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In Remembrance
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Discussion Starter · #1 · (Edited)
This is an attempt to make a mold using silicone chalking and Great stuff foam. The first try failed because I put the silicone on all at once and didn't dry properly. The next time I put the silicone on one tube at a time and allowed one or two days for it to cure. A very thin coating of vasiline was used as a release agent. If you use to much the silicone will not stick and will slide off.
The silicone was then cut making a front and back half. I very carefully used my finger to release the mold from the skull. Next the two halfs will be placed in a box and covered with Great Stuff to form a mother mold for support.
This is as far as I have gotten, with a little luck it might work.

http://www.hauntforum.com/album.php?albumid=713

link to album with the progress pictures.

 

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That looks great so far, but I am confused. Are you going to put the great stuff on the outside... [quote: "Next the two halfs will be placed in a box and covered with Great Stuff"], or fill the mold with the great stuff? I can't wait to see how this comes out. Keep us posted.
 

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I'm anxious to see how this works for you. I attempted something similar a few years ago, but I had much less knowledge about this than you, and needless say, I had a huge mess and a screwed up skull, lol. I hope this works out for you.
 

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That looks great so far, but I am confused. Are you going to put the great stuff on the outside... [quote: "Next the two halfs will be placed in a box and covered with Great Stuff"], or fill the mold with the great stuff? I can't wait to see how this comes out. Keep us posted.
From what I read on the first pic in the album I think the greatstuff will be on the outside to act as the mother mold.
 

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In Remembrance
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Discussion Starter · #5 ·
Well in fact I will be using GS as the molding material too. When I am done I should end up with two blocks of GS with the silicone mold half in each. The two blocks will then be put together and held in place with some heavy rubber bands and then GS will be put into the mold and allowed to set. After which the two halves will be taken apart and the new foam skull removed. I am sure some more pictures will help to explain what I am trying to do.
 

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Sounds interesting.. How many skulls do you think a can of GS will make?
 

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Yep, I will wait for the pics cuz I am really confused. But I am a picture kind of learner. LOL
 

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Did you learn this mold technique somewhere or is this is something you are creating. I am just as confused as how something as brittle as great stuff will make a mother mold? Not saying it can't be done but not sure why. You could easily make a rubber mold from a small jug of latex and shredded cotton pads as a reinforcement agent in the latex. Keep us posted, I am always up for learning new tricks.
 

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This looks good to me. But I think you should use plaster or something else for for the back up mold. GS never seems to quit expanding, from what I have seen. Plaster might even be cheaper. But this is a good idea. Look forward to seeing how it comes out.
 

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In Remembrance
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Discussion Starter · #10 ·
Thanks for all the feedback everyone.
Not sure how many skulls are in a can of GS, and yes I know that two part foam is better but this is a low budget experiment.
You may have a good point about the GS as a mother mold and plaster does sound like a good idea. Latex is expensive and what I have is needed else where.
At the moment my worry is that if I use GS as the mother mold it may deform the shape of the mold when it expands against the mold and the box. I may have to fill the mold first in order to hold the shape during the making of the mother mold.
Maybe I should run some simulations in the holodeck first.
 

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Thanks for all the feedback everyone.
Not sure how many skulls are in a can of GS, and yes I know that two part foam is better but this is a low budget experiment.
You may have a good point about the GS as a mother mold and plaster does sound like a good idea. Latex is expensive and what I have is needed else where.
At the moment my worry is that if I use GS as the mother mold it may deform the shape of the mold when it expands against the mold and the box. I may have to fill the mold first in order to hold the shape during the making of the mother mold.
Maybe I should run some simulations in the holodeck first.
You can do a lot better things in the holodeck. Get Spock to run the test!
 

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I would just leave the skull in the mold and shoot the GS around it to make the mother mold. That way expansion won't be such an issue with deforming the latex mold.
 

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Discussion Starter · #13 ·
I would just leave the skull in the mold and shoot the GS around it to make the mother mold. That way expansion won't be such an issue with deforming the latex mold.
The skull is an old plastic model and is fairly heavy and I would prefer not to cut it. And the mold is made with silicone, not latex.
 

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In Remembrance
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Discussion Starter · #14 ·
I think I may fill the mold with plaster and do a GS mother. Let you know how it goes.
 

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Discussion Starter · #16 ·
Results of my experiment
WHAT WORKED
Using the silicone to make a mold (100% silicone selent) worked well. Its flexible but not as much as latex. I would think it would work well to make small one sided parts for decorations on a wall or flat surface. The silicone is readily available to anyone and is fairly cheap at about $3.50 a tube. It should be applied in layers and allowed to cure.

WHAT FAILED
Making thick items (more then one inch) is the main issue. The outer layers will cure leaving the inside raw and pron to shrinkage and deforming. In making the mother mold with GS I didnt fill the cavity of the silicone mold and as the GS expanded it deformed the silicone mold. Filling the mold with something (plaster) should prevent this. Possiblely making the mother mold with plaster might have worked better also.
RESULTS
Great stuff is usable but has its limits and has long as you stay within those limits it is workable. As long as fine detail is not needed and care is given to layering the GS instead of making one large fill, its a workable product for some projects.
Two part foam is better by far and latex or more flexible silicone (dragon skin) would be the best way to go. But with limited funds and resources I think it would be possible to get usable results with the silicone selent and Great stuff foam.

Thanks for all the input.


 

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If you add about 4 drops of glycerine and a couple drops of acrylic paint per ounce of silicone, you will find that it dries nicely from the inside out.

ive made several successfull (more than 1'' thick) silicone molds, but I have always used the glycerine and paint and 3 total layers for a nice thick mold.

I use a different color for each layer

if you spritz the mold with water before and after you spray in your greatstuff you will find it will give you a better cure and you can do it all at once.

its a great solution if you dont need perfect detail or consistancy in size, ive had some finished skulls shrink to half the normal size before, but they retain most of the detail.

if you need consistancy in size and detail, do it right and use 2 part marine foam.

you can buy a bottle of glycerine at your local drug store, I bought mine at walgreens

here is a project that I used some of the skulls on
inspired by Steve Hickman
 
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