Help with an awkward mold

[auzorann]

I sculpted the mouth of this tongue phone a couple of weeks ago in monster clay on a vintage phone. I then molded the entire thing in rebound 40 with a plasti paste shell. On the test casting I quickly realized this mold wasn't going to work. Then I realized casting the mouth in resin and then gluing it to a phone wouldn't work either. The bottom of the phone is thicker than the mid section so I wouldn't be able to slide the mouth over a phone.

I've never worked with casting silicone but I figured it may work. I brush in the silicone on both halves of the mold, slide in the phone and close the mold. So I tried it with some alginate to see if that would even work and, to my surprise, it mostly worked. So I bought some dragon skin and made two attempts. Both failed with large air pockets on the front of the mouth. I'm assuming when I slide the phone in air is getting trapped in the cavity pushing the silicone away from the front of the mouth.

I'm adding a bunch of pictures of the sculpt, mold and some of the castings.

So I'm hoping you guys could maybe help me salvage this thing. Any help would be seriously appreciated.

 

[ultraman]

yeah there's defiantly an air issue from putting the phone into the mold.
have you tried coating both halves of the mold and then coating the phone also before putting it in?
if that doesn't work we will have to figure out a way to cut tiny air vents somehow to let the air out...of course you'll end up with more clean up dealing with the sprews leftover from the air vents...but having a good cast might be worth it!:cool

 

[trooper]

I have found that molds that have bubble issues like this, especially if it has allot of detail, though this one does not, I can put it in a vacuum chamber for a minute or two to pull the air out of the mold. once you pull the mold out of the chamber you might have to add more material. I use this mostly when making the mold, but it will work the same way when casting.

 

[auzorann]

yeah i've tried putting brushing in the silicone into both halves and then brushing in onto the phone. i still got the giant air pockets. i think it's coming from the cavity in the bottom of the phone itself. it's trapping air when i slide it into the mold. i'm thinking maybe if i drill a hole in that cavity up through the phone and vent it at the top maybe that will help.