mark poulson Posted May 26, 2016 Report Share Posted May 26, 2016 (edited) Today, I reheated some plastisol in a NorPro silicone cup, to pour some senkos. When I opened the microwave door, there was some smoke, and I found a spot on the side of the cup had charred. I had added both blasting sand and salt to the plastic, and had pour it before with no problems. I'm wondering what might have caused the charring. When I peeled the plastic out of the cup, I found two places on the bottom where the blasting sand seemed to have clumped, and melted into the silicone. Anyone have a clue what might be going on? Edited May 26, 2016 by mark poulson Quote Link to comment Share on other sites More sharing options...
toadfrog Posted May 26, 2016 Report Share Posted May 26, 2016 All sand contains minute iron oxide particles and other conductive minerals . You just happened to get that one in a thousand grains that had enough gathered into a conductive unit . Might aught to try glass beads used for fine sand blasting . 1 Quote Link to comment Share on other sites More sharing options...
mark poulson Posted May 26, 2016 Author Report Share Posted May 26, 2016 I was using the sand blasting compound from Harbor Freight. Maybe I need to pass a magnet through it before I use it again. Quote Link to comment Share on other sites More sharing options...
toadfrog Posted May 26, 2016 Report Share Posted May 26, 2016 That might help . I think though it is more of a matter of refraction of the nuke waves of the metalic particles . Micro's are tricky critters. 1 Quote Link to comment Share on other sites More sharing options...
mark poulson Posted May 27, 2016 Author Report Share Posted May 27, 2016 Well, this is the very first time this has happened to me, so I just threw away the rest of that batch of plastic, just in case it was contaminated by something. I will stir more when I have some of the blast sand added, to keep it in suspension and away from the sides and bottom of the silicone cup. I just put the finishing touches on a 3 cavity 7" senko mold, and I'm going to pour it tomorrow in watermelon/red and black flake. To achieve the same weight as the original, but to keep it more durable, I plan to use a 4/1/1 ratio of BJ's soft plastisol to sand and fine salt. I'll add a little heat stabilizer, and I'm going to try to hand pour it with my plastic at 325, to avoid dents. Fingers crossed! 1 Quote Link to comment Share on other sites More sharing options...
JRammit Posted May 27, 2016 Report Share Posted May 27, 2016 I saw the title of this thread and it reminded me to remind everyone to unplug their microwave when not in use I keep my anchor cups in my microwave, usually with leftover plastisol still in them... Its a "safe", dust free environment Well.... One day i was carving something or another.. dremel screaming, shop vac going, head phones playing.. A jumbo jet could have landed on my porch and i wouldnt have heard it I started to smell something burning, wondered, is the wife cooking??... I ignored the smell and continued about my business.... The smell kept getting stronger, and i could tell it definitely wasn't pinto beans.... So i turned everything off and heard the microwave going.... It sits in a little shelf i made right at knee level.... Some how my knee managed to mash time/10:00/start I opened the door to reveal a cloud of black smoke and an anchor cup half full of charred plastic.... Took almost 2 weeks to get that smell out of my hallway (this was before i got my shop) Probably could have been worse, could have hit 60:00!.... I keep it unplugged now 1 Quote Link to comment Share on other sites More sharing options...
tompowers535 Posted May 27, 2016 Report Share Posted May 27, 2016 Just don't tell your wife you compared her cooking to burnt plastic. LOL 2 Quote Link to comment Share on other sites More sharing options...
