve heard of Soapers that have warmed up lye solution in a warm water bath that has gotten to cool. So in theory it could work. But this is my first time master batching, so I’m not positive.

I made a mb a few months ago in a hurry and not all of the lye dissolved because I did not properly stir it in. My fix was to add about 10 grams of water to the solution, and stir with my spatula. That "new" water heated up the solution and eventually the lye dissolved. It wasn't terribly scientifically accurate, but it did work.

 

[DeeAnna]

I...Is it possible to warm a bottle in a warm water bath of about 100°F, or in the summer to warm the MB lye in the sun, and then stir the master batch to get the sodium hydroxide crystals to dissolve?...

Technically that's an option, but it's going to be very slow because you're counting on the solubility of NaOH in the existing amount of water to do the job. Since you've made a mixture that is close to saturation or possibly fully saturated, the solid NaOH won't want to dissolve much if at all.

Leaving the solution in the sun isn't going to warm the mixture enough to alter the solubility enough to make a great difference -- you would want to add heat. I don't have time to hunt up the solubility tables to see what temps you would need, but they're readily available on the 'net if you care to look.

I have had good results from adding additional room-temperature water, breaking up any lumps of NaOH as best I can, and stir, stir, stir. If you plan to use the diluted NaOH solution, be sure to keep track of the weights of water you add so you can calculate the new NaOH solution concentration. Or you can back calculate the additional water needed to dilute the 50% solution to your usual NaOH solution concentration and only add that amount of water.

 

[violets2217]

I made another batch of soap for the column embeds because I wanted to try the ombré soap again. I made the embed batch with this MB lye before I realized it had crystallized. So, the embed looked the same when unmolding. But when I cut the bars of soap the embeds where all crumbly inside. So if my lye crystallized because I didn’t get it fully mixed, my water amount was higher than I assumed it was… so they are not lye heavy, right? I got no Zap, but I am still concerned. Maybe they got too hot? I put a wee bit more mica in the sun because I wanted it extra, maybe that’s where I went wrong! The column embeds are more complicated than I thought they’d be. And I so dislike silicone molds… my soap never turn out right when I use them.

 

[earlene]

I have heated lye solution that had a thin plate of crystalized lye on the bottom of the container by keeping it in a hot water bath. It took quite a long time to re-melt the crystalized plate, with almost constant stirring and reheating of the water bath (hot water in my kitchen sink.) At the time it seemed like a good idea, but I had no idea it was going to take so long.

I think DeeAnna's suggestion above would be a better option, which is what I will do if I ever have this happen again.