Question: Creating silicon molds

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While i have read and viewed various helps from alumilite and also this forum, i cannot find any information specific to the creation of silicone molds for say, the engraved side of an action for example. Or the engraved rear portion of a barrel. What is used to "box in" a localized area? Can plasticine be used or is their something else better suited? Will pouring silicone resin onto a metal surface to produce a mold damage or alter the surface finish of the master item? Ie: rust blue, ink, lacquer etc?
 

John B.

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Yes Plasticine ( modelling clay in the US) can be used but it must be the sulfur free type or it will break down the silicon.
You can also make a container dam using cardboard and Scotch tape.
 

jerrywh

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I have made hundreds of silicone molds for every muzzle loading gun part imaginable. Silicone will not hurt anything. The best information you can get is available on the Polytek web site.
https://www.polytek.com/product-type/silicone-mold-rubbers You can get info on mold making of any type there. The platsil is the best for your type molds. Do not use the tinsil base. You will need to vacuum the silicone before you pour it to get perfect molds. You will need to learn some facts about wax also.
When I answered this I was thinking you wanted to cast some parts. That is why I mentioned the wax deal. The molds I make are for casting.
 
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Might try the 'sulfur free' modelling clay...good to know silicone doesn't hurt anything. I never knew that their were so many applications for molding beyond preserving fine hand engraving. Many thanks.
 

Memorymaker

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Some people use Sculpty Clay ......... you can build your model then bake it to harden it so you can use it over and over without it changing
 

Southern Custom

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Doesn't someone offer a kit designed specifically for this purpose. I thought I recall seeing one at Brownells or somewhere. I know there are quite a few folks here making plastic castings so I'm sure someone will pipe up.
 

John B.

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For many years Mike Bissell made all the molds and castings for FEGA, thank you Mr. Mike.
He retired from that office but you can rely on any information he cares to share.
I believe Bert Edmonston now holds that FEGA office.
 

gtsport

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Go to Hobby Lobby with their 40% off coupon. They have two types of casting rubber, clay, casting resin, in kits and separately. It's in the aisle with the air brushing stuff.
 
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Resin Casting

Ok, so i created a dam wall with modelling clay, poured Alumilite Quick Set PTV Silicone rubber to about a 1/4" deep and i am glad to report success! I did not disassemble the rifle and the resin made its way into some unwanted areas (joints between mating components) but fortunately was no big deal.
I figure that i need to create a wall around the silicone mold in order to cast the resin. What is the best way to trim up the rough edges around the mold? Ie, a hot wire? I'm thinking that sticky tape around the trimmed up edges will be enough to create a dam wall? Any thoughts are greatly appreciated!
 

mitch

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could you post a photo of what all you're dealing with? the advice you need may be somewhat dependent on the specific situation. not every trick works everywhere.
 

JJ Roberts

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southern lights,When making castings of my engraving I use Smooth Cast Inc.Easton Pa.www.smooth-on.com easy to use and they may sell it in Australia,I recently found it in an local art store here in Virginia. J.J.
 

Chujybear

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trim with an exacto.

silicone can take a lot of heat.. but cuts nicely.. i make my molds w hot glue and card stock, depending on the scale
 
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The attached images shows a 1/4 thick mould of an engraving...(not my engraving), with rough edges because of the modelling clay dam walls not being perfectly made. I dont suppose tidying up the edges is rocket science (or brain surgery for that matter), but to know what processes have worked best for others would save me some time in discovering "best practice." There are probably a few other areas that need cleaning up too, like where the screw was....
 

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After leaving my silicone moulds on the bench for a few weeks i have noticed that they seem to be sweating.... just a little. Is this normal? The exacto knife works well.
It's great to know some of the moulding product options that have been successfull... thanks for sharing.
 

mitch

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After leaving my silicone moulds on the bench for a few weeks i have noticed that they seem to be sweating.... just a little.

did you leave a male & female mold pair sitting close to each other? that could explain the sweating...
 
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