Mojo Posted November 26, 2004 Report Share Posted November 26, 2004 I bought some RTV for making masters from Sculpey. I'm ready to mix my first batch but I've read on some mold making websites that you should use a vacuum cabinet to remove all the bubbles from the mixing container before pouring the RTV into the mold box. Is this necessary or can i just mix gently and pour into a corner like you would with plaster, durham's, etc.? I have access to a vac pump (old freezer compressor), but I don't want to make a cabinet unless I have to. Anyone? Bueller? Thanks! Quote Link to comment Share on other sites More sharing options...
RobShaw Posted November 27, 2004 Report Share Posted November 27, 2004 Ive probably made 100 different molds from RTV Silicon without using the process you described. Of course, not every mold turned out like i had wished...but the majority did. I just wish that stuff wasnt so darn expensive! Quote Link to comment Share on other sites More sharing options...
Mojo Posted November 27, 2004 Author Report Share Posted November 27, 2004 Thanks Rob! That's what I needed to know. I built some mold boxes out of acrylic today for some prototypes. I'll mix up some RTV tomorrow and let you know how it goes. Quote Link to comment Share on other sites More sharing options...
Art Brush Posted November 28, 2004 Report Share Posted November 28, 2004 Hey Mojo, Here's a few tips that might help ya with casting silicone ... To get a glossy finish on RTV molds: Before I mix the RTV I lightly mist a few thin coats of Mann's Ease Release 800 on the model & mold box. It's not used so much as a release agent as it is a "glosser". The wax in the release agent will look hazey when you first put it on. By placing the mold box about 8 inches under a 60 watt bulb the wax will melt and make a micro sheen gloss. 15 mins under the lamp should be long enough. This is then captured & replicated in the mold when the silicone is poured. To avoid trapping air bubbles: Mix the silicone as directed and mark the time. The directions should have a "pot life" time to let you know how much time you have to get the rtv into the moldbox. I cast silicone in 3 or 4 layers without using a degasser. Number of layers depends on how tall the model is. I cast the first layer then use my air brush to blow air to pop the bubbles. Leave it stand a minute then blow some more air. By clearing the bubbles and allowing the RTV to stand, more bubbles will rise and travel further away from the models surface. Within a few mins that layer should be bubble free. Continue the process untill the moldbox is full. Makes a great mold. If you don't have an airbrush you can blow air thru straws for the first couple layers. Tight lines, Shawn Quote Link to comment Share on other sites More sharing options...
rookiepourer Posted November 28, 2004 Report Share Posted November 28, 2004 I have had the best luck by pouring the rvt over the blank that way the air bubbles rise up, which ends up being on the bottom of the mold. good luck. Mark Quote Link to comment Share on other sites More sharing options...
