RVT Silicone - Can you Clam Mold It ?

[the_hide]

I have some RVT silicone I purchased forever ago before using the 30+ Kilo's of hydrastone plaster instead. Id like to make some RVT silicone molds so I can pour plaster into these and work a little more from the "plaster master". Anyone know if you can just Clam mold with RVT silicone as red did in his clam mold silicone tutorial ?

[Tristan]

The_Hide - I have not done it, but I believe you can if you pour 1/2 of the mold and let cure, inserting locating pins or slats into the first half; after curing, coat everything with release agent and then pour second half... cut pour spout and have at it!

A question for you; what do you use to coat your plaster moulds? What's it's useful life?

Thanks,

Tristan

[the_hide]

Im in Australia so I used to use a devcon equivalent broken down with alchohol/spirits. However I have begun using a two part epoxy mix I found at a craft store called envirotex. It sets rock hard and is really easy to paint onto the molds. I can't tell you how long the molds last because I've never had to replace one yet. Only failure has been from non natural causes (ie I threw it at the wall in disgust). Mind you I don't use plaster of paris from a hobby store, it was to brittle. I use Hydrastone from US Gypmsum. Its significantly harder and keeps the detail very well.

Im also strictly a two part molder aswell so I'd assume that a single part mold would last longer, less stress , no clamping , no surface rubbing etc.

[redg8r]

Hi,

You might be able to make a clam mold with RTV, but theres a few concerns to look at first.

#1 you mentioned your RTV has been sitting around awhile, you might wanna test it to make sure its still good. RTV has a shelf life, usually around 6 mo. but depends on brand & how you store it.

#2 durometer. in the clam mold tutorial I use a typical household silicone. it has a high durometer/low shore value which basically makes it "thick"

most RTV's are pretty flimsy so you might wanna sink the bait a little deeper than the 1/8" I recommended in the tutorial.

The RTV wont be thick enough to support the bait, so you will need to either suspend it from above using something like a thin wire or a needle or something. I called it a clam mold because its totally encompassed by silicone.

#3 The clam mold is made from clear silicone, so you can see where you need to cut the mold to extract the original, I havnt seen many "clear" RTV's & theyre pretty pricey, So finding where to cut might be tricky.

Other moldmakers will use a method called a "glove mold" where one end is open & creates the pour hole. heres a link to a similar tutorial for more reading:

http://www.alumilite.com/howto.cfm?ID=7

On Step 4 of this tutorial the author uses a marker to make note of where he needs to cut the mold, I recomment you mark the Inside of the container so the mark will transfer onto the RTV rubber, ive done it & makes it easier to find the mark.

I used a glove mold to make my swimbaits, I stood the bait on its flat tail to make a glove mold described in the link above.

hope it works out for ya.

[finlander]

This glove method would be best for 1 color baits, right? And for pouring vertically, a horizontal bait. Could this mold be slit at the top for a horizontal shape, as long as the belly is wider thean the top? I am looking to pour two colors rather than paint them on.

[redg8r]

Sure,

Youll have to suspend the original by either haging from a pin, or propping it up from underneath using a needle or pin. That will eliminate the pour-hole on the short (vertical) side.

then cut the mold along the long (horizontal) side.

This is basically what I did in the clam mold tutorial, only difference is with using RTV the original master will want to either sink or float (im guessing) so supporting it from top or bottom should stabilize it in the RTV mix.

After extracting the bait you can fill the mold by squeezing it like you do those old vinyl "coin purses".... remember those?

the household silicone is thick enough that it will support the master in place itself.

Good luck bud, let us know what you find.

[finlander]

Thanks Red. In that last tutorial you posted, they talked of a rubber rtv. Is that a different material from the 100% pure silicon I've used, that takes forever to set when using a large amount? Anyway to cure it faster? Who makes aluminum molds and are they a superior product?

[redg8r]

Thanks Red. In that last tutorial you posted, they talked of a rubber rtv. Is that a different material from the 100% pure silicon I've used,

Yes, very. RTV is a superior molding medium. RTV is usually a pourable consistency kinda like waffle syrup in consistency

household silicone is like caulk whan catalyzed its as thick as taffy.

that takes forever to set when using a large amount? Anyway to cure it faster?

add more water & stir thouroughly.

you can also work in batches, using a layer effect. silicone will adhere to silicone even after its cured.

Who makes aluminum molds and are they a superior product?

Superior? depends on what you consider "superior" the aluminum mold life is virtually indefinite. compared to RTV but your bait detial is restricted to the mold designers CNC skills, both below are very skilled CNC wizards.

Del of "Del-mart.com" & Robert of BTS baits "bobstackleshack.com"

are the only 2 manufacturers of soft plastic aluminum molds that I know of.

we have reach an agreement with both to carry thier lines here (soon) or you can go directly to thier site.

Good luck