This is for Buggybuilder from a question he asked me in the pneumatics forum. This is something I put together a year or so ago and I have not checked all the links in this document to make sure they are still active. If you have more questions feel free to ask.
1. You need a some type of skull to start with like DeadSpider shows at this link
http://smg.photobucket.com/albums/v.../Halloween 2005/Prop Prep n Stuff/Misc Stuff/
I used a Bucky 2 piece skull to make molds of it worked great. I have also used the Large Plastic Skull Candle molds for both plaster and foam. The foam has to have a "mold release" I bought some in a spray can from a vendor.
2. Based on the pics the skull is covered with either RTV Rubber or clear silicone. The RTV rubber is normally a shore 30 strength. If you look at the pics the mold is being removed from the foam by turning it inside out. Here is a link to another person that made his own with RTV rubber.
http://www.halloweencreations.com/skull molds.htm
Here is another thread about silicone molds
http://users.lmi.net/~drewid/silicone_faq.html
Here is yet another link on making the molds
http://www.themonsterlab.com/skullmolding1.html
3. This is the method I use since it is much cheaper than RTV rubber
Method on using 100% silicone caulk for making the mold.
http://forums2.gardenweb.com/forums/load/hypertufa/msg1217385422593.html
4. You need to get some clay that is non hardening from the craft store I used plastica clay from Hobby Lobby so you can fill in the eye sockets and nose a little. This is used to cut down on how deep the undercuts are on the mold. The undercuts are the areas that are the most difficult to get the mold removed from the cast and the less the better.
5. Once you have the skull covered with the silicone or RTV 1/2" thick is a great thickness to get it to in layers allowing to to dry in between applications. You need to make a support shell to cover it so that when the foam expands the skull keeps its shape. It looks like DeadSpider used Plaster of Paris and some layers of cheese cloth to make it. Its made in 2 halves so its easier to remove. trust me on that one !
5. The Foam is your basic 2 part Foam A & B the Marine type is a 2LB foam
and it expands the most and is the cheapest and works fine for this application I have also used great stuff spray a little spritz it with a water and spray some more. Moisture is what sets "cures" GreatStuff Foam not Air. The results vary at each cast.
6. Mold release ? Silicone does not stick to much of anything except itself so no mold release is needed. If you have a plastic skull mold like a candle mold the Mold Release from Smoothon is a must. or else the mold is ruined by the foam forever.
I have got bit by the molding casting bug and enjoy learning new things. The Silicone molds work great even for making skulls with Plaster if you want to. I recently melted a bunch of hot glue sticks in a sauce pan and poured it into my mold and make a translucent skull it was kind of neat.
Now is it cheaper ? Well foam skulls are out there in quantity for $ 5 - $8 each and this method will come out close to the same cost when its all said and done with the cost of the 2 part foam but your mileage may vary. But you made them and its fun so why not ?
enjoy
1. You need a some type of skull to start with like DeadSpider shows at this link
http://smg.photobucket.com/albums/v.../Halloween 2005/Prop Prep n Stuff/Misc Stuff/
I used a Bucky 2 piece skull to make molds of it worked great. I have also used the Large Plastic Skull Candle molds for both plaster and foam. The foam has to have a "mold release" I bought some in a spray can from a vendor.
2. Based on the pics the skull is covered with either RTV Rubber or clear silicone. The RTV rubber is normally a shore 30 strength. If you look at the pics the mold is being removed from the foam by turning it inside out. Here is a link to another person that made his own with RTV rubber.
http://www.halloweencreations.com/skull molds.htm
Here is another thread about silicone molds
http://users.lmi.net/~drewid/silicone_faq.html
Here is yet another link on making the molds
http://www.themonsterlab.com/skullmolding1.html
3. This is the method I use since it is much cheaper than RTV rubber
Method on using 100% silicone caulk for making the mold.
http://forums2.gardenweb.com/forums/load/hypertufa/msg1217385422593.html
4. You need to get some clay that is non hardening from the craft store I used plastica clay from Hobby Lobby so you can fill in the eye sockets and nose a little. This is used to cut down on how deep the undercuts are on the mold. The undercuts are the areas that are the most difficult to get the mold removed from the cast and the less the better.
5. Once you have the skull covered with the silicone or RTV 1/2" thick is a great thickness to get it to in layers allowing to to dry in between applications. You need to make a support shell to cover it so that when the foam expands the skull keeps its shape. It looks like DeadSpider used Plaster of Paris and some layers of cheese cloth to make it. Its made in 2 halves so its easier to remove. trust me on that one !
5. The Foam is your basic 2 part Foam A & B the Marine type is a 2LB foam
and it expands the most and is the cheapest and works fine for this application I have also used great stuff spray a little spritz it with a water and spray some more. Moisture is what sets "cures" GreatStuff Foam not Air. The results vary at each cast.
6. Mold release ? Silicone does not stick to much of anything except itself so no mold release is needed. If you have a plastic skull mold like a candle mold the Mold Release from Smoothon is a must. or else the mold is ruined by the foam forever.
I have got bit by the molding casting bug and enjoy learning new things. The Silicone molds work great even for making skulls with Plaster if you want to. I recently melted a bunch of hot glue sticks in a sauce pan and poured it into my mold and make a translucent skull it was kind of neat.
Now is it cheaper ? Well foam skulls are out there in quantity for $ 5 - $8 each and this method will come out close to the same cost when its all said and done with the cost of the 2 part foam but your mileage may vary. But you made them and its fun so why not ?
enjoy