What Causes Unwanted Marble Effect

[Ravenscourt Apothecary]

I've noticed that some of my batches come out with this strange marble effect when I cut it (everything is smooth on the outside, you'd never guess by looking at the uncut batch). I'm attaching a picture to make it easier to see what I mean.
Most of my batches don't behave like that - the color is uniform throughout, with no unwanted swirls or 'marbliness'. I'm not sure what causes it. These three are colored with all different things, the top one with tea, the middle one with clay, and the bottom one with purple oxide. Any idea what might be causing it?

 

[tinytreats]

I don't really know what this is caused from, but this just happened to me as well 2 weeks ago. If I had to guess, I would say it's from not blending well enough? What do you mix your colorants with? Because my marbling effect was with water soluble Titanium dioxide. So I assume I didn't blend my TD well enough.

 

[Ravenscourt Apothecary]

tinytreats,
I stick-blended it, the same way I do with every other colorant I use, in approximately the same proportions to the soap mass. I'm really scratching my head as to what it could possibly be. When pouring the soap into the molds, it was all homogeneous-looking, with nothing to suggest that the marbliness could happen.
Also -the very top soap was colored ONLY with tea (in place of lye water), so everything in the batch was being blended together from the very beginning, with no other additives to the mixture in the process, so I REALLY don't see how it could be from not mixing everything properly.
I sympathize and hope someone can tell us what the heck it is.

 

[Arthur Dent]

The bottom two look like the swirling in a soap I made a couple of weeks ago. Being new at this I assumed it was normal.

 

[Ravenscourt Apothecary]

Arthur Dent
It'd be one thing if I was AIMING for the swirls, using two colors, etc etc. But I didn't! I do one solid color batches, and I'm trying to eliminate the factors contributing to the swirls/marbliness out of nowhere.

 

[dixiedragon]

Somebody said that that comes from over heating and some of the glycerin separates out a bit.

 

[judymoody]

It has to do with how hot your soap is when it gels, the rate at which it cools down, and (probably) the stearic acid content of your soaping oils (higher the stearic, more likely to get streaks). You could try soaping cooler or avoiding gel if you want to try to prevent it. Using Titanium Dioxide can make the streaks more visible.

 

[Ravenscourt Apothecary]

dixiedragon, judymoody
Thank you, that makes sense. The stearic acid content in all my soaps varies from 3 up to 17; the streaks happened in soaps with stearic content being 5, 13, and 17 (so basically covering the whole range). I think it has more to do with the temperature and the separation of glycerin - I'll try soaping cooler, but I do like to ensure full gel with CPOP, so I'll just start with a cooler temperature oil mix, and see if it helps.

 

[Lin]

I have a soap that marbled like that and it did not gel, it was stuck in the freezer. I colored with cocoa powder and there are lighter colored marbles throughout identical to the pictures here. Initially I thought some spots were maybe dryer and it would go away with cure but it didn't.

 

[Ravenscourt Apothecary]

Lin,
So you're saying that a soap that marbled did not go through the gel stage at all... That sort of ruins the previous theory (due to overheating/glycerin separation). Was your soap high on the stearic acid?

 

[TVivian]

My theory about this is that the soap batter forms a "skin" almost immediately. A super thin layer on top that happens as soon as you stop mixing (especially if the trace is thinner) and as you slowly pour the batter into the mold the top layer is forming the "skin" which is then making a pouring pattern in the soap. So when I make a solid color soap with no embeds or swirls. As soon as the soap is poured into the mold, I take a wire whisk and sink it into the batter and slowly bounce it around the mold *slowly so no bubbles form* this method has also helped me get rid of little bubbles.

 

[shunt2011]

I agree with too hot gelling. I have this happen if my soap gels too hot. I have since stopped adding extra insulation and just put the lid on and let it go. I do RTCP and sometimes it takes my soaps a couple hours to start the gel phase.

 

[Lin]

No, wasn't high on stearic at all. I'll see if I can get a photo of it but I only have my cell phone to take pictures (plus worlds shakiest hands it always seems!) so I'm not sure if it will show well. The stearic is an 8 from soapcalc on my recipe.

I first thought the spots were dryer, especially since I had an issue with slight color differences and dryer soap spots in a batch of soap I made colored with celery herb for embeds. But I cut out gingerbread men and the swirls were on the inside too not just outside so that didn't seem right. But I still thought maybe they would go away with cure.

Then I thought maybe I hadn't blended the cocoa powder in for color well enough, but man I was blending that with the stick blender for what felt like ages, actually even went too long and my soap thickened up to a medium trace before I poured. I was just worried about the powder incorporating well enough that I kept going and going, so of course my paranoia wondered if that was the problem when it didn't go away with cure but in reality I highly doubt it. Especially since I've used it again and other colorants since and been fine with blending less.

 

[tinytreats]

Thought that I should add that I soap at room temp and pop my mould into the freezer for 24 hours, then into the fridge for another 48 hours. So I don't think it's overheating. And my soap recipe is not high in stearic acid.

We need more theories!