| John the OFM | 25 Nov 2012 7:58 p.m. PST |
I know that good silicone rubber molds for metal do not need or use mold release. I also know that steel injection molds do not use mold release. So, what process DOES use the nasty "mold release" chemicals, which we must remove with that witch's brew of other chemicals, so we can paint it? |
| captain canada | 25 Nov 2012 8:11 p.m. PST |
Any process could use a release. Silicone rubber lasts longer when it quickly releases. Just use a detergent.
KAM
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| MAD MIKE | 25 Nov 2012 8:43 p.m. PST |
Although moulding can be done without a release agent it is my understanding that it is used in almost every application. I know that all the 1/72 plastics I have bought have either a slight oily film or the residue of a dry spray release agent. I usually clean by soaking in Fantastik cleaner then washing with dish soap. |
| Pythagoras | 25 Nov 2012 10:46 p.m. PST |
I worked in a place that cast zinc in steel molds, plastic in brass molds, pewter and lead in rubber molds. In each of these we used a spray mold release as well as bees-wax, although the rubber molds we only used the spray to make the molds. Otherwise, we just used some talc on the rubber molds to help the metal flow better. The only other mold process we done was lost wax investment to cast brass. That process did not use a release agent because the molds were temporary. |
| IUsedToBeSomeone | 26 Nov 2012 2:40 a.m. PST |
We use Talc as a mould release for metal casting with silicon moulds. Mike |
| shaun from s and s models | 26 Nov 2012 2:48 a.m. PST |
we use a silcone spray release agent |
| GarrisonMiniatures | 26 Nov 2012 7:02 a.m. PST |
I use talc – it reduces cavitation. |
| T Meier | 26 Nov 2012 7:21 a.m. PST |
I use talc – it reduces cavitation. Yes, the particles of talc break the metal surface tension. Cornstarch also works and is less toxic, talc irritates the lungs. You have to be sure it's dry though or water in either material can steam and cause pitting. Bake it in an oven. |
| Waco Joe | 26 Nov 2012 12:06 p.m. PST |
I use talc – it reduces cavitation as well as chafing 
sorry, could not resist |
| bsrlee | 26 Nov 2012 8:17 p.m. PST |
For silicon molds release agent is not really needed for production runs of resin castings under 100 pieces these days – improvements in formulation of the RTV making it resistant to the byproducts of the resin curing. Depending on exactly what rubber & resin you are using you may get more or less castings before the mold breaks down. Of course, you still have to rely on your suppliers giving you the right stuff – IIRC Old Glory had a batch of buildings where the supplier had changed the resin chemistry & didn't tell them – the resin never went fully hard, it was always a bit soft & flexible. If you use polyurethane molds you definitely need a release agent – generally speaking they are a bit less flexible than RTV rubber but seem to be more durable with resin castings (you can still wreck them by neglect) |
| Kyn ell | 01 Jan 2013 10:00 p.m. PST |
When I used to Vac form stuff, we used to go through loads of release agent, WD40 etc. Especially if you were forming stuff with added plasticene details on the moulds (you could do it once or twice that way, but the big heating elements on the machine tended to melt it, so you had to make a resin or stone plaster form from the best vac form cast if you wanted anymore after that)
The most unusual release agent we did use just as much was a large rubber mallet, this was for hitting the forms from the wooden moulds that got stuck!
It was quite an orky thing to do really, but good fun! |
