Matt Moreau

Whats The Best Rtv Silicone To Make Molds? This Is My Experience....

7 posts in this topic

Howdy Guys,

I researched on here a little and didnt find too much on RTV Mold making pertaining to brands and hardnesses. I have been testing different silicones lately and was wondering what everyone else likes when making their molds.

Generally there are 2 types; Tin Cure Condensation Silicones and Platinum Cure (Addition) Silicones. I have used only Tin Cure. From my research you want a shore hardness of 8-20A... Up to 30 is workable but over that they are too hard and break down and tear much faster.

I have tried Smooth On(the Oomoo one only), Tap plastics, ViSil, Alumilite and a couple other ebay cheapies. So far I have found that the Alumilite is by far and away the best product. SmoothOn and Tap were both second as their properties were very similar. But they both started breaking down after 30 baits or so and produce a lot of bulles when mixing so a vaccuum would be a good idea for these. The other ones are worth your time and/or money. I may try a few more on Ebay to see but so far Alumilite is the king!

Pros of Alumilite High Strength 3;

It has a thin viscosity when mixed so gets in every crack and crevas capturing all the detail and undercuts

It does not have many air bubbles caused from mixing. This i believe is caused by the much thinner viscosity when mixed than other brands, thus no vaccuum needed

I havent had tearing issues yet or mold breakdown

Great release properties

Smells decent

Cons;

Cost

Please let me know what you guys have found and if I am on track here... Again this is limited research to what i have tried and I would love everyones opinions.

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Aeromarine makes a pretty good silicone as well... I've used many others and it seems to be on par with the best and costs less.

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My experience has been with Alumilite HS2 and Smooth-on 25 & 30 (tin). The Smooth-on 30 (tin-pink) is a very good rubber for 2 piece molds. Ive had more than 100 baits casted from these, and still going strong. The platinum rubber is the next step up for "library" life and accuracy over the life of the mold. But, requires vacuuming before pouring. Im in the Smooth-on camp for sure.

I like 2 pc molds even if I am making a solid one pc bait. I also preheat molds and always use release agent.

Not much durability with Oomoo, especially if youre having to pry out a casting from a one peice mold over and over again. The labor for a 2pc mold is much greater, but the reward is many many lures that are alike. I dont look at costs too hard since the price per bait goes way down if you can cast over a hundred from one mold.

Hope that helps.

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I've been using Alumilite HS2 for my molds and it works good for the big baits that I use. It captures details well and no bubbles. I wish it set faster but such is the life of a lure maker.

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the issue i had with the alumilite is the cure time, 24 hours is such a pain expecially prototyping...oomoo cures so much faster (30 is like 5 hours) and is really durable if you plan out your part undercuts. if you have a bunch of undercuts just be gentle removing the part. i can generally get 30 to 40 hard multi joint swimbaits out of a mold if im careful and take my time. also remember if you get a tear mix a little of the same silicone your mold is made of and brush a small amount on the torn pieces to "glue" them back together(if is a big enough section that was torn apart). End of the day your mold is only as good as the prep you put into it..IE venting ect.

i use the platinum cure for casting platinum cure silicone part..if you mix tin and platinum cure silicone your going to have a mess.

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from my limited experiments. the cheeper silicons dont last as long. shrink with time.locally availble dowcorning is expensive but lasts and doesn't shrink with long term storage. i have molds that have been stored now for 20years and are showing no shrinkage that i can tell!

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Aeromarine makes a pretty good silicone as well... I've used many others and it seems to be on par with the best and costs less.

Yup, I've been happy with the aeromarine. I just recently tried the transparent stuff. However, the purple stuff smells like grape soda!

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