School Master Posted March 26, 2018 Report Share Posted March 26, 2018 This is my first attempt at a lead silicone mold. Made a 2 piece bladed jig mold using Smooth-On Mold Max 60. Everything went to plan and the mold turned out really nice. I attach the blade to a link before I pour it, so no opening eyes and it's never coming off. My issue is I'm getting LOTS of gas voids all over the jig as seen. I made a spinnerbait mold as well that isn't pictured and I'm getting the same result. Any ideas? Will vents fix this? 1 Quote Link to comment Share on other sites More sharing options...
dlaery Posted March 26, 2018 Report Share Posted March 26, 2018 some talc powder might help. take a rag with some powder on it and dab each side including the gate running in the cavity, turn it upside down and tap on the mold to get ride of any small piles of powder in the cavitity, then put it togeather and pour. maybe letting set a little longer before demolding. 1 Quote Link to comment Share on other sites More sharing options...
mark poulson Posted March 26, 2018 Report Share Posted March 26, 2018 Contact Smooth On and ask them for help. 1 Quote Link to comment Share on other sites More sharing options...
School Master Posted March 26, 2018 Author Report Share Posted March 26, 2018 WOW great idea Mark, Sometimes the easiest answer is the best answer! I will also try the talc powder in the mean time Mr. Leary. Thanks guys 1 Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted March 26, 2018 Report Share Posted March 26, 2018 Did you degass your silicone when you made your mold? Venting might indeed help, but .......... I am not a Smooth-On guy, more of an Alumilite guy myself, but a lot of the things are interchangeable to a point. If they can help at Smooth-On, best to get the information straight from the horse's mouth; but, if not, then come back to us and perhaps we can work it out. 1 Quote Link to comment Share on other sites More sharing options...
School Master Posted March 26, 2018 Author Report Share Posted March 26, 2018 I did not, due to the non-degassing capabilities of my shop!! I figured it was just to remove air bubbles to avoid voids in the mold. Interesting though, I wonder if they trapped gas is causing a reaction? Totaly makes sense. Will it get better with time? 1 Quote Link to comment Share on other sites More sharing options...
OIR Posted March 26, 2018 Report Share Posted March 26, 2018 (edited) use a candle let it smoke and turn the mold black it makes release eaiser and pre-heat the mold the same time. I mix in powder chalk 20% in the silicone rubber (RTV Silicone Moulding Rubber Shore A15) Edited March 26, 2018 by OIR 1 Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted March 26, 2018 Report Share Posted March 26, 2018 3 hours ago, School Master said: I figured it was just to remove air bubbles to avoid voids in the mold. It is, and most of the time you do not need to degas silicone. In the case of lead molding, it is a little different. The hot lead causes the silicone to expand. When the silicone expands, pores/voids that were otherwise not seen or even matter, can open and create similar things. Most lead silicone molds don't last long so keep that in mind. 19 minutes ago, OIR said: use a candle let it smoke and turn the mold black it makes release eaiser and pre-heat the mold the same time Remember that hot flames are higher than silicone can take so be careful. Also, I have never found removing anything other than silicone from silicone to be difficult. Lead just drops out so I don't see this is necessary at all. 22 minutes ago, OIR said: I mix in powder chalk 20% in the silicone rubber This is new to me. OIR, what does the chalk do to the silicone rubber? Time for me to learn something new here, awesome. 4 hours ago, School Master said: I wonder if they trapped gas is causing a reaction? Not so much a reaction, but if air cannot get out, then it will create bubbles. Moisture will also do this. My concerns would be that most of the time the air would be pushed to one spot, so........ the reason I asked about degassing the silicone. 10 hours ago, School Master said: Will vents fix this This would be the first thing I would do, and it is the easiest to do. A sharp razor knife and you can cut a vent in the silicone. If it fixes it, great, if now, then it will only leave a small sprue to remove. 10 hours ago, dlaery said: some talc powder might help. take a rag with some powder on it and dab each side including the gate running in the cavity, turn it upside down and tap on the mold to get ride of any small piles of powder in the cavitity, then put it togeather and pour. This reduces the surface tension allowing the air to move out better. Without a vent, it still has not place to go, but this is also a great test to do. I have seen this work on resin as well. 1 Quote Link to comment Share on other sites More sharing options...
OIR Posted March 27, 2018 Report Share Posted March 27, 2018 (edited) 25 years ago.... I was told that chalk makes the mold more hard and +10-15% resistant to heat to the left : 25 years old lead (2 part mold to the right : 4 days old (1 part mold) Edited March 27, 2018 by OIR 1 Quote Link to comment Share on other sites More sharing options...
School Master Posted March 27, 2018 Author Report Share Posted March 27, 2018 Nice OIR, I wish I would have mixed some in mine. I hope mine lasts for 25 years! I still have a decent amount left, so maybe I will try it on my next mold. 1 Quote Link to comment Share on other sites More sharing options...
Jeff Hahn Posted March 29, 2018 Report Share Posted March 29, 2018 I had a few silicone molds made by InShore tackle Company several years ago. They recommend using talc as a release agent. They also vented every mold they made for me. 1 Quote Link to comment Share on other sites More sharing options...
jcool3 Posted April 2, 2018 Report Share Posted April 2, 2018 yes, baby powder makes all the difference. Dust the inside of the mold before each pour 1 Quote Link to comment Share on other sites More sharing options...
Saugerman Posted April 2, 2018 Report Share Posted April 2, 2018 I use the baby powder on difficult molds also, It usually helps quit a bit. It's worth a try. 1 Quote Link to comment Share on other sites More sharing options...
School Master Posted April 10, 2018 Author Report Share Posted April 10, 2018 (edited) UPDATE: The baby powder worked like magic gypsy dust!! Poured a couple of each and they came out really nice! Thanks for the tips everyone, now we will see how long it holds up. I will get a couple pictures up when I finish some Edited April 10, 2018 by School Master 1 Quote Link to comment Share on other sites More sharing options...
Jjdubbs75 Posted October 27, 2019 Report Share Posted October 27, 2019 Hey there saw this post from the op and i just made some two part molds with the same silicone and having the same issue. I am making big jigs though for vertical jigging and i havent found out what is the solution. The baby/talc helps but didnt solve it as well as made a vent and widened vent as well as made a giant sprue which ruined the mold but tested to see if the flow was restricted. Still getting voids mainly on the two ends and incomplete areas. Is there any mold making materials even silicone that are real superior for making big objects/lures besides going to a metal shop guy to make one? Trying to get this right but cannot settle with powder coating to fill in a crappy finished jig. Help would be much appreciated. Thank you!!! Quote Link to comment Share on other sites More sharing options...
