capt mike Posted February 26, 2013 Report Share Posted February 26, 2013 I tried to mold a soft plastic swimbait with Mold Star 15 last night. This morning the mold was cured and firm as usual, but against the plastic bait, it was gooey. Tossed the mold (about 15bucks down the drain). What the heck happened? This is my umpteenth silicone mold and I have never had a problem before. Although, this was my first RTV mold of a soft bait. Did I miss something. Or is there a soft plastic additive that reacts with RTV? Quote Link to comment Share on other sites More sharing options...
carolinamike Posted February 26, 2013 Report Share Posted February 26, 2013 There very well could have been something that reacted with the RTV. A light coating of petroleum jelly should solve that problem. Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted February 26, 2013 Report Share Posted February 26, 2013 I agree with Mike. I have done a lot of molds from soft plastics, but if it had been used, or perhaps a paint, or ........... I would not have tossed the mold away so fast. Sometimes it just takes a couple of extra days if the material reacted with something on the master. Also, sometimes if you take the catalyst and mist some extra on the gooey surface it will set it correctly. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 26, 2013 Report Share Posted February 26, 2013 If it's a two part material, you may not have mixed it completely. Quote Link to comment Share on other sites More sharing options...
capt mike Posted February 26, 2013 Author Report Share Posted February 26, 2013 It was mixed well. Just so I know i aint crazy, I used the rest of that batch of Mold Star on a clay master I made last night. Came out perfect and I pured a bait in it this AM. 7 hrs later. Now what? It aint the mold star, aint the mixing. The bait I tried to mold was a brand new soft swimbait straight out the package. I did nothing to it. Maybe that's the problem. Should I have washed it with somthing? Could it have been wearing a coating of some goop from the maker? That mold was nasty. No way I was gonna mess with it and contaminate any others. Whatever was on that soft plastic was not happy with that silicone. The rest of the mold was dry and perfect. Wherever it came into contact with that soft plastic, it was just as wet as it first went on. Quote Link to comment Share on other sites More sharing options...
capt mike Posted February 26, 2013 Author Report Share Posted February 26, 2013 By the way, I made the tail section of the clay master a little too long and the paddle tail is blowing out at slow speeds. Do you think a harder plastic would correct that? Quote Link to comment Share on other sites More sharing options...
carolinamike Posted February 26, 2013 Report Share Posted February 26, 2013 like I said, petroleum jelly. Quote Link to comment Share on other sites More sharing options...
capt mike Posted February 26, 2013 Author Report Share Posted February 26, 2013 definitely will use that Mike, but I would sure like to know what happened. Others here must have had this happen before. Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted February 26, 2013 Report Share Posted February 26, 2013 By the way, I made the tail section of the clay master a little too long and the paddle tail is blowing out at slow speeds. Do you think a harder plastic would correct that? Of course we cannot see the design, but a harder plastic might help, as well as altering the mold to beaf up the thickness just before the paddle. If you already have the mold done, then harder plastic is the easy thing to test. Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted February 26, 2013 Report Share Posted February 26, 2013 definitely will use that Mike, but I would sure like to know what happened. Others here must have had this happen before. There is really no way to know for sure. If the entire mold had soft spots, then mixing may have been it. Yours was not a mixing problem. If it was all soft and sticky, I would say your RTV settled in the container and you needed to stir it before you measured out the correct amount, but your problem did not fit that either. What I suspect is that the factory plastic had a layer of material on it that contained sulphur. OR, maybe they are learning that if they add sulphur it will give the home moder fits. RTV silicones do not set up with Sulphur, watch out for that. carolinamike gave the easiest solution to the problem that I know of. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 26, 2013 Report Share Posted February 26, 2013 (edited) Is there a chance that the swimbait was from Z-man, or Keitech, and made with the really strong, stretch plastic? I've never tried RTV with that kind of plastic. It may react badly with the silicone. I usually spray my soft masters with PAM as a release agent. I spray my hard clay masters with clear acrylic. Edited February 26, 2013 by mark poulson Quote Link to comment Share on other sites More sharing options...
RFP Posted February 28, 2013 Report Share Posted February 28, 2013 I had something similar happen about a year ago... has something to do with the type of silicone that you used...i'll see if i can dig up the actual verdict. If I recall it was something to do with the tin based silicone reacting with the mold release. use a platinum cure silicone and it wont do it. Quote Link to comment Share on other sites More sharing options...
wchilton Posted February 28, 2013 Report Share Posted February 28, 2013 Mold Star is a Platinum Cure silicone. Platinum cure silicones can be inhibited from curing by things containing sulfur, styrene, tin, other chemicals. The master was probably contaminated with something that inhibited the platinum cure. If you do a google search on "RTV silicone platinum cure vs tin cure" you'll find lots of info and may be able to narrow it down to exactly the cause. Quote Link to comment Share on other sites More sharing options...
KB Tackle Posted March 5, 2013 Report Share Posted March 5, 2013 Elaz tech, the silicone will not cure. The materials are not compatable Quote Link to comment Share on other sites More sharing options...
ROWINGADUBAY Posted March 12, 2013 Report Share Posted March 12, 2013 I had the same thing happen to a painted sculpey master I let it set for a few days and it set up ok but It had some imperfections in it from me touching it when it was sticky I think my problem was I should have left the paint on the master dry longer before molding Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted March 12, 2013 Report Share Posted March 12, 2013 I also wonder, if the master was made from recycled plastic, it probably had heat inhibitor in it. I think that Sulfur is often used in heat inhibitors. Quote Link to comment Share on other sites More sharing options...
