Using Expanding Foam Insulation To Make A Mold?

[GMer56]

I just came up with a crazy idea that may or may not work, so I'm asking all of you.
Could someone create a mold using expanding foam insulation?

I.E. suspend the part in a bucket, spray some foam around it and let the expanding foam do what expanding foam does.

 

[dsilver668]

I just came up with a crazy idea that may or may not work, so I'm asking all of you.
Could someone create a mold using expanding foam insulation?

I.E. suspend the part in a bucket, spray some foam around it and let the expanding foam do what expanding foam does.

Nice idea but the major issue is detail. Expanding foam is really sticky. It also dos n't bring out the details like you would normally get. our origional master would be destroyed in the process.

Now for some good news. The foam is somewhat flexable but still is pretty ridged. Model Railroaders use it for mountains as a base the lay down rock castings and plaster for the ground on top. Don;t ask me how I know this, as I will deny any wrong doing...
My thoughts are this. It is ridged and sticky until dry. You could use your regular molding materials i.e. latex rubber for a thick coat around the master. Now place it in a bucket or tray. use the medium expanding foam to create the base structure to support it instead of heavy plaster which can shrink or crack over time. Now you can flash cast to your hearts content. essentially it is replacing a material in the process. You may want to cover the rubber from the model with seran wrap "cling wrap" This way you can remove the casting and peal back the rubbber and replace it to the foam structure. Once the foam is dry you won't need the cling wrap any more. expanding foam isn't cheap but it probably will hold up better to handling and bumps etc. since it is also designed to go into a house wall it will stand up to sitting in a hot garge over the summer and such. Also if you live ina humid area you won't get mold or anything else growing on it like I have had happen to some plaster castings I have had.
Just my two cents hope this helps!

 

[falcon NL]

Would this work? Maybe
Would it be a good mold? NO
Would it give me more then one pull ? Most likely no

Expanding foam, is a foam that works on a chemical base. Is trapping air inside the foam, with create air pockets. And the last thing you want in your mold is air bubbles/ air pockets in this case. The other thing is that insulation foam is pretty brittle so it would be like that it would break fairly easy.

But if you think you can pull it off [pun intended] go for it!

 

[HeavyGunner]

Now for some good news. The foam is somewhat flexable but still is pretty ridged. Model Railroaders use it for mountains as a base the lay down rock castings and plaster for the ground on top. Don;t ask me how I know this, as I will deny any wrong doing...
My thoughts are this. It is ridged and sticky until dry. You could use your regular molding materials i.e. latex rubber for a thick coat around the master. Now place it in a bucket or tray. use the medium expanding foam to create the base structure to support it instead of heavy plaster which can shrink or crack over time. Now you can flash cast to your hearts content. essentially it is replacing a material in the process. You may want to cover the rubber from the model with seran wrap "cling wrap" This way you can remove the casting and peal back the rubbber and replace it to the foam structure. Once the foam is dry you won't need the cling wrap any more. expanding foam isn't cheap but it probably will hold up better to handling and bumps etc. since it is also designed to go into a house wall it will stand up to sitting in a hot garge over the summer and such. Also if you live ina humid area you won't get mold or anything else growing on it like I have had happen to some plaster castings I have had.
Just my two cents hope this helps!

Yes! This will work. You could totally use the foam as a jacket. But you could not use it as a mold itself. The rigidity of the foam and it's hardening poroperties would work good for a mold jacket, but not for the mold itself. Check out the mold making tutorial in the molded section and you should figure out what I'm talking about.

 

[GMer56]

I knew this was a crazy idea
Thank you for the input, I might try it, I'm gonna need the foam anyway to fill my weapons anyway.
I just though of a problem, if the foam on the inside and outside of the part expand at different rates, there may be warping unless the part is reinforced the heck out of (or if it is closely monitored).

This stuff is $30 a pop, but it comes in a six-pack and is made from renewable resources (so it claims)
http://www.homedepot.com/webapp/wcs/stores...100662141"" target="_blank">Home Depot's Foam Isulation</a>
Plus the stuff is supposed to cure in 6 minutes.

Then there is Lowe's "Great Stuff" at $4 a can, which is cheaper, but not as environmentally friendly.

 

[Ithica]

Ok I am going to speak from experience here.....I thought about the same idea...kindda. I thought about using it for a shell rather than a mold. I put a solid box around the mold and began to fill the box with the foam....the box expanded greatlt which means it was pushing hard enough to fill in gaps. I ran into a few issues with this. One the gaps weren't all filled in (don't know why) two it didn't cure completely I believe because it was so thick and three it was a fail. Maybe someone else will have better luck.

Ithica
Dave

 

[GMer56]

Well, I could solve the sticky solution by coating the part with Crisco, or any other cooking oil.
Maybe there wasn't enough foam to fill the gaps, once I get some Good Stuff I'll definitely try this with a hand plate.

 

[Iceman065]

If you are going to use Great Stuff or any other kind of expanding foam, forget using a release agent because it wont do a damn thing. The expanding foam is made so that it can be used to stop any and everything and is made to be used in wet damp and slimy places. Also treat it like a toxic version of Bondo. Do it somewhere very well ventilated and work in small batches. Ithica's problem was that he used to much of it and it didnt cure correctly because of the volume of material used. You have to use small batches and let them completely cure before you add more to it. So plan on doing layers at a time because the foam will expand and push against things or even crush things if your not careful while it is curing. But when it has set completely it can and very well might, shrink slightly.

And if you use it as the mother mold (the harder outer mold that holds the inner soft mold that has all the detail) then make sure that you put in dividers that are ridged but also can be bent like a thick platic. That will allow you to put them onto the foam as it dries and then flex and roll them off of the foam once it has cured completely.

Saftey tips. Wear rubber gloves and get some finger nail polish remover just in case you get some foam on your skin. Since Great Stuff is petrolium based it will take it off of your skin pretty well, instead of trying to chip it off over the course of a few days. And remember, do this in a well ventilated area, the fumes from the foam curing can be bad for you.

**EDIT**

I re-read the DIY Packing Tape Body Molds and Castings by Sean Bradey and realized that yes, you can actually use petroleum jelly as a release agent. Sorry for the mistake!