Quick question on silicone molds

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Timmythekid

Sr Member
Starting to dig into my Hero Falcon now, and have used one of those cheapie silicone mold kits from Michaels to cast up one of the engine vents off the BMF. I've now got what looks like a decent mold, and am itching to start making replacement vents. Thing is, I don't have access to a store to buy casting resin, so I'm trying to work out an alternative. Anyone know if 1) I can use the resin that comes with fiberglass kits to pour these? If not, any other household suggestions that won't destroy the silicone? Also, since this info isn't in the limited instructions, 2) on a silicone mold, do I need some kind of mold release agent and 3) since I need to make at least 7 of these (6 vents, and the two smaller vents on the top of each docking arm), what's the best way to keep the mold in reasonable shape as long as possible? Thanks!!!
 

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robn1

Master Member
Is there a Hobby Lobby near you? If so you can get Alumilite resin there. If not fiberglass resin may work. It's not very strong by itself but should be fine for a detail part. Epoxy would also work. These are both heavier bodied than casting resin so you may have to brush it into the mold to get it into the details.

For mold release I've been using dry lubricant with Teflon and it works great. I'm using Liquid Wrench but there are other brands.
 

swgeek

Sr Member
There's a lot of places online to get urethane resin kits. Also, you shouldn't need any release for most rigid materials cast out of a silicone mold.
 

MonsieurTox

Master Member
Try smooth-on or look at eBay, you may find some resin. G-26 or G-27 are not my fav but they will do the job for what you want to do.
Like John said, no need for released agent, your part is not a complex shape and the original part was made out of a steel mold, you will have no problem to remove the part from your silicone mold and you won't have tears.
 

Timmythekid

Sr Member
Thanks guys! Nope, I'm in the middle of nowhere - even the trip to Michaels was while I was away on business. Wasn't looking forward to fleabay as I don't wanna wait any longer! I DID stumble onto a find though - the one and only hobby shop within 2 hours had a single, lonely, not-sure-how-long-it's-been-there 32oz Alumilite kit of some description....at sixty bucks. Ouch, but beggars can't be choosers I suppose. Anyways, locked and loaded!
 

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opal1970

Well-Known Member
If that is the case, then I would really do a bit of research in Ebay. If you plan on doing alot of work with it, you can order a larger container which is generally cheaper (price per oz.) the larger the unit. You will also have a much better variety to choose from. I like to use resins that have a high viscosity (how liquid they are), that is good for making sure it gets into all the fine detail. And you also need to make sure that the time to cure is long enough to do what you want before the resin starts to cure... i.e. you want to be able to pour it into your mold before the curing process starts kicking in. The room temperature you are working in can GREATLY influence this... if you are pouring resin in summer in a warm room, your cure time can be reduced by half or more.... working in the cold does just the opposite.

there are also resins with different mix ratios, I tend to like the ones that are 50% part A and 50% part B, just because it saves me the headaches of calculating how much of one or the other I need.

As mentioned above, you likely do not need any release agent. If I do decide that I need something, I use simple Talcum Powder. It is easy to use and very cheap (as long as you do not buy a Hobbystore version of it), what more can a guy ask for? :) I use a paint brush like the ones that come with the water color kits and dip it into the Talcum Powder and then just work it into all the detail and corners, repeating as necessary and then blowing out the access (you do not want any clumps left in the mold). The Talcum does two things for you, it is a release agent, but even better, as it leaves a dry powdery layer on the silicone, it breaks the surface tension of the resin and literally pulls it into the cracks and crannies.
 
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