80HD_brain Posted September 22, 2023 Report Share Posted September 22, 2023 Hi all. I decided to try my hand at lure making a month or two ago. I made a master from bass wood. Since it was my first attempt, I wanted to make a mold of the entire lure and play with different joint types and placement. I applied several coats of rustoleum filler primer, sanding between coats. For the mold I used smooth on oomoo 30. This worked and I eventually learned enough to get one of my 12 or so attempts to glide correctly. Wanting to save time and eliminate variables, I decided to make a second mold of the separate halves. Somewhere along the way I saw that a 15A shore hardness is preferred over the 30, so I used smooth on mold star 15 slow. I also coated the (now resin) master (alumilte white) with rustoleum filler primer. Upon de-molding the silicone mold, I noticed the areas where my lure made contact with the silicone were sticky and not cured. The rest of the mold came out as intended. It’s only been an hour since then, so I’m not sure if it will cure or not. I’m fairly certain it’s cute inhibition since it’s been 20 hours since pouring the mold and only those surfaces did not cure. What do you think caused the cure inhibition? The fact that I was making a copy of a copy? The rustoleum filler primer? too much mold release spray? I repeated the mold making steps verbatim to my first mold. The only differences were types of silicone used, materiel under the rustoleum filler primer, i used a bit extra mold release the second time, and maybe the original wood master had more time to off gas the primer than my second attempt. No matter, I’m not in love with the design so I’m going to start back at square one with a blank piece of wood. Quote Link to comment Share on other sites More sharing options...
danthefisherman Posted September 22, 2023 Report Share Posted September 22, 2023 Yes, your silicone is not curing properly. Never worked with Mold Star before, but my experience has been that platinum cure silicones are especially sensitive and susceptible to cure inhibition. I’ve used a ton of Oomoo 30 without this issue, and it’s a tin cure silicone. You can spend a LOT of time and money trying to find the right combination of materials that will not react, but sometimes all it takes is letting your master cure fully. This includes giving both the resin and primer ample time to set and offgas. I like being on the safe side and letting my master dry out in the sun for a few days before molding. The same concept can apply when painting and clear coating. Good luck! Quote Link to comment Share on other sites More sharing options...
80HD_brain Posted September 22, 2023 Author Report Share Posted September 22, 2023 10 minutes ago, danthefisherman said: Yes, your silicone is not curing properly. Never worked with Mold Star before, but my experience has been that platinum cure silicones are especially sensitive and susceptible to cure inhibition. I’ve used a ton of Oomoo 30 without this issue, and it’s a tin cure silicone. You can spend a LOT of time and money trying to find the right combination of materials that will not react, but sometimes all it takes is letting your master cure fully. This includes giving both the resin and primer ample time to set and offgas. I like being on the safe side and letting my master dry out in the sun for a few days before molding. The same concept can apply when painting and clear coating. Good luck! Thank you for the well written response. I’ll return to the oomoo 30 and not rush the curing process on my next one. For now, I’ll fish the working model I have and carve a more realistic V2. Big Epp 1 Quote Link to comment Share on other sites More sharing options...
SacPig916 Posted September 24, 2023 Report Share Posted September 24, 2023 check all your topical coatings, clay and releases for sulpher or silicone. By chance, are you molding a 3d printed model? Quote Link to comment Share on other sites More sharing options...
80HD_brain Posted September 24, 2023 Author Report Share Posted September 24, 2023 Just now, SacPig916 said: check all your topical coatings, clay and releases for sulpher or silicone. By chance, are you molding a 3d printed model? My mold release is a silicone based, but no sulphur ingredients. Not a 3d printed model. My first was a wood carving and my second was a resin copy in two halves of said carving. Quote Link to comment Share on other sites More sharing options...
SacPig916 Posted September 24, 2023 Report Share Posted September 24, 2023 17 hours ago, 80HD_brain said: My mold release is a silicone based, but no sulphur ingredients. Not a 3d printed model. My first was a wood carving and my second was a resin copy in two halves of said carving. I'd give it a shot with 0 mold release, just the silicone mold to mold release. Quote Link to comment Share on other sites More sharing options...
Jinxd12 Posted September 25, 2023 Report Share Posted September 25, 2023 If your making a master mold and using platinum cured silicone DO NOT use anything Rust-Oleum products. Find an automotive clear coat in a can...not Rust-Oleum! There are other products out there that work but it's all trial and error based on your own steps taken from master to mold. You don't really need a mold release with a 2 part mold when making the "master" mold. It just adds to the possibility of cure inhibition with platinum cured silicone. If you want easy..get tin cured silicone. Pretty much works all the time every time unless you got lazy with stirring the cup. 80HD_brain 1 Quote Link to comment Share on other sites More sharing options...
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