Cracking & round molds

[Hales]

I have read that cracking tends to be a result of too high heating once in the mold. And it tends to be higher in wooden molds. Well, I primarily use a wood log mold and haven't had any cracking. I just started using a circle PVC mold. As I went to unmold it, I noticed cracking throughout the center. I can't imagine that it got hotter than my wooden molds. Any other reason might this might have happened?

It was a olive oil, palm oil, coconut oil base with grapeseed oil and vanilla fragrance added.

Thanks!

 

[carebear]

oh the PVC pipe/cylinder molds get hotter than anything else! hot hot hot! I don't insulate them at all and I still always get some overheating.

 

[mandolyn]

oh the PVC pipe/cylinder molds get hotter than anything else! hot hot hot! I don't insulate them at all and I still always get some overheating.

My PVC soaps don't crack. Well, 2 did, but I was watching them carefully & when I saw the top bulging, I just pushed it down, then sat the mold over the air conditioning register. I was still soaping with warm oils.

Now that I've started soaping with my oils at room temp & my lye/water anywhere between 85 & 110 F, I never get overheating in my PVC. I do get full gel.

For me, lower soaping temps resolved the overheating issue.

 

[welder]

As a student of biofuels, I know that when comparing technical notes on cases of different personal results, it is important to consider that the different results can not only be produced by different chemical recipes and different hardware materials (PVC in this case), but also can be due to different climatic conditions.

For example, Hales may live in a warmer area like Texas or Nevada, while Mandolyn may live in Denver or Chicago.

What I'm saying is the even if the soap recipes were identical & the hardware (PVC molds) were identical, a large variance on ambient temperature could easilly account for the different results.

Just a though, that's all...

 

[KnitchyFingers]

I think it has something to do with less surface area of the soap being available for heat release in a round mold, thus, overheating in round molds happens more often.

In a wooden mold, more surface area (presumably one whole side of the log or slab) is exposed for heat release, thus, less likely to "heave" (the name for that darn crack). In a round mold, the only part of the soap exposed for heat loss is the very end, thus, the soap is more likely to overheat and heave.

I've heard of lots of people putting their round/PVC molds in the fridge right away after pouring.

Hope that makes sense!

 

[carebear]

I think it has something to do with less surface area of the soap being available for heat release in a round mold, thus, overheating in round molds happens more often.
...

Hope that makes sense!

agreed, as I tend to get overheating in my pringles cans too - and those are hardly insulating.

 

[Hales]

Thanks!

After cutting it, the crack was only about an inch deep. I am going to try another batch tomorrow and not insulate it at all.

 

[Jaaret]

I think it has something to do with less surface area of the soap being available for heat release in a round mold, thus, overheating in round molds happens more often.

I also agree. I use cardboard tubes as molds and have found they often heat up a LOT with fresh soap in them. I'm sure one of the factors is there is less surface area for heat to escape. I'm learning to compensate by making soap at lower temperatures, being careful how much beeswax I add, and keeping the cardboard tubes in the freezer until just before I pour the soap into them.