flyrod
Member
Anyone ever tried the soft silicone molds in a vacuum / pressure pot?
silicone molds in a pressure pot?
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Ed McDonnell
Member
I've used the molds that Fred Wissen (PTownSubbie) sells under both pressure and vacuum. No problems.
Silicone molds that I made myself where I didn't degas the silicone were not happy when used under vacuum (mold distorted). Haven't used any of my own molds under pressure. When I degassed the silicone rubber, the molds I made worked fine with no problems.
Ed
Silicone molds that I made myself where I didn't degas the silicone were not happy when used under vacuum (mold distorted). Haven't used any of my own molds under pressure. When I degassed the silicone rubber, the molds I made worked fine with no problems.
Ed
bruce119
Member
I have used silicone others and my own under pressure not vacuum.
I can tell you if you go over 15-25 psi your molds will get squeezed and deform a bit. For instance the molds with the plugs that hold the tubes in place and seals them at the same time. They if you go over about 25 psi will squeeze to the point that the tube will cut into the molds wall causing the plug to tear out in short order and leave your blank looking like the resin shrinked back from the tube's end.
I made my own molds If I use pressure with them I don't go over 20 psi. If I have a need for higher pressure I use a hard delrin or PVC mold.
If you make your own try to plan ahead. If you plan on making molds that you be putting under higher pressure. I would suggest a harder silicone they make them in different hardness there are pros and cons. The softer silicone will be more flexible, easier to work, with last longer, but will distort more under pressure. A harder silicone will be stiffer, harder to work with not as flexible more pron to tearing but will handle a little more pressure.
One last note if you make your own. When you mix your silicone be sure to get as much air out as you can. This is very important if you plan to use pressure. Any air left in the silicone will shrink and cause your mold to distort expediently. When I mix the silicone put it under vacuum before you pore that will make the air expand and rise. Leave it under vacuum for about 5 minutes make sure your container has at least 3/4 of the total volume unused for the silicone to rise. The silicone will rise about 4x's it's current volume under vacuum plan on it.
Read, think, ask, trial & error, exsperament...
Good luck, Have fun
pensbydesign
Member
for most pressure pot being used around here shouldn't be used over 15psi to stay safe so they will work just fine. never had any problems with my resin savers. easy to demold being soft and flexible.
bruce119
Member
This is true but there are some situations that may require a higher pressure. About the only thing I do now that requires higher pressure is worthless wood or shredded money and the above style mold wouldn't work because you don't cast with the tube.
My point was IF you were to use the above style mold above 20-25 psi you most likely will cut into the side of the mold around the plugs. I cast my W.W. & Shred Money at 50 psi the above molds will not handle that pressure. So all depends what you do.
Most important have fun.
BSea
Member
I also used molds from Fred Wissen. I used them up to about 60 pounds of pressure without any problems or deforming. The ones I've used were the 6 vertical cast molds.
This to has been my experience. 15psi is worthless for WW, you have to force the resin into small pockets and fissures in the wood. I have had resin pushed into tube voids on Resin Savers under pressure once or twice. It was a small amount and didn't effect the casting.
PTownSubbie
Member
I just want to make sure we are not mixing apples and oranges here...
There are two different types of molds that could be being discussed here. First is the Resin Saver and the second is the "Tube-In" molds. Try not to mix the two of them up. They are not the same. The means of holding the tube in the mold is quite different.
I can speak from experience that I frequently cast with my "Tube-In" molds with a pressure of 45# - 55#. I have experienced no adverse affects of deformation on the casting. Does it deform? Maybe....but not enough to affect the casting. Can you get leakage? Only if you don't properly seat the plugs. Have I tested them to 75#? Yes. Did they hold? Yes.
I hope that helps. If anyone has any other questions about the "Tube-In" molds, send me a PM and I can answer it.
There are two different types of molds that could be being discussed here. First is the Resin Saver and the second is the "Tube-In" molds. Try not to mix the two of them up. They are not the same. The means of holding the tube in the mold is quite different.
I can speak from experience that I frequently cast with my "Tube-In" molds with a pressure of 45# - 55#. I have experienced no adverse affects of deformation on the casting. Does it deform? Maybe....but not enough to affect the casting. Can you get leakage? Only if you don't properly seat the plugs. Have I tested them to 75#? Yes. Did they hold? Yes.
I hope that helps. If anyone has any other questions about the "Tube-In" molds, send me a PM and I can answer it.
sbell111
Member
I assume that the 'tube in' molds that Fred is referring to are the ones where you have holes in the side of the molds through which you insert rupper stoppers into the tubes. These molds work far better under pressure than 'resin saver' molds simply because the stoppers are so much harder than the silicone that the resin savers are made from. A bonus is that if a stopper gets cut, you toss it and use a new stopper, rather than chunking the mold.
Both types of molds have their use, of course.
Both types of molds have their use, of course.
flyrod
Member
Thanks y'all for the feedback
I appreciate all the feedback! I've used fairly stiff silicon for making molds of decorative plaster in our 1891 victorian home restoration. I'd love to use it if at all possible.
I'm thinking of using 7/8 blanks as the "positives" for the molds, using the bottom of an empty paint can as the mold.
I've got a really cool piece of burled walnut with holes in the middle of and between the burls...think it would be a really cool worthless wood pen blank and wouldn't want to screw it up. Of course I'll try some really worthless wood before the walnut.
I'll post the results.
I appreciate all the feedback! I've used fairly stiff silicon for making molds of decorative plaster in our 1891 victorian home restoration. I'd love to use it if at all possible.
I'm thinking of using 7/8 blanks as the "positives" for the molds, using the bottom of an empty paint can as the mold.
I've got a really cool piece of burled walnut with holes in the middle of and between the burls...think it would be a really cool worthless wood pen blank and wouldn't want to screw it up. Of course I'll try some really worthless wood before the walnut.
I'll post the results.
bruce119
Member
Just one more tip. If your making a 7/8 mold I would suggest making it 1" deep. I hate filling rite to the top a PIA to handle. I actually scribed a mark just above 7/8 on my positive showing my fill point. But then again when I get going I do a lot.
Have fun
jbswearingen
Member
Brilliant! I want to make some molds but didn't want to build the box for them. I'll have to make sure my paint cans will fit into the pressure pot and make some!
I use silicone molds in my pressure pot and have had no problems. I don't know how the supplier made them, though, whether they were cast with both vacuum, pressure, or both.