Lightweight Inexpensive Insulating Box for Soap Molds

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user 49910

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Mar 13, 2021
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Happy Standard Time Day Peeps!

This week I thought I would share the very effective, lightweight foam mold I made for my Tall & Narrow Silicone Soap Mold.
I initially thought of making it solely to reinforce the sides in the middle where the mold might have a tendency to bulge out from the weight of the soap batter.
Then, upon deeper thought... yes @Johnez and @Zany_in_CO & @ResolvableOwl I am capable of it in rare instances! 🧐

The insulating foam box is made of extruded polystyrene foam board, such as used in construction. I used the brand name Foamular© made by Owens Corning. I purchased a 2' x 2' x 1" piece at Home Depot. However, any type of EXTRUDED polystyrene foam will work, but it must be the extruded type because it is so much stronger and easier to cut and work with compared to expanded polystyrene; which is a the regular bead-type of foam we see in packing electronics, appliances and such. It cuts like butter to be honest, the trickiest part is keeping the knife at a 90 degree perpendicular angle to the foam board. The expanded type of polystyrene the knife will catch and the little beads will bunch up too.

along with an extendable utility knife
Screenshot 2021-11-07 093116.png
& Gorilla Glue
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Measure the outside dimensions of the mold you want to support and insulate. You don't have to be exact or precise, within 1/8" or 3mm for you folks in Europe. The Gorilla Glue is actually a type of polyurethane glue and will bond the foam together very well with no fumes or flammability to it. It works with the humidity in the air to cure, gradually getting slightly foamy in the process. Wear disposable gloves while working with it because it will stick to your skin rather tenaciously if you get any on it.
Let it cure for about 8-12 hours with the boxes sides first glued, the attach the bottom. Use masking tape to temporarily hold the pieces together until the glue is set. The top piece is loose and used to cover the mold while the soap is curing. I use a piece of plastic kitchen wrap to cover the loaf and then place the lid on top. Then put a weight of 1 to 2 pounds or .5 to 1Kg for you Europeans.

The soap heats up well in this type of foam box and maintains it's heat for much longer compared to using towels, blankets or Reflectix. It has an R Factor of 5 which is the equivalent of 2.5 inches of blown fiberglass or 2 inches batt fiberglass insulation.
It weighs a total of 4-1/2 ounces minus the mold. So it is lightweight and easy to use and store.





An easy project to do in an hour or so. Plus with the 2'x2' size board, you can get at least two insulating boxes out of it.

Let me know what you think! So far it's been working great for my bar soaps and the gel process lasts much longer than previously for me.
What a lovely colour! 🥰😜

Anyway, great idea, good execution, no unnecessary perfectionism. Might your noble R value reward you with intense & complete gelling, and one or another glamourous soap volcano!

Extruded styrofoam is a lot of fun, though I'd prefer a hot-wire cutter more over a knife (not only for the sounds a knife makes). Haven't played around with it for a too long time.

Up to which temperature is your foam specified?
no unnecessary perfectionism
Ah yes, the Irish side of me had to tell the German side of me to just "Get it done!" Too many times my perfectionism has caused excess stress, high cortisol levels and such.

I thought of making a wire cutter, but then I would have to mess with that and find a transformer I could use, some Nichrome wire, handle, wire, patience, etc. So I used the KISS principle. Besides it suits the purpose for which it was made, but I don't believe the Smithsonian will put it in any of their showcases!

Regarding the temperature from the PDF Data Sheet: Service Temperature, maximum °F (°C) - 165 (74)
Using my infrared thermometer, the highest I've read has been around 149° F, and it holds that range for about an hour or so and then slowly drops over 4-5 hours. After 6 hours it has been reading around 120° F or so, after about 18 hours it is still lukewarm to the touch.

Might your noble R value reward you with intense & complete gelling, and one or another glamourous soap volcano!
It does gel very well, even into the squared off corners of the mold! No gel rings or other marks of an incomplete gel process. No volcanoes yet... I've been doing my CP at around 100- 110° F to avoid quick trace and such. The FO's I use are blended with the melted oils first before adding the lye solution, which I have found to be much easier to work with regarding quick trace issues.
I've never doubted that you're capable of deeper thought Prof. 🤣

This is great tutorial. For one it's thorough, leaving no questions up in the air for people like me to madly wonder about. For another, you list the specific tools and materials and reasons for them. I hate it when it's "glue" that we're using-there are *many* types-a specific brand you mention too-even better!

I've got myself a TnS mold, I have yet to use it, except to rest curing soaps lol. Definitely bookmarked for future use.
Okay, drum roll.... some photos of the famous pink foam insulator in action! Ta-Da!

Notice the slight bulge in the center of the loaf as the soap gelling heats up the soap and causes it to slightly expand in the first 2 photos.
I do use the foam lid too, putting weight on it while the gel process is working and to ensure an even top to the soap loaf.





Yes, I always overfill by about a 1/2 ounce or so. That way I have a nice even loaf with even ends and sides. I use a long 10" meat carving knife with the dull side against the top and gradually scrape off the excess soap. That makes a little soap ball to test and mess around with, the loaf goes into the 12-bar wire slicer next.


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