How Do You Warm RT Lye Solution?

[KristaY]

I'm toying with the idea of master-batching my lye but I don't soap at room temp. What's the easiest way to warm the lye solution? In the past I've had my lye cool more than I like so put it in a sink of hot water. If it's not too cool (less than 10* from where I want it) I warm the oils a bit more to compensate.

So to those who soap warmer than RT, what's the best way to warm the lye water? TIA!

 

[Arimara]

I don't see that as a safe practice so I wouldn't reheat lye. I'm content with warming my oils until at least melted.

 

[BrewerGeorge]

I'm sure people are going to freak out at this, but I'll be honest...

I've warmed it in the microwave.

Not that I'm recommending anybody else do that! At your own risk. YMMV. Etc.

 

[KristaY]

I'm sure people are going to freak out at this, but I'll be honest...

I've warmed it in the microwave.

Not that I'm recommending anybody else do that! At your own risk. YMMV. Etc.

Hahaha! I honestly gave that some thought but haven't had the nerve to try it.

 

[carlyjones]

I've created a double boiler before and warmed it that way.

 

[BrewerGeorge]

Hahaha! I honestly gave that some thought but haven't had the nerve to try it.

My reasoning is that I don't hesitate to heat a solution of sodium chloride and water, why hesitate to heat a solution of sodium hydroxide and water?

The difference, of course, is the consequence if something unusual happened - like a container breaking in the microwave. At least twice that I can remember, I've had glass or ceramic vessels break under microwave flux. But I don't use pyrex for lye any more, so that's not a problem. Boilover is another potential problem, but when I've done this I've never gone anywhere near boiling temps, and I've inched upward in temps with short pulses of the microwave.

Basically I've concluded that for me, with the safeguards I have listed, it's not appreciably more dangerous than handling the lye in the first place.

 

[IrishLass]

I master-batch my lye and I warm it up when needed by using a hot water bath. I just heat some water in a pot on the stove until a few bubbles form around the outer edges of my pot, then I pour it off into a suitably-sized container and set my lye solution container into it. Works great. I've been doing it this way ever since I started master-batching a few years ago.


IrishLass

 

[DeeAnna]

If I wanted my soap batter to be a little warmer than usual, I would warm my fats more to compensate for the cooler lye. Once you stir it up, the mixture is all going to be at the same temp anyway, so I can't see why it matters which ingredients get warmed in advance of mixing and which ones don't.

Also if you make a 50% NaOH solution and add water to dilute it to the % NaOH you want to soap with, the added water will cause the lye solution to warm up all on its own.

 

[BrewerGeorge]

If I wanted my soap batter to be a little warmer than usual, I would warm my fats more to compensate for the cooler lye. Once you stir it up, the mixture is all going to be at the same temp anyway, so I can't see why it matters which ingredients get warmed in advance of mixing and which ones don't.
...

But then you have to do enthalpy calculations to account for the lower heat capacity of the oils and the differing amounts. :twisted:

 

[HowieRoll]

I haven't master batched yet, so maybe I'm not fully comprehending the process (and math is not a strong suit!), but if you have to add more water to get the proper concentration of sodium hydroxide, could you heat the additional water prior to adding it to the masterbatched solution to raise the temp?

 

[mx5inpenn]

I master batch 50/50 so I just heat the balance of water needed for the recipe and don't worry about the lye.

 

[galaxyMLP]

I heat my oils more just like DeeAnna. I never hear my lye solution up more.

Alternatively, you can add a bit of water to your lye solution and it will heat right back up. Especially from a 50/50 solution. Mine usually goes from room temp to ~150 F or higher some times! In those cases I end up needing to wait for it to cool down again. The more water you add, the higher the temperature will go. Up to a certain point of course but it applies for the concentrations we soap with. This is with adding room temp water to it!

 

[DeeAnna]

I am sooooo not going there, BG. :mrgreen: But, yes, you're quite right. Reminds me of the miserable time I had in my sophomore class on energy and material balances with a visiting Hungarian professor. The Soup Nazi had nothing on him. :think:

But then you have to do enthalpy calculations to account for the lower heat capacity of the oils and the differing amounts. :twisted:

Yes, you could, Howie. But as a few of us have pointed out, you don't actually have to heat the water. Simply adding room temperature water to concentrated NaOH solution causes the solution to heat up. The reason is that a 50% NaOH solution is not fully ionized (broken up) into Na and OH as much as it would prefer to be. When you add water to make the lye solution more dilute, the NaOH is better able to ionize further and react with the water. The "joy" that NaOH "feels" as this happens causes energy to be released. That energy goes into heating the lye solution. :mrgreen: Brewer George and my Hungarian prof (and I) would call that the "heat or enthalpy of solution."

...if you have to add more water to get the proper concentration of sodium hydroxide, could you heat the additional water prior to adding it to the masterbatched solution to raise the temp?

 

[TeresaT]

But then you have to do enthalpy calculations to account for the lower heat capacity of the oils and the differing amounts. :twisted:

I suck at thermodynamics more than math. Just in case anyone cared. :-?

 

[doriettefarm]

I suck at thermodynamics more than math. Just in case anyone cared. :-?

You crack me up T! I'm married to a mechanical engineer who could probably school us all on thermodynamics but doesn't know squat about chemistry or soap making

 

[HowieRoll]

Yes, you could, Howie. But as a few of us have pointed out, you don't actually have to heat the water. Simply adding room temperature water to concentrated NaOH solution causes the solution to heat up. The reason is that a 50% NaOH solution is not fully ionized (broken up) into Na and OH as much as it would prefer to be. When you add water to make the lye solution more dilute, the NaOH is better able to ionize further and react with the water. The "joy" that NaOH "feels" as this happens causes energy to be released. That energy goes into heating the lye solution. :mrgreen: Brewer George and my Hungarian prof (and I) would call that the "heat or enthalpy of solution."

Thanks for the detailed (and easy to follow!) explanation!

If I ever get to the point of masterbatching, when adding the additional water I'll think of it as the lye solution is blushing, and whispering, awwwww, you shouldn't have...

 

[KristaY]

Thank you DeeAnna and Galaxy for the excellent chemistry lesson! For some reason I thought the NaOH and water did all they need to do when mixed the first time, irregardless of the solution strength (as long as it's 50/50 minimum). Now I won't have to give any more thought to RT lye causing me grief. I'll just add the extra liquid I need and let it do it's thing!