# Soap Molds



## Absinthe (Feb 9, 2010)

I figured that someone here would have a great answer to this question, so here goes:

In another aspect of my hobby life I make soap. Part of that involves making a mold out of wood and pouring the soap into it while it hardens. Most of the mold designs are simple butter press wood molds. 

Many people use some type of freezer paper as a liner so that the raw soap batter does not 1. soak into the wood, damaging the mold, and 2. Stick in the mold.

Here is the question:

What would be a good finish for such a mold, that would make the idea of lining unnecessary? Or is this a pipe dream?

Absent that what is a good finish for such a mold that might protect it from spills and splashes. 

The variables are this:
Oils and lye are mixed together and mixed until a particular consistency is reached. They are them put into the mold to be insulated hoping their reaction reaches a critical stage (called gelling) that can potentially reach temperatures in the range of 150F and up. Until this reaction is complete the caustic (lye) is still pretty active and caustic. Things such as organic waxes and oils are saponifiable, meaning that they would in fact become part of the soap.


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## Tony B (Jul 30, 2008)

I make molds for epoxy castings. I use them to make the missing pieces on antique picture frame molding.
I use a latex molding material that can be had at any large hobby shop. If the casting will be large and heavy, set the mold on/in sand to support it. Epoxy, plaster and other thimgs will not stick to it. As for replication......the epoxy castings will even show the pores in the wood grain. 
Each mold is good for several castings. If you need to make a mold for 50 or more castings, just imbed gauze bandage tape into the layers and boil (vulcanize) the rubber and it will last a while. 
Latex molds are easy to make. I once made a mold of a woman's breast for an art class.


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## woodnthings (Jan 24, 2009)

*Yeaaa? prove it!*

pics? :laughing: bill


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## Tony B (Jul 30, 2008)

Sorry Bill, it was lost during Hurricane Katrina. 
I know, I know, it sounds like the old "the dog ate my homework" routine.
It did make a nice conversation piece on my shelf.


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## Tony B (Jul 30, 2008)

Absinthe said:


> ...Absent that what is a good finish for such a mold that might protect it from spills and splashes.


Have you ever though of making fiberglass molds? They are also easy to make and will last forever. You wax them with a mold release and your soap will pop out shining like a mirror.


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## Absinthe (Feb 9, 2010)

I like all these responses. Let's see if I can address them all without missing any:

I should have started out by saying that I will indeed be making some silicone mold liners and perhaps even single cavity molds. Commonly people use molds and then add mold liners. They are either folded from freezer paper or made from some permanent material such as silicone, HDPE, Corrugated Plastic and so forth. 

I have yet to hear about or try fiberglass or latex. Though I would fear latex to be reactive with the caustic, especially since it doesn't do well with oils in general, I am not certain it would be appropriate for soap (But I could be wrong and will have to research)

Fiberglass on the other hand, intrigues me, where could I find out more on that subject. I guess I would do it like makign a sink right? Use the stuff from the autoparts store?

All that said, my original question has apparently been misunderstood. What I was wondering about was a "finish" or two finishes actually. One to keep the mold protected from light splashing and spattering of the oil/caustic mixture, and the possibility of one that would work in place of a liner. A few things came to mind. The first was "Silicone Oil" the stuff that makes woodworkers cringe when someone uses lemon pledge on one of their pieces. I wondered if it was so pervasive and hard to get out of wood perhaps it would make a nice permanent protective finish. The other that came to mind was of course polyurethane, which I am always afraid to mention around woodworkers as it tends to get me yelled at. However, perhaps in this case it may be appropriate. However, can it actually be cured to a hard finish instead of that sort of always semi-soft stuff. 

Please forgive me if I have crossed any lines here. The last time I was involved in anything even mildly related to a forum for woodworking was on alt.woodworking and I am certainly sensitive to the differing camps, hopefully I haven't stepped into any of them now.


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## Gene Howe (Feb 28, 2009)

I use McClosky's Man-O-War. It's a marine varnish and holds up well to sun and salt water. How it would react to your ingredients may be another story. Your temp.s shouldn't pose a problem, though.
Some time ago, I was commissioned to make several different soap molds. For the boxes I used 1/2" Baltic Birch plywood and made an egg crate like container to hold 24 bars of soap. The bottom was detachable so extraction was easy. 
For the designs, she sent me 6 different rubber stamps which I used to make an inked design on copper. Then I chased the design, glued the copper to a piece of hardboard and poured in a rubber mold mixture. The resulting mold was placed in the egg crate to make the designs in the soap. 
I don't know what she used to line the Baltic Birch sides.

Gene


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## Absinthe (Feb 9, 2010)

Did the egg-crate-like thing fit inside the baltic birch mold box?


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## Tony B (Jul 30, 2008)

Absinthe said:


> ..........I have yet to hear about or try fiberglass.........Fiberglass on the other hand, intrigues me, where could I find out more on that subject. I guess I would do it like makign a sink right? Use the stuff from the autoparts store?........


To find out how to make fiberglass molds , go to the library and there are plenty of books. Might also look up fiberglass boat repair. 
Fiberglass can be bought at automotive parts places and marine suppliers. 
And yes, same as making a sink, a boat, a swimming pool, a car and just about anything. It is aesy to do but messy to learn. Once you get used to it you figure out cleaner and neater ways to use it. Wanna copy you friends boat? Just wax the heck out of his hull with a mold release wax, lay up new fiberglass on top of it and when it hardens, just pop it loose. Pretty much that all there is to it. You will also pick up every scratch on his boat no matter how minor unless you really level and fair out everything. It gets more interesting.....If you made a mold of his boat, spray gelcoat on the mold. Gelcoat is more or less a polyester paint. Then lay up the fiberglass. Kinda neat when you think that most boats start with paint job and they stick the fiberglass to it.
Once you get used to it you will agree, fiberglass is your friend.


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## Absinthe (Feb 9, 2010)

I have worked with the cloth and resin stuff they sell in the autoparts store, helping a friend do body work on his car back in the day. 

We soaked the fiberglass cloth in the goo and plastered it on and then smoothed it out and so forth. I have also seen plans for making a sink, in that you build the trough out of wood, then lay in the cloth and goo. I can't imagine how that would hold much detail... Or is there a resin that is thicker than the goo which would hold itself to cure?

Will it bond to wood if I paint it the way you said, or is that just to bond it to other fiberglass?


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## Gene Howe (Feb 28, 2009)

Absinthe said:


> Did the egg-crate-like thing fit inside the baltic birch mold box?


The egg crate was the mold sides and the rubber design fit down in the egg crate thingie and sat on the detachable bottom. As designed, the rubber design mold was supposed to come away with the bottom. 
I guess it worked fine, as she had her brother make a couple more just like the one I made.
Gene


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## Absinthe (Feb 9, 2010)

Yeah, Gene those are popular. They pay an arm and a leg for them too. I plan on doing some designs in plaster of Paris and silicone molding them to make either molds, or "mold bottoms" 

Silicone seems to be a real popular material of choice, but 2 part silicone is expensive as all get-out! So I am toying with a few ideas.


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## mdlbldrmatt135 (Dec 6, 2006)

I build plastic models and cast parts in resin for myself. I use the silicone for molds.

Check out

www.smooth-on.com

They have tons of products and their Technical staff are great to work with as well.


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## Gene Howe (Feb 28, 2009)

Absinthe said:


> Yeah, Gene those are popular. They pay an arm and a leg for them too. I plan on doing some designs in plaster of Paris and silicone molding them to make either molds, or "mold bottoms"
> 
> Silicone seems to be a real popular material of choice, but 2 part silicone is expensive as all get-out! So I am toying with a few ideas.


I seem to recall some chatter that the silicone molds deteriorate after several pours. No personal experience, though.
The egg crates are not expensive.....if you build your own. 
Gene


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## mdlbldrmatt135 (Dec 6, 2006)

they can if the pours are complicated, as the demolding process can stress them, otherwise it's time that kills them. It's also related to the silicone I use for the molds the castings are complicated so I use a really soft, flexible silicone for molds

I've got a few smaller ones that are fairly complicated for 1/35 scale figures and such that have gone bad after 2-3 years (and few castings) but some after a hundred or so castings in a few months. 

all I could say is call Smooth on and talk to them they'd be able to recomend something that'd could work for you if you want to mold things other than "brick" shapes.


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