Casting pot metal or lead - how to make the mould?

[pfillery]

I want to make a casting of an object in order to use it as the basis for a prop I'm working on. If I want to cast the basic shape in a low melting point metal (to give it some weight, and because I have it readilly available) but what can be used to make a 2 part mould that is suitable for this purpose ie can withstand the heat, reusable in case the first one fails, flexible so it can be pulled out easilly and simple for a very green noob to acomplish.

Can you use the heat resistant sikaflex/silicone type materials?

Is this clutching at straws.

 

[Viking]

Silicone rubber is good for low temp melt metals. Smooth-on offers Mold Max 60 which is ment for higher temp castings if needed.

Mold Max® 60 Higher Heat Resistant Silicone | Mold Making and Casting Materials Rubber, Plastic, Lifecasting, and More

 

[robn1]

Silicone is used for metal casting, like tin and pewter. Some silicones can withstand up to 500F.

 

[Luke0312]

Also robstyle gives good advice here as far as practicing casting metals.

http://www.therpf.com/f9/easy-cast-small-metal-props-150858/#post2308634

 

[robstyle]

Before you get into metal casting, does the part really need to be metal? A high impact plastic may be a much safer and simpler alternative. That is of course pending the part you are trying to mold and cast.

 

[pfillery]

Silicone rubber is good for low temp melt metals. Smooth-on offers Mold Max 60 which is ment for higher temp castings if needed.

Mold Max® 60 Higher Heat Resistant Silicone | Mold Making and Casting Materials Rubber, Plastic, Lifecasting, and More

Does this still work for full 3d casts? ie where I want to cast both sides of an object in one, as opposed to just one side as shown in the link?

Plastic may be an option, or some sort of resin, but I like metal bacause of the weight and feel of it. Plus I want to use materials readilly available, and casting/moulding resins are not really over the counter items in Australia.

 

[Viking]

Does this still work for full 3d casts? ie where I want to cast both sides of an object in one, as opposed to just one side as shown in the link?

Plastic may be an option, or some sort of resin, but I like metal bacause of the weight and feel of it. Plus I want to use materials readilly available, and casting/moulding resins are not really over the counter items in Australia.

Yes two part molds are fine. When casting hot metals into silicone, only use block molds, as glove type molds are too thin causing the heat to radiate outwards and will burn you. I casted a lead skull into a two part mold years ago (I'll post a pic later)

If you can get away with using a resin, I would do that. Not only is resin a lot safer but will pick up much better details.

 

[robstyle]

The issue your going to quickly run into with metal casting into a two part mold (not one piece / open face) is the metal will start to set before its filled every void. This is also a problem trapping air pockets as the metal will fill or block channels cut into the mold. It may not happen all of the time but it will happen most of the time. This is why the lost wax method hasnt changed much in thousands of years.

Easy solution is to post a picture of what your trying to cast.