Lye/Soap and cold weather

[Buckscent]

Has this ever happened to any of you all?

So yesterday it started getting cold here (AL) so I was going to make a batch of soap when I got home from work. As normal I go to the shop and it is cold in there (low 40ish) no heat (yet). I mix up as normal my lye/water and oils and let them sit for awhile, I like to mix and room temp so 80/90 or so. I go back to the shop and the oils looked jelled, like they are hardening again, no big deal I will warm them back up. But when I looked at the lye/water it had a hard bottom, like it froze. Not all of it but about 1/8 inch of the bottom was hard.... I was making GM soap so I used 9.2 oz of water to 9.08 oz of lye. Why would it harder on the bottom like that? water/lye ratio? cold? temp was like 70

 

[dixiedragon]

That's happened to me. That's why I don't use ice in my lye water - I used to measure out a portion of my water in ice so the lye solution would cool faster. That's also why I use canned milk for soap - whenever I try the frozen milk method, I get un-dissolved lye. My best tip is to stir the lye water vigorously - that's why I like to use a pitcher vs something shallow. Tip the pitcher around a bit to make sure there is no lye settling on the bottom.

 

[snappyllama]

When you mixed your lye, did you keep stirring it until it was completely dissolved?

 

[Buckscent]

I didn't use any ice or frozen milk. I mixed my lye and water as usual. Recipe calls for 18.2 oz of water and 9.06 oz of lye. I used half of my water to mix with my lye. 9.2 oz of water and all of the lye 9.06. I added the other half 9.2 oz as milk to my oils.

 

[dixiedragon]

I think the cold water slows the reaction and gives the lye a chance to sink to the bottom vs dissolving. Also if the pitcher has a domed bottom the lye can sink into that ring and then miss being stirred. I usually pour the lye water into another container, use a butter knife to chip out the lye ring and break it into bits, and add a bit more water to dissolve it.

 

[BrewerGeorge]

How cold are we talking? You're already quite close to max solubility for lye, and solubility goes down with temperature. So even if the lye was already fully dissolved, it's possible for it to come out of solution if it gets cold enough. Though I would think that would produce more of a fluffy condensate instead of a hard one.

 

[Buckscent]

How cold are we talking? You're already quite close to max solubility for lye, and solubility goes down with temperature. So even if the lye was already fully dissolved, it's possible for it to come out of solution if it gets cold enough. Though I would think that would produce more of a fluffy condensate instead of a hard one.

(low 40ish)

 

[BrewerGeorge]

(low 40ish)

So maybe 5C then...

That knocks the solubility down to around 33% (50g lye in 100g water).

It probably precipitated out of solution.