Choosing the right soap molds for cold-process recipes
Tips on types of materials and containers that you can use as soap molds. Includes materials you should avoid and ideas for wooden, silicone, recycled, and custom soap molds.
In most of my soap recipes I show the type of soap mold I use and/or recommend. In many of my more recent ones it’s often the pink six-bar mold you see below. It’s convenient, easy to use, lasts a long time, and fits a 1-lb soap recipe perfectly. There’s a WORLD of soap molds out there though, both that can be purchased and can be made. You don’t have to feel constrained by what you see in my recipes though. Choosing the right soap molds is one way that you can personalize soap recipes.
In this piece I’ll take you through common mold types, explain their pros and cons, and give ideas for where to can purchase them online. In some cases the molds will already be in your own home and in that case we’ll look at how they can be prepped to use in soap making.
Silicone soap molds
I have an entire collection of silicone soap molds. Heart shaped, flower shaped, basic rectangles, loaf molds, the list goes on. You name it and I probably have it. Silicone is my go-to for small to medium batches because they’re so diverse and very easy to release the finished bars from. A tug from the side and a push from the bottom is generally all you need to do to get them out.
Silicone is non-toxic, lasts for years, and doesn’t need lining or prepping. You pour your cold-process soap in and pop them out when it’s time. One of my favourite silicone molds is a loaf style mold that I can fit an 800g (28.2oz) batch in perfectly. I’m also a big fan of this rose shaped mold that I used in a recent Valentine’s Day soap recipe.
Gelling in Silicone Molds
Silicone molds come in loaf style and small cavities. The latter can come as individual molds or a one piece set of small cavities. With loaves you’ll need to pay close attention to soap making temperatures since the centers tend to gel and the outside doesn’t. This can leave darker rings inside the soap that you’ll only see when cutting the loaf into bars. If you don’t want your soap to gel at all, make it at a lower temperature and/or refrigerate after you pour it.
One downside that you’ll hear about small cavity silicone molds is that soap has trouble gelling in them. I have a trick for that. Silicone is heat-resistant and can be oven processed. After pouring your soap in the mold, pop it in an oven warmed to about 110°F, but turned off, and leave overnight. The color will be gelled and your soap won’t have soda ash. This applies to both loaf and cavity silicone molds.
Here are some of my picks for silicone soap molds you can buy online:
Cooking & Soap Making Equipment
A lot of folks will already have silicone molds in their kitchen cupboards. Not only are they easy to make soap in but they’re a breeze to pop cupcakes and muffins out of too. Which begs the question: is it okay to use silicone molds that will be used for baking too?
For a long time I’ve held to the thought that soap making and kitchen equipment should be separate. Why? To avoid any lye, soap residues or essential oils getting in your food. I picked this idea up somewhere and even though I could find no evidence to the contrary, I stuck by it religiously.
These days I feel a bit more relaxed about the idea though. If you very thoroughly clean your silicone molds and other equipment I don’t see any scientific reason to not to use them for cooking. If you’ve heard otherwise, let me know as a comment down below.
What about lye on my bakeware
Lye, Sodium hydroxide, is a caustic substance that does not absorb into the inorganic polymers that silicone kitchenware is made of. If you’re meticulous about cleaning then you won’t be harmed by lye or accidentally end up with soap in your cake.
Did you know that lye is used in dilute amounts to make traditional pretzels? They’re dipped in it before they’re baked and give that characteristic sheen. In this case the Sodium hydroxide reacts with CO₂ and water in the baking process and is converted into a very safe-to-eat carbonate. I wonder if the cooks re-use their lye-solution pots and pans for other things though. I’m leaning towards yes.
Clean scents off thoroughly
Silicone does have a tendency to pick up scents, be they essential oils or fragrance oils, so you should be careful. In the first place, you probably don’t want your blueberry muffins smelling or tasting of peppermint soap. It probably wouldn’t be appetizing and in the case of many fragrances, won’t be good for you either.
If your mold smells of anything, clean it before using it to cook in. Advice on cleaning scents from silicone molds include soaking in salt water, soaking and cleaning in baking soda (bicarbonate of soda), or heating to evaporate the essential oils. Sometimes the scent will disappear (evaporate) with time if the mold is left sitting out. The bottom line is, if your mold smells of anything at all, don’t use it for cooking.
Wood can work as a mold and to insulate
After silicone, wooden molds are the most popular in soap making. They come in standard sizes for medium to large batches, tend to be made of non-treated pine, and will also insulate your soap as it hardens. The wood acts like a blanket to keep the soap warm and to guide it into gel phase.
For many years I used wooden boxes to place my silicone soap molds into. It was only to keep the soap insulated though. You can see a photo of how that worked above with wooden lids just behind and ready to be fit on top. I’d put a towel over the box before the wooden lid just to minimize drafts around the top. I could have used the wooden boxes on their own though had I constructed the boxes a little differently.
Wooden soap molds for large batches
Large wooden boxes are great soap molds when lined with grease-proof/baking paper. The paper stops the soap from sticking to the wood. Getting the big slab of soap out can be tricky though. You can use the overlapping flaps of paper help to lever the soap out but with large blocks it’s not enough. That’s why most wooden molds are designed for the sides to be disassembled and/or the bottom to come off. Without this feature it could be difficult to get soap out without damaging it.
If you’re comfortable with wood working or know of someone who is, you can make a custom soap mold suited to your needs. I’ve seen them small enough for a 1-lb batch and large enough to fill half a table. There are also plenty you can buy too.
For these larger molds you can also get impression mats to set at the bottom. These are silicone sheets that you can cut down to fit your mold exactly. Impression mats come in various patterns and leave a pretty 3-D pattern on one side of the soap.
Although not wood, you can also find synthetic/Polyethylene molds in the same style as these wood molds. They sometimes come with mylar liners.
Metal Soap Molds
When it comes to using metal containers as soap molds you have to be very careful. Stainless steel is fine but avoid cast iron, aluminium, tin, or copper. That’s because those metals will react with the lye, release harmful gases, and potentially turn the metal black and ruin your soap. Not to mention the pan.
I’ve heard somewhere that in the past self-sufficient families would use their bread tin as the household soap mold. You can too just as long as yours is stainless steel. As with wooden molds, make sure to line the stainless steel container with baking/grease-proof paper to stop the soap sticking to the sides.
Another fun idea would be to pour a soap directly into a stainless steel tin as a product. A soap making pal of mine does that for a shaving soap.
Recycled Soap Molds
Name a type of food or product packaging and it can probably be converted into a soap mold. Especially if it’s made of sturdy paper or plastic.
In my classes I offer the choice of paper milk cartons that I’ve rinsed out or plastic takeaway containers. You know the kind that Chinese or Indian food gets delivered in? Both are perfect and can give plastic waste a second life.
In the case of takeaway containers, you can save them to use again and again. Just make sure to line them with appropriate paper to stop sticking. With paper cartons, you rip the sides down to get your block of soap out. In both cases you’d cut your soap into bars with a kitchen knife.
Other things that can be made into soap molds, although you will often need to line them with baking or grease-proof paper:
- Cereal boxes turned on their side with a large panel cut out
- Tetrapak juice and soup boxes (no lining required)
- Yoghurt pots
- Ice cream tubs or boxes
- Shoe boxes
- Pringle cans (no lining required)
Plastic Soap Molds
There are so many plastic and acrylic soap molds out there that I just want to cry. Beautifully designed with patterns and shapes perfect for all manner of soaps. The thing is that they’re designed more for melt-and-pour soaps, or even bath bombs, than cold-process soap recipes. Unless your recipe is made up of very hard oils, or has added Sodium lactate or salt to harden them up, it’s a nightmare to get soap out them.
Let me tell you a story about the pretty picture of soaps just below. When I first started my soap making business I found these amazing triple spiral designs perfect for the Isle of Man. The three legs of Mann is the Island’s symbol and we even have a 4000 year old triple spiral engraving on a stone outside Laxey. I just couldn’t get the darned things out of them!
I’d let the soap sit in them for weeks, tried chilling and even freezing the soap. Still around 50% would come out with the spiral design ruined. Do you see the round soaps sitting behind the spiral ones? I literally cut the tops off so that they’d at least look nice.
My advice: avoid plastic soap molds unless there’s a way that you can line them. Not only have I ruined a lot of soap with them but I’ve broken many of the molds just trying to get the soap out.
Custom Soap Mold Ideas
I’ve already touched on a couple ways that you could create custom soap molds. You could make wooden style boxes of any size and could customize waste packaging to create free soap molds. There are even more ideas you could use too.
For a honey or beeswax soap, line the bottom of a loaf or tray soap mold with bubble wrap. It will give the tops of your bars a honeycomb effect. Use the same idea but with textured vinyl wallpaper or stencils for pretty and whimsical designs. You can also make your own silicone impression mat like this one made with lace.
If you’re feeling really crafty, you can also create your own custom silicone soap molds. There’s a great piece over here detailing how one hubby was roped into making a Buddha soap mold for his wife. It’s pretty clever but a little labor intensive. If you have the dosh, there are folks on Etsy and other places online who can create custom silicone molds for you too.