Soap Molds, Reposted

This is an old post–from April 2013, but still relevant! I still use 2 different sized soap molds (and sometimes more!), but even though the bars are shaped differently, they are well over 4 oz, making them a really generous size for your shower. 

I was reminded of this a few days ago when someone asked why some of my bars are smaller. They’re not! Just a different shape. The slab mold with dividers is an easy way of making salt and brine soaps that set up quickly, and can crumble if they aren’t cut in a timely fashion.

I was making 10 lb batches 2 years ago–now I make 50 lb or 100! But I still use the slab molds for salt and brine soaps. They’re a specialty item that really can’t be done in large blocks. 


As my business has increased, I’ve looked at different ways to increase the batch size of my soaps. My old 2 lb silicone loaf mold? Now it’s only for test batches. Even the 4 lb upright mold that I love is really too small.

I’m regularly making 10 lb batches, often more than once a day, along with the balms and other items.

My choice now is between “log” or “loaf” style molds–essentially, a 5 or 10 lb loaf of soap that I then cut–or a “slab” style, with or without inserts (pictures below).

The 36 bar slab mold with inserts from Bramble Berry

Each has advantages: The log molds are a standard size, and with the multi-bar cutter, the bars are identical or nearly so in size. The silicone liners for the 5 lb mold mean no finicky lining with freezer paper, something I’m terrible at.  If you like to gel your soap (and usually I do), there is enough mass to generate and hold the heat. The only downside is that some swirling techniques can’t be done, or done easily, in a loaf-type mold.

5 pound log style molds with silicone inserts

I’ve been using 5 lb molds from Bramble Berry, with silicone inserts. The problem? The inserts are just a shade too big for the molds–apparently, there was some retooling, and they fit better with the slide bottom molds. So I’ll be trying the slide bottom molds in a few weeks. [Update: Bramble Berry replaced the wooden molds with the slide bottom molds, pictured above, and the silicone inserts now fit fine.]

In the meantime, though, I’m giving my 10 lb slab mold, with inserts, a work out. The mold is just what it sounds like–a 10 lb slab, with plastic inserts. The mold is lined before the inserts go in, but because the lining is covered by the smooth plastic sides and bottom, I don’t have to be as precise and wrinkle free. The mold also includes dividers. Pour in your soap batter, insert dividers, let it harden, and turn out 36 bars of soap, about 4.5 oz each, that are, theoretically, perfect. The slab shape allows you to layer, swirl, do column pours, and all the rest. Here is a simple slab of After The Garden soap, a goat milk and cocoa butter formula with shredded loofah. The slab is about 12 hours into gelling at this point. I have a seedling mat underneath to give it just a bit of warmth, and there is a tight-fitting lid to keep the heat in.

After the Garden

There are a few caveats when using this mold. If the recipe is for a softer soap, the soap needs to sit in the mold, with the dividers, for a few days before removing. Or use salt in the lye water, or add beeswax, or sodium lactate. The goal is to get the soap hard enough so that it doesn’t tear when you remove the side panels and inserts.

My method of removing is to tip out the whole 10 lb slab–bottom, sides, and all, then ease off the side panels, and pry out the inserts gently. In this photo, I messed up the inserts–they’re upside down, and the flat part visible in the picture should have been down. But in the end, it didn’t matter much.

The results soaps are relatively uniform in size–assuming you spread your soap batter evenly before putting in the inserts. And with enough time or salt or beeswax, the bars slide and twirl off the plastic without ripping.

One thing to notice is the bar size: while the resulting soap is about 4.5 ounces, just like the bars from the loaf-style molds, this bar is narrower and thicker–about 2x3x2. My usual bars are more like 2×3.5×1.

In this picture, compare two lavender soaps. Same recipe, close to the same weight (both well over 4 oz, my label size), but the shape is very different.

The bar from the slab mold might look smaller to some customers, though it is twice the thickness of the bar from the loaf mold. I like the feel of the bar from the slab mod–it fits better in my hand, and “twirls” in a washcloth better. But ultimately, it’s my customers who will decide.

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