bryanmc Posted April 11, 2017 Report Share Posted April 11, 2017 Has anyone had any issues with moldstar 30 not curing when poured over a plastisol master? I was trying to create a mold from a swimbait I had and after hearing so much good about moldstar 30 I thought I'd give it a try. The master was secured to a metal sheet with double sided tape and surrounded with a wooden mold box. I mixed it according to directions and poured it the same way I've poured many other brands (Alumilite quickset and high strength, SRC cast-a-mold 30 and others). After 16 hours I went to demold the master. Everywhere the moldstar 30 touched the master was totally uncured as if it had just been freshly mixed while everywhere else was completely cured. I've never had any other RTV not cure against plastisol. Has anyelse had a similar experience? I'm wondering if I got a bad batch or this is just something you can't do with moldstar 30. This is an image of the inside of the mold. I had it turned upside down after I took it out of the mold box and supported at the ends. The master just slid out after 5 minutes or so and this is the result. Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted April 11, 2017 Report Share Posted April 11, 2017 I don't know Moldstar products so I can mostly suggest you contact their customer support. I can tell you this much generic information. Silicones come in 3 basic types to the best of my knowledge. 1) Solvent/evaporation based. This is like Silicone caulk. It evaporates the solvent that keeps it liquid. It can be used to make molds but is much harder to work with and I am sure is NOT the type Moldstar 30 is. 2) Tin Cure or condensation Silicones. 3) Platinum Cure or addition Silicones Without going into a chemistry lesson here, just know that the three behave differently. Platinum cures or addition silicones can react to items on the surface, such as left over mold releases, scents, paints, etc. If that happens, then I have seen exactly what I am seeing in your picture. I can't be sure, but ................ Best to contact Moldstar directly. Until you get a response, you might try cleaning the masters very very very well. Good luck. Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted April 11, 2017 Report Share Posted April 11, 2017 Update. I checked their website and Modstar is their Platinum cure material. I am sure that it is materials on the surface of the "masters" that is causing the problem. Clean them with rubbing alcohol or at least give them a good trip through the dishwasher and maybe that will work. Oomoo or MoldMax might have been a better option for the SmoothON line for what you are doing. Maybe even their Polysulfide Rubber but I am not an expert on SmoothON products. Quote Link to comment Share on other sites More sharing options...
bryanmc Posted April 11, 2017 Author Report Share Posted April 11, 2017 I actually did contact customer support and got quite a lesson in the different types of rtv (very much like your first post thanks). I didn't realize that 1:1 rtv is generally platinum cure and 10:1 rtv is generally tin cure. Platinum cure is much more finicky as far as what it will work with. The master was clean before I started (always make sure to wipe them down with alcohol). They didn't seem surprised that the mold star wouldn't cure against plastisol although I could swear there are some who say they use it that way. All in all it was a $35 learning experience. I tried some tin cure 30 from Specialty Resin and Chemical, and although it works well, I think it really needs to be used in a vacuum chamber for best results. I've had a couple molds come out bad because a bubble got caught in just the wrong place. Seems I have the best luck with good old alumilite quick set... no air bubbles, good durability and results. The price is the only draw back (except with a Hobby Lobby coupon). Quote Link to comment Share on other sites More sharing options...
Baitjunkys Posted April 11, 2017 Report Share Posted April 11, 2017 Ive never used it on a plastisol master, Only a hard master. Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted April 11, 2017 Report Share Posted April 11, 2017 2 hours ago, bryanmc said: I actually did contact customer support and got quite a lesson in the different types of rtv (very much like your first post thanks). I didn't realize that 1:1 rtv is generally platinum cure and 10:1 rtv is generally tin cure. Platinum cure is much more finicky as far as what it will work with. The master was clean before I started (always make sure to wipe them down with alcohol). They didn't seem surprised that the mold star wouldn't cure against plastisol although I could swear there are some who say they use it that way. All in all it was a $35 learning experience. I tried some tin cure 30 from Specialty Resin and Chemical, and although it works well, I think it really needs to be used in a vacuum chamber for best results. I've had a couple molds come out bad because a bubble got caught in just the wrong place. Seems I have the best luck with good old alumilite quick set... no air bubbles, good durability and results. The price is the only draw back (except with a Hobby Lobby coupon). Don't toss out the MoldStar. I am sure that it has a place once you get hard masters made up. Most Platinum Silicones last longer in the long run. I was lost when my Hobby Lobby was out of Alumilite Quick Set and HS3. Only hobby store I have the app on my phone for. Quote Link to comment Share on other sites More sharing options...
rhallman Posted November 17, 2018 Report Share Posted November 17, 2018 Just experienced the same thing. I was making a Mold Star 30 mold to pour both plastisol and platinum silicone swimbaits. Mold came out great (original made from resin). Poured a plastisol bait, then after using ample mold release made for platinum silicone, I poured Ecoflex silicone in the same mold. Big mistake. Only the inner cured. The outer touching the mold was a total mess. I am experimenting to make sure it is not the release, but I am certain it's due to the plastisol. Platinum silicone is extremely sensitive. Just did not know it was sensitive to plastisol. Tin based like Mold Max 30 is great. Not nearly as sensitive. Thanks for bringing this up. Quote Link to comment Share on other sites More sharing options...
OIR Posted November 18, 2018 Report Share Posted November 18, 2018 some soft bait just dissolves the silicone..had a few Quote Link to comment Share on other sites More sharing options...
Darkman Posted November 18, 2018 Report Share Posted November 18, 2018 I had the same problem, it's cause you used platinum cure, you want a tin cure when your master is made of plastic, you can clean it all you want still going to have the same issue, it will work with any other master. i was making a copy of of a worm I liked and that happened, the platinum reacts badly with the plastisol, think if I remember correctly it was the sulfur. So now I use Tin cure for mold making. Live and learn 2 Quote Link to comment Share on other sites More sharing options...
Landry Posted November 22, 2018 Report Share Posted November 22, 2018 Tin cure is better for that application. And alcohol will inhibit moldstar cure too Quote Link to comment Share on other sites More sharing options...
rhallman Posted November 22, 2018 Report Share Posted November 22, 2018 Update and hard lesson learned. You cannot clean a mold that's had plastisol poured in it and then pour a platinum silicone bait. One plastisol pour bait, then cleaned with soap and hot water, then multiple acetone cleanings. No help. It's either a plastisol mold or a silicone mold. Can't be both. 1 Quote Link to comment Share on other sites More sharing options...
