Thursday, January 16, 2014

Soap Crackling

*Please see Edit at the end of this post.
Crackling or Glycerin Rivers isn't an issue that I generally struggle with.  I believe that it is occurs when soap that contains Titanium Dioxide overheats.  Since I primarily soap in an HDPE mold at cool temps, this almost never happens. 
 
 
 This is my most recent batch of Achilles Bay.  It's a fresh and tropical aquatic blend.  See those clear veins?  That's crackling.  It doesn't affect the soaps performance in any way.  Cosmetically, it's just a bit of a nuisance.
 
 
Since I've been using my temporary wooden mold, almost every batch has a bit of it.  None like this one though.  So, I'm guessing that the  fragrance blend may have a role to play in this as well.
 
 
Here's a batch of Beguile made the same day in the same mold.  This is a coffee and marshmallow blend.  All of these soaps heated so much that most of them cracked on top.  Again, something I don't normally struggle with.  The wood must really hold heat!  If you look very closely, you may see that the swirls inside the bars have a bit of crackling.  The white portion on top of the bars doesn't have any though.  Go figure.
 

I thought maybe it had to do with my switching to water soluble TD.  But in this batch of Sundance, there's no crackling.  All citrus notes here with just a bit of clove.
 
 
Same with Geisha.  I used TD for the white base.  This has sweet florals and plum.  I'm not sure if it went through full gel but it did heat up so much that you could smell the scent around the corner, up the stairs and into the kitchen.  Yet the loaf was crackle free. 
I'm just really a confused soaper right now.  Any thoughts?  I'd love to hear them.

*EDIT:  I just wanted to highlight this response by Andee from The Sage.  I found it very helpful and wanted to make sure my fellow soapers benefit from it as well.
My experience is that Titanium Dioxide (and clays) show this off, but the "crackle" is actually is an underlying occurrence in a soap due to multiple possibilities. Titanium Dioxide doesn't cause the crackle, it just acts as a magnifying glass or microscope.

Crackle is (in my experience) caused by fatty acids in the oils that had not melted completely or started to solidify again. This is more common in soaps that have lower starting temperatures, techniques that are cool or use lye to melt the hard oils, or even oils that weren't melted completely. Excess heat hasn't been a culprit for me, but using oils that have a fractionation problem (or are prone to fractionation) as well as oils that have a high amount of unsaponifiable matter like lanolin or jojoba can also contribute to crackle.

This happens in more batches than we realize because only Titanium Dioxide and clays highlight this. When we have a dark soap colored with cocoa, pigments or micas, it won't show up as easily because they are different from Titanium Dioxide and clays (which behave similarly in soap).

I don't know the complete scientific reasoning behind this, but this is what I've had experience with and asked questions of the Technical Team here at TheSage.
 
 

5 comments:

  1. All your soaps look great, even the one with the crackle. I know what you mean though about the crackle being a nuisance. I live in a hot and humid place, use both wooden and hdpe molds, and insulate with a towel (I like getting a full gel). Out of more than a hundred batches, I've experienced getting the full crackled effect only once, very recently. I can't figure out either why it happened. In fact, I accidentally put too much water in that batch, which I think should have made it less susceptible to overheating. There were no surface cracks, just crackles. I also hope someone can enlighten us about this crackling phenomenon. :-)

    ReplyDelete
  2. My experience is that Titanium Dioxide (and clays) show this off, but the "crackle" is actually is an underlying occurrence in a soap due to multiple possibilities. Titanium Dioxide doesn't cause the crackle, it just acts as a magnifying glass or microscope.

    Crackle is (in my experience) caused by fatty acids in the oils that had not melted completely or started to solidify again. This is more common in soaps that have lower starting temperatures, techniques that are cool or use lye to melt the hard oils, or even oils that weren't melted completely. Excess heat hasn't been a culprit for me, but using oils that have a fractionation problem (or are prone to fractionation) as well as oils that have a high amount of unsaponifiable matter like lanolin or jojoba can also contribute to crackle.

    This happens in more batches than we realize because only Titanium Dioxide and clays highlight this. When we have a dark soap colored with cocoa, pigments or micas, it won't show up as easily because they are different from Titanium Dioxide and clays (which behave similarly in soap).

    I don't know the complete scientific reasoning behind this, but this is what I've had experience with and asked questions of the Technical Team here at TheSage.

    P.S. Your soaps are lovely! The coffee & marshmallow looks good enough to eat!

    ReplyDelete
    Replies
    1. Thanks you so much for taking the time to address this Andee! That is the most comprehensive explanation I've seen on this too date and I'm sure it'll will prove very helpful to my readers as well :0)

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