Silicon mold question

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soligen

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I made a mold using acid cure silicon caulk. Depicted here:

http://www.penturners.org/forum/showpost.php?p=1066515&postcount=30

I lined the negative of my form with some plastic wrap, which is now stuck really good to the silicone. I kind-of peals off, but tears away before I get very far. I've pulled off the loose bits, but have only removed maybe 10% of the plastic wrap. I tried some acetone hoping it would disolve the pastic wrap, but no.

Will having the plastic wrap stuck in the mold pose any issues for me? Will it come out with the first blanks? Will the PR disolve the plastic wrap?

I need to know as I have a PITH pen riding on this mold :biggrin: - or do I need to punt and get another mold.
 
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The first time i made a mold, i couldn't get the plastic wrap out of the very bottom of the mold so i decided to cast it anyways. I was using alumilite and so i poured as usual and i was lucky enough for the plastic wrap to stick to the bottom of the blanks and i just turned it off. I dont know what pr would do to it, but i know that if you are not carefull when you pull the blanks out of the mold, you will tear your silicon which is the worst thing in the world!!!
 
The same thing happened to me and I just kept at it until I got it all off. I doubt that it will be a problem and would likely come off with your first cast or two.
 
I made my first mold the other day and forgot to wrap the center piece with saran wrap.I thought of it after I added the silicone.It was a big pain to pry away fron the wooden center piece.So I wonder which one would be better Wrap or not wrap?Both sounds difficult to me.I did have to do some repairs on my mold but it looks good now.I just haven't had time to try it yet.
Toyotaman
 
Craftdiggity said:
The same thing happened to me and I just kept at it until I got it all off. I doubt that it will be a problem and would likely come off with your first cast or two.
Click to expand...

OMG - maybe yours was easier than mine. I dont think its possible - or would take many hours - more than the mold is worth.

Sounds like its not going to be an issue. If it doesnt work out I guess I'll just toss it make the "cutting board" style of mold instead.
 
toyotaman said:
I made my first mold the other day and forgot to wrap the center piece with saran wrap.I thought of it after I added the silicone.It was a big pain to pry away fron the wooden center piece.So I wonder which one would be better Wrap or not wrap?Both sounds difficult to me.I did have to do some repairs on my mold but it looks good now.I just haven't had time to try it yet.
Toyotaman
Click to expand...

I think if I did it again I would try rubbing wax all over the wood instead.

Hmmmm - maybe I'll make another just to try this out.
 
I've never saran wrapped my masters. Just waxed the wooden masters, glued them down to the form bottom, built up the frame, and poured the silicon in.

You do end up with grain lines in the mold and hence your blanks, but you'll turn those away anyway.
 
jason_r said:
I've never saran wrapped my masters. Just waxed the wooden masters, glued them down to the form bottom, built up the frame, and poured the silicon in.

You do end up with grain lines in the mold and hence your blanks, but you'll turn those away anyway.
Click to expand...

Jason,
I don't think he is talking about normal pourable silicone. I think he was using silicone caulk from the tutorial in the library.

This type of mold was the first I ever constructed and I don't remember the saran wrap sticking at all. Maybe it is the type of caulk that I used. I still use that mold today for the larger casts (~1").
 
Yep, silicon Caulk.

Has anyone tried a 3/8 round over bit on 2 corners of the blank negative to give the bottom of the mold cavity a curve? Just to save a little resin. It would make the blank a little off balance until turned round. Seems to me the balance would not matter much - just wondering if anyone has tried this.
 
soligen said:
Yep, silicon Caulk.

Has anyone tried a 3/8 round over bit on 2 corners of the blank negative to give the bottom of the mold cavity a curve? Just to save a little resin. It would make the blank a little off balance until turned round. Seems to me the balance would not matter much - just wondering if anyone has tried this.
Click to expand...

What I did with mine was use a piece of PVC pipe cut to length. All but one side of my blanks out of that mold are perfectly round.
 
soligen said:
Yep, silicon Caulk.

Has anyone tried a 3/8 round over bit on 2 corners of the blank negative to give the bottom of the mold cavity a curve? Just to save a little resin. It would make the blank a little off balance until turned round. Seems to me the balance would not matter much - just wondering if anyone has tried this.
Click to expand...

This is exactly how the resin saver mold is constructed... You save resin if you don't fill the corners and make it just bigger than you need for the blank...

I round over two corners of most of the molds that I make.
 
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