Slab mold ash

[JoyfulSudz]

After years of using only loaf molds, lately I've been experimenting with slab molds. I love the design options, but I'm getting a lot of soda ash on the surface. I spray with alcohol and cover the mold, but it hasn't helped. I'm using my usual recipe that rarely gets much ash. Is this a common issue with slab pours?

 

[Zany_in_CO]

After covering the mold, try insulating with old towels or a blanket for as long as it takes for the mold to feel cool, i.e., for the soap to go through full gel. Then cool down completely. I noticed @Zing mentioned that in a reply to a recent thread.

When using my 16-bar wooden slab mold, I don't always spritz with alcohol, but I do cover with 4-ply Mylar before putting the lid on. I then wrap it snugly in an acrylic lap blanket to insulate overnight. Usually, it's no longer warm to the touch by morning and ready to unmold... but not always. i leave it wrapped until it is.

I've never experienced soda ash. After Zing mentioned it, I'm beginning to wonder how many members insulate when they put their "babies" to bed?

Hmmm.

 

[JoyfulSudz]

After covering the mold, try insulating with old towels or a blanket for as long as it takes for the mold to feel cool, i.e., for the soap to go through full gel. Then cool down completely. I noticed @Zing mentioned that in a reply to a recent thread.

When using my 16-bar wooden slab mold, I don't always spritz with alcohol, but I do cover with 4-ply Mylar before putting the lid on. I then wrap it snugly in an acrylic lap blanket to insulate overnight. Usually, it's no longer warm to the touch by morning and ready to unmold... but not always. i leave it wrapped until it is.

I've never experienced soda ash. After Zing mentioned it, I'm beginning to wonder how many members insulate when they put their "babies" to bed?

Hmmm.

Thanks, @Zany_in_CO ! I did wrap the mold in a blanket, but being my usual impatient self, I uncovered it several times to peek. Next time I use the slab mold, I'll control my impatient urges until it's truly cooled and see if it helps.

 

[Zany_in_CO]

Next time I use the slab mold, I'll control my impatient urges until it's truly cooled and see if it helps.

I don't think "peeking" hurts all that much.
Just remember the First Rule of Soaping is PATIENCE.
i sure hope insulating makes a difference.
Please report back here, one way or the other.

 

[JoyfulSudz]

@Zany_in_CO Patience? Huh? What's that? Is there a book on that? A pill you can take to get some? Never heard of the stuff...

I'm off on a vacation in a couple days, so I won't have another chance to be impatient (at least not about soapy stuff) for a few weeks, but I'll let you know how the next attempt turns out. For now, I "fixed" the ashy soaps by giving them a brief bath.

 

[Catscankim]

Is that a dancing hippo in a tutu? LOL.

I never have good results getting rid of ash once it forms, except planing them. but sometimes that's not possible if you have a decorative top. I tried alcohol, steaming with an iron...

Probably my second best way to get rid of it besides planing it is washing it a little. Otherwise I "embrace the ash".

I haven't seen a difference between loaf mold and slab molds as far as having more ash on one or the other.

 

[Mobjack Bay]

I peak at my soaps all the time and very rarely get ash these days. I started using 40% lye concentration for most recipes about a year ago (or more?) and it has made a huge difference, especially when working with batter that is at emulsion or a very light trace. I always cover and almost always insulate molds, but never spray with alcohol. For batches made in slab molds, I usually also put the mold on a heating pad for a couple of hours. I’m usually starting a batch for a slab mold with the batter at emulsion and a recipe with coconut < 20%, batches < 1000 g of fats, and using non-accelerating scents. If I don’t help the soap stay warm for at least a couple of hours, a little ash will form at the edges and I sometimes also end up with slightly crumbly corners. If you don’t use a high lye concentration, you could try working at a little thicker trace, insulating a little more, or adding some heat to see if it makes a difference.

 

[JoyfulSudz]

Thanks for all these great suggestions.
@Catscankim Briefly washing the soap did help quite a bit, brought the bright colors back, but it does leave the soap with a bit of a used look. Still better than the ashy look.
@Mobjack Bay I intentionally kept the lye concentration at 35% instead of my usual 38% to help keep trace slow. I'll go back to my 38% next time.
For my first slab attempt I barely reached emulsion and it took the soap almost a week to harden. I was less cautious the next time, and it worked well except for all the ash. I did get some of those crumbly corners on that first one. Wasn't sure what caused them -- was it the too-little mixing?
BTW, that Workshop Heritage mold of yours is a beauty! Maybe one day... a girl can dream...

 

[The_Phoenix]

I regularly use my slab mold and get very minimal ash. If any at all. I honestly have no idea why I don’t get soda ash. When I do, it’s very faint. I spray the entire top of the mold with rubbing alcohol, let it fully evaporate, right before I take it out to cut. But like I said, it happens only rarely.

And I absolutely peek at my soaps. I put my mold in an insulated cooler and it gets HOT. Never need to add an additional heating element. After 24 hours when I take it out (or more like 18 hours because I get so darn excited to cut into it), it’s still quite warm. I use a 36% lye concentration. But that’s mainly because It makes it easier to unmold and cut sooner.

 

[Mobjack Bay]

@The_Phoenix I think I need to get a bigger cooler. The two I have are from food shipments. They work really well for loaf molds and my small slab molds, but are too small for my larger slab molds. I’m surprised by how much heat can build up inside a small cooler even when it’s only a 500 g batch.

@JoyfulSudz I just recently came across an article by Lovin’ Soap that shows a great photo of what can happen when an emulsion is weak. These days, I only ever have the issue at the bottom corners, which makes me think it’s due to a combination of a weakish emulsion and not quite enough heat at the distant edges. Maybe it would clear itself up if I left the soap in the mold for longer, but impatience usually wins.

I have used steam to clear up ash, and it helps, but the kind I get at the edges tends to be the kind that is more embedded in the soap rather than sitting on top.

One more thing! I have a working hypothesis that I can more easily get away with thinner emulsions if the FO tends to cause a tiny bit of acceleration when I bring a recipe to very light trace.

 

[JoyfulSudz]

@Mobjack Bay Great article, thank you!

I built these insulating boxes for my loaf molds. (Found the idea from a post on this forum but I don't remember who to credit for it.) They're not pretty, but they're super-insulating and also keep the molds from bowing out in the middle (especially useful for my T&S mold). If I finish my batch in the afternoon, it will still be a bit warm the next morning. I almost never have an ash problem in these. So maybe better insulation will do the trick for the slabs.

 

[Mobjack Bay]

@Mobjack Bay Great article, thank you!

I built these insulating boxes for my loaf molds. (Found the idea from a post on this forum but I don't remember who to credit for it.) They're not pretty, but they're super-insulating and also keep the molds from bowing out in the middle (especially useful for my T&S mold). If I finish my batch in the afternoon, it will still be a bit warm the next morning. I almost never have an ash problem in these. So maybe better insulation will do the trick for the slabs.

Oh, I remember thinking those insulating boxes are a great idea. I recently grabbed some thick foam core board from a discard pile at the office. The large sheet is broken in half, which is probably why they tossed it, but there should be enough to make a box for the 10” slab mold. It may not be as efficient as what you have, but it’s at least 1/2” thick.

 

[JoyfulSudz]

Oh, I remember thinking those insulating boxes are a great idea. I recently grabbed some thick foam core board from a discard pile at the office. The large sheet is broken in half, which is probably why they tossed it, but there should be enough to make a box for the 10” slab mold. It may not be as efficient as what you have, but it’s at least 1/2” thick.

Per the original instructions, I used Gorilla Glue to hold it together. It makes those ugly white oozes but is strong as can be.
Good score and good luck with your new boxes!

 

[melinda48]

After covering the mold, try insulating with old towels or a blanket for as long as it takes for the mold to feel cool, i.e., for the soap to go through full gel. Then cool down completely. I noticed @Zing mentioned that in a reply to a recent thread.

When using my 16-bar wooden slab mold, I don't always spritz with alcohol, but I do cover with 4-ply Mylar before putting the lid on. I then wrap it snugly in an acrylic lap blanket to insulate overnight. Usually, it's no longer warm to the touch by morning and ready to unmold... but not always. i leave it wrapped until it is.

I've never experienced soda ash. After Zing mentioned it, I'm beginning to wonder how many members insulate when they put their "babies" to bed?

Hmmm.

I use rolled insulation (it is an insulating blanket that has “foil” on the outside - like what is sometimes used to wrap hot water heaters). I spray my molds with alcohol, put my covers on and wrap them in the insulation. They gel beautifully without having to use the oven.

 

[melinda48]

After years of using only loaf molds, lately I've been experimenting with slab molds. I love the design options, but I'm getting a lot of soda ash on the surface. I spray with alcohol and cover the mold, but it hasn't helped. I'm using my usual recipe that rarely gets much ash. Is this a common issue with slab pours?

Wheat size slab mold are you using? My loaf molds make 3.23x3 soaps that I cut at 1”. I can’t seem to find a slab mold that would work for me. Thanks!

 

[JoyfulSudz]

Wheat size slab mold are you using? My loaf molds make 3.23x3 soaps that I cut at 1”. I can’t seem to find a slab mold that would work for me. Thanks!

The liner of the mold I have is 9.4 x 6.7 x 2.7 inches/ 24 x 17 x 6.8 cm. It makes soaps about the same size as yours. It's not the size I wanted, but I also couldn't find one that does. I would prefer bars the same size as my standard 10" loaf mold.