Casting moulds and material

[Dalboy]

Ok there are going to be a few questions from me about casting. This one is about Moulds and the material that they are made from.
So what do you use for making the blank moulds, I have heard people using silicone. And also pieces of plastic pipe. What are your thoughts on these.
Also how big do you make them most that I have seen appear to be for making about 4 blanks after they have set and been cut.

 

[brody2123]

You can use silicone, but it will take ages to cure and probably won't last very long. I use hdpe sheet from ebay or loads of places on google. Cheap, stable, easy to cut and screw together and lasts for ever. Pvc pipe can be used but would use a release agent with them just to be on the safe side. Size wise, especially with the hdpe, you can do what you like really. All depends on how many you want to make of one cast. Just add a bit extra for trimming and Bob's you uncle.

 

[George Watkins]

I use rtv silicon, some people try and make them from the silicon you get in tubes for bathrooms etc but that isn't really suitable. RTV is a two part silicon which cures overnight and can be used the next day but its best to let it rest for a few days before use. I make a wooden forma then pour the silicon in, you can de-gas before pouring but i never find it necessary. the trick is to make your wooden forma as smooth as possible as any dents etc will be transferred into the silicon mold.

polythene sheet materials like hdpe and white chopping boards are handy for certain resins but wont last forever before the resin wont release and sticks solid, I get about a year from mine but I do cast a lot.

 

[Chilprufe]

I use rtv silicon, some people try and make them from the silicon you get in tubes for bathrooms etc but that isn't really suitable. RTV is a two part silicon which cures overnight and can be used the next day but its best to let it rest for a few days before use. I make a wooden forma then pour the silicon in, you can de-gas before pouring but i never find it necessary. the trick is to make your wooden forma as smooth as possible as any dents etc will be transferred into the silicon mold.

polythene sheet materials like hdpe and white chopping boards are handy for certain resins but wont last forever before the resin wont release and sticks solid, I get about a year from mine but I do cast a lot.

RTV silicone is my choice ... I've been using mine for 3 years now with no sign of ware on them

 

[paulm]

How do you make the moulds to fit tubes in as well?

 

[Chilprufe]

Drill a blank, glue a tube in, bung the tube leaving a little space at the end And use that blank as the original to make the silicone mold ... I'm sure there will be a video on youtube somewhere