Soap with crumbly and cracked edges

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I made a batch of soap with Dragon’s Blood that I bought from @cmzaha and although I love the smell and how the soap feels on my skin, the edges are rough, crumbly and cracked. Would you please give me advice on how to tweak this recipe so that the edges will be smooth next time I use a similar formula? I am attaching the recipe and a couple of photos here and I hope you can see them. Many thanks in advance for your help!

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By the way, after I poured the soap batter in a mold, I wrapped it in a blanket, unmolded it after 18 hours or so and cut it immediately using a tool pictured in the photo below.

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Your soap looks good! I don't see the cracking or crumbling you were talking about.

Are you married to the idea of cocoa butter in your soap? It might be causing some brittleness. Also, that's a high percentage of coconut, which makes a hard bar quickly (vs olive which will make a hard bar slooooowly.)

What type of olive? Pomace behaves very differently than other types.

I would tentatively suggest:

Castor 5%
Coconut 20%
Cocoa butter 10%
Olive 65% OR divide between sunflower, olive and ricebran
 
With that much water in your recipe (just over 27% lye concentration, which is a lot of water for a predominently olive soap), it would have gone into gel fairly easily. Coconut tends to gel fairly hot, so the combination would mean that your soap was probably ready to cut many hours before you actually cut it.

Without making any suggestions on the recipe itself, I would suggest to you that you use a water amount that is somewhere between a 30% to 33% lye concentration (and move away from lye as a percentage of oils - this leads to fairly unpredictable water values and a water amount that is too high for olive based soaps) for future recipes.

For cutting, when the soap is no longer easy to dint if you push on it with your finger, then it is ready to cut. High coconut soaps tend to need cutting when they are warm, they harden up so much and will crumble when they are cold (not sure whether the percentage you used would cause this effect, but it's worth knowing this can occur with coconut soaps).

Cocoa butter does cause brittleness, but I like it in soaps (and have used it at the concentration you have) ... just cut before the soap is too hard and you will be ok.

Crumbling can also occur when you cut too early (when the soap is still fairly soft). This is more often a problem with ungelled soaps, but for gelled soaps, using the finger test (until you get used the timing and look of your recipes) to test the hardness of the soap will help you increase your understanding of what texture/hardness is best to cut at.

Ultimately, the thickness of the blade has pushed the bottom edge of the soap away from the surface because it's easier for the soap to crack and break than for the soap to move away from the blade as you slice through (it's not much of an effect - this would happen more with a wedge shaped knife). If you cut when the soap is at the "right" texture - not too soft, not too hard, the crumble won't happen with that blade. A wire has even less of this effect (there is even less soap being pushed around when cutting with a wire).

It is not terribly noticeable on your soap. If it concerns you, you can tidy it by bevelling the edges with a peeler (or similar) :)
 
Everyone so far has good suggestions, and I don't have anything to contribute about your method or your recipe. But I do have another suggestion for you to consider --

I see the U-shaped wood holder for your soap cutter has a shallow cut (kerf) right where the blade touches the wood after it passes through the soap. You have to provide a kerf like this for a wire cutter to work properly, but this kerf is unnecessary with your dough cutter blade.

I suspect the chips on the edges of your bars are caused by that tiny bit of open space under the soap. That last 1/8" of the soap has to be fully supported as the blade comes or the chance of chipping is pretty high.

Try putting a piece of firm cardboard on the bottom of the holder so that kerf is covered up and see if that helps. If it does, perhaps you can find something more durable to permanently fill or cover up the kerf. I think if you do, your dough cutter blade will work much better.

IMO, the chipping is not a huge issue -- just a little bit unsightly -- but if you're like me, you pay attention to details and want your soap to look as nice as possible!
 
@dixiedragon, @cmzaha, @SaltedFig, @DeeAnna, thank you all so very much for all the helpful tips and advice! Wow, you are so kind and helpful!

The olive oil I used was not pomace. It's just regular olive oil I got at Trader Joe's.

This was the first time I used cocoa butter in my soap and I am not sure yet if I like it.

Next time, I will increase the amount of olive oil, decrease the amount of cocoa butter and coconut oil, use a 33% lye concentration, move away from lye as a percentage of oils, try cutting the soap when it's not too soft but not too hard by testing it with a finger press (possibly when it's still warm), and put a piece of firm cardboard on the bottom of the holder of the cutting tool when I cut the soap.

This is really helpful and so very appreciated! I learned a new word, "kerf," thanks to DeeAnna, too :)

If I use shea butter instead of cocoa butter, does that make the soap brittle, too? Do they behave similarly in soap?
 
IMO shea butter behaves a bit better in soap than cocoa butter.

The texture you want is for your soap to be like a block of cheddar cheese. Cream cheese - too soft and sticky you'll end up with mushed bars. Parmesan - too hard and brittle. (I like cheese. :) )

Another tip - try wetting your blade between cuts. That will help the blade slide and not stick.

Try using a vegetable peeler to bevel the rough corners off of your soap, if it bugs you.
 
@dixiedragon, thank you very much for the cheese analogy! I love cheese, too so that's easy to remember :)

I will try wetting the blade between cuts, too next time.

Yes, I did use a vegetable peeler to bevel the edges. It worked pretty well :) Thanks!
 
Another tip -- if your soap is too brittle and hard to cut nicely, you can try warming it in a 145-170 F (62-70 C) oven for 1/2 to 1 hour. Then try cutting the warmed soap. No promises of 100% success, but it's worth a try.

I would say in the case of the soap shown in your first post, it isn't so hard that you would need to warm it. Just give it a little more support on the bottom -- that will hopefully work fine.
 
Another tip -- if your soap is too brittle and hard to cut nicely, you can try warming it in a 145-170 F (62-70 C) oven for 1/2 to 1 hour. Then try cutting the warmed soap. No promises of 100% success, but it's worth a try.

I didn't know that you can put the soap in the oven to warm it up again! Very good to keep in mind. Thank you, DeeAnna!
 
Hi! I incorporated your advice into making a new batch of soap using shea butter and tallow instead of cocoa butter and the percentage of each oil slightly modified. I used 33% lye concentration instead of water as % of oils. I used the cheese analogy and unmolded and cut the soap after 12 hours or so instead of waiting for a full day.

I did put down a piece of thin cutting board that I cut out to fit the bottom of the cutting tool and wet the blade between cuts.

I didn't need to warm up the soap in the oven:)

hanks to everybody who gave me great advice here, the sopa is looking good and has no crumbly or chipped edges!

Thank you so much, everybody!!

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