Problem when cutting soap

[featherbrained]

I made a very pretty 4# loaf of espresso layer CP soap. I took it out of the mold after about 36 hours and cut it. I used a wavy cutter and a guide box, but the cuts came out "u" shaped and bowed in the middle. The guide is straight and the cutter is not bent or curved, so I'm not sure what happened. I had just cut another loaf of soap without issue. Was my soap too hard and made the cutter bow, or what could have caused this?

I've also had trouble with cutting apart soaps from a plastic mold. The edges crumbled off the bottoms. It was a mold I had for a long time but had never used. Did I leave it in too long (I think I left it in about a week), or was it a problem with the soap itself? It also stuck a bit in the mold, and I thought it was because I hadn't left it in long enough (most of the stuck ones were in the middle of the 5# mold).

 

[claryza]

I usually cut my soap after 24 hours so they are still soft to be cut. Unless you use a lot of soft oils or ungel them. The longer you cut the harder the soap you have to cut. Is the plastic mold individual molds or loaf?

 

[featherbrained]

It's individual soaps http://hoeggerfarmyard.com/xcart/Large-Tray-Kid-and-Butterfly-Soap-Mold.html

 

[hozhed]

Wood does this same thing when it dries. One side drying out faster than the other makes it bow...........

 

[Susie]

I cut my gelled soaps at about 18 hours, and ungelled at about 24 hours. I push on one corner of the soap in the mold to see how squishy it is, as soon as I can apply light pressure without leaving a mark, it gets cut.

 

[DeeAnna]

Regarding the bowed soap -- I suspect it's the result of operator error.

If the cut soap came out of the cutter with that kind of bow, then you are putting enough pressure on that wavy cutter to bow it while it is making the cut. When you look at the cutter in the open air, it will look fine because the metal is springy. It's actually pretty easy to do that, especially with a wavy cutter, although I'll say that I think I would notice that much of a bow if I was cutting the soap like that. If you're getting a bow while cutting, pay strict attention to how you are doing the cutting and perhaps you will discover why the problem is happening.

If the cut soap comes out of the cutter straight, but bows later, then something is causing the bar of soap to curve. If one flat face of the soap is flat against a solid material that prevents evaporation and the other side is in the open, I suppose this could happen. If you're laying the soap flat on a surface, then lay the soap properly on its side to dry (as in your picture). See if that helps.

"...The edges crumbled off the bottoms...."

I'd say you waited far too long to cut. When soap gets brittle, you will see this kind of crumbling -- the last bit of the uncut soap breaks apart as the blade nears the end of the cut. Every soap is different, so you will need to test as Susie describes rather than just wait a specific amount of time.

 

[featherbrained]

So would I cut using less pressure? I'm just pressing straight down on it like I cut

my other loaf, nothing different. It definitely happened while cutting.

I will try taking my soap out of the plastic mold sooner and cutting it, to see if that helps.

I did use sodium lactate in the lye water, and I noticed the soap got kind of foamy when I was stick blending it, which has never happened with my other soaps. I am also wondering if there are bubbles in the soap itself.

Going to try again on the mold and see if I can take it out sooner and cut it better. I also used a kitchen knife, and maybe I will try with some fishing line or a wire instead and see if that helps.

 

[featherbrained]

Wood does this same thing when it dries. One side drying out faster than the other makes it bow...........

It happened when cutting, not when drying. I cut it yesterday and it is drying now. I guess I will have some interesting shaped bars. On the bright side, it will keep most of it out of the moisture when it's used, so maybe it will not melt as fast as a flat bar.

 

[DeeAnna]

I suppose there could be bubbles in the soap, but I wouldn't think they would cause that much of a bow. I sure hope you can figure it out!

 

[featherbrained]

I suppose there could be bubbles in the soap, but I wouldn't think they would cause that much of a bow. I sure hope you can figure it out!

Sorry, I didn't mean for the bow. I shouldn't be talking about two different soaps and two different problems at the same time. I mean for the goat soaps in the plastic mold, that crumbled on the edges when I cut them.

 

[DeeAnna]

Oops -- I sure missed your point there! Thanks for correcting me....

 

[AmyK]

"...The edges crumbled off the bottoms...."

I'd say you waited far too long to cut. When soap gets brittle, you will see this kind of crumbling -- the last bit of the uncut soap breaks apart as the blade nears the end of the cut. Every soap is different, so you will need to test as Susie describes rather than just wait a specific amount of time.[/QUOTE]


This was super helpful, I have been having the bottom edges crumble and I was not sure what the problem was, I have tried every knife I own and was still having the same problem.

 

[featherbrained]

I made another batch for the goat kid & butterfly mold, and took it out after approximately 12 hours. It stuck really bad, and when I cut it, it did the same thing, though not quite as bad. I used a straight bladed cutter (like a bench knife) this time. I can see this is going to be a challenge to figure out the correct amount of time to leave the soap in the molds.

I did spray the mold with cyclomethicone before I poured the soap. I did not use sodium lactate in this batch, which I did do with the first batch.

If I do a rebatch of this soap, will it be possible to use the mold again, or is a detailed mold impossible to use with a rebatch? I'm thinking I should just use a regular wooden mold for the second go-round on this one.