Voids in my dots......

[Silly Rabbit]

Hi everyone,
I have my first issue with casting that I figured I would do some consulting. I have been trying to make a polkadot wine stopper blank and was a moderate success. The point of failure came from a few voids in the dots.

My process was to drill a center hole completely through a 3 inch blank, then drill side holes in the blank deep enough to meet the center hole. I put the blank into my pvc mold with a cap on one end (same mold my blank came from) and then poured a second pour of PR into the center hole from the top. As it filled up from the bottom it filled each hole on the way to the top. I vibrated the bejeesus out of it and let it cure. A couple days later I turned it and sanded etc as I would normally do. I didn't do much of a shape, just turned it round and rounded the edges as this was a test.

Thanks guys

I would say it had about a 90% success rate with filling up each dot, a few of the dots had voids in it which is what I am concerned about. Any help on getting these out? I do not have a pressure pot or a compressor for that matter. I would like to avoid this purchase if at all possible as I might be buying a house in the next few weeks.

 

[ed4copies]

Without a pressure pot, I would try vibrating it AS I ADDED the resin, in hopes of it leveling and not leaving voids. Be particularly slow (in pouring) when one of your "arms" is nearly full as this is when the air is most likely to become trapped. The vibration should help clear this.

 

[erebus]

Would you mind if the polka dots are just slightly oblong? If not try drilling the holes to the center at a slight angle. The angle should help reduce bubble formation from the pour, as it pushes the air out as the area is filled, it should also let the bubbles slip free of the blank easier when vibrating

 

[skiprat]

LOL, pretend you are pouring a pint of beer and don't want a big head on it, tilt the 'glass' and leave it tilted while you vibrate and let it settle:biggrin:

 

[PTownSubbie]

You can also slightly turn down the blank before the second pour. This will allow air to escape both sides of the newly drilled holes.

I think you likely poured too fast and trapped the air in the hole with no place on the outside to escape due to the tight fit inside the mold.

Just my $0.02

 

[dennisg]

I think that if you used a slightly larger mold for the second pour you could solve this problem. Trapped air wouldn't be an issue. Or you could turn the original blank down a little to leave room on the sides in the original mold. Then turn off the second color when you shape your stopper.

 

[Smokey7385]

If you could find some small PR beads (or make them) you could then cast them in the blank. The resulting dots would be randomly spaced which may not be the look you are after though.