hybrid RTV/Silicone mold
35 replies to this topic
Posted 15 October 2007 - 02:59 PM
any one have experience w. finepoints and tricks to get this to work? I would like to attempt using an expensive RTV grade(catalyst) silicone for a skin coat followed by a cheep "run of the mill" calking silcone(1$ grade! ha ha). i have seen some interesting threads in the past, but am still i tad unclear on exactly how this would be preformed. Q:would any cheep tube of silicone work? Q: how long do i wait after applying RTV GRade silcone before i apply the filler silicone, or does that not matter. i am allitle concerned that the filler might not adhear well to the skin layer. oh and for the sake of arguement the final goal would be a foam hardbait(lure) casting. also trying to decide the best method for addressing the hanger(eye) placemnt, should i cast some space in, or cut it out with a knife or just attempt to compression hold the thru wire eyes in place.
Posted 16 October 2007 - 09:04 AM
First, I use 100% Silicone. DAP brand is about $5 a tube, but WM ALL Purpose Silicone is $2.37.
You can cast a skim coat and lay a few beads of tube silicone (It will Adhere) after the skim cures, then fill over the cured Tube stuff OR you can lay out a bunch of beads, let them cure then lay them on the cured skim coat, as filler or dice them up and mix it in with some RTV.
Be advised, the tube stuff will float in the RTV.
In any event, the two are compatible, and using the tube stuff as a filler is a practical alternative to the very expensive RTV. The key is to make certain the skim coat totally encapsulates the model.
Instead of foam, you might want to try a Urethane Resin. You'll need micro Balloons to regulate it's buoyancy.
Here or Here.
Posted 16 October 2007 - 05:37 PM
Thanks for the pointers. let me get this understood. filling layer of 100%silcone is added while the skim coat is not set up or after it has compleately cured, or does it realy not matter in the timing.
also my goal is a fairly large bait. as i understand the hooker baits are foam type. i just need to get say a dozen built (hopefully in the next month before fishing is done!!)
is the urethane resin eaiser or stronger than the foam?? i supose at least the resin distorts a silcone mold less.
finaly while i have cast a fair amount of non-lure castings, i am somewhat concerned with joining lines from the two sides of the block.i am somewhat clumsy in my artistic abilities and am somewhat unsure if i can get the clay base sufficently flat enough(it has been a long long time since a made a mold).
by the way. thanks husky for the input.
Posted 16 October 2007 - 06:41 PM
That's why we're here.
Posted 17 October 2007 - 12:31 AM
Hi!The hooker baits are not made of foam!They are made of urethane resin and yes it's much stronger that foam!And no distorsion in the mold!That's what i use to make my lures,work great!!Cheers,Dan
Posted 17 October 2007 - 12:54 AM
When you make a resin body with the micro balloons, Does this method leave enough lattitude to be able to add ballast and still keep the lure afloat or is the density of the body just determined by the balloons and no further ballasting.
Posted 17 October 2007 - 04:42 AM
i'm not sure if i understood everything right but here are "my" experiences (ps: Husky gave me a lot of info's, hints and advices on this topic ).
urethane resin baits will not float (at least the urethane i'm using) without micro balloons. i use 50% micro balloons (volume) mixed in the resin http://www.tackleund...302&postcount=7 for "floaters"
i can still put on some balast or rattles to the lure to "tune" it....
urethane foam: i use it for topwater lures or for heavy lures, because i can put on a lot more balast to the lure. (hint from Husky: spray a light coat of i.e. "acrylic paint" in to the mold and you will have an instant "prime coat")
due to the expansion of the foam i think its essential to "clamp" the mold halves thight (watch out for distorsion)
i also use the "filler method" rtv+caulk-silikone for larger molds:
- skim coat rtv: let dry
- fill the "mold" with cured-caulk and/or rtv leftovers
- fill up with rtv
its working fine for me...
Posted 17 October 2007 - 06:46 AM
Thank's Dramone, you pretty much covered it.
Respect Husky, for sharing your extensive knowledge and experience.
Posted 20 October 2007 - 09:50 PM
Hey dramone!The urethane resin that i use floats!It's the smooth-on feather lite resin!And it work's nice!The prize is not cheep but the product is awesome!I realy like it a lot!
Posted 21 October 2007 - 05:31 AM
Thank everyone! last clarifining question . according to the tutorial the dap silocone must be first cured then mixed with RTV, Why not just apply directly to the skim coat and save adding more RTV???? Also why add Water to the siliicone wont this cause the mold to shrink with time(if you ever would need to go back and cast more).
Posted 21 October 2007 - 06:06 AM
the caulk needs a long time to cure (days...). if you you mix it with water it will cure much faster...the mold wont shrink if you use "cured" caulk as filler...
Posted 22 October 2007 - 06:49 AM
ok, dry the silicone(either let sit, or mix w water) out chop up, and mix w. RTV pour onto already fully dryed skim coat. is their a mix ratio for the water mixing?? im dying to pour this mold. also im thinking of trying one with the skim coat and letting the tube silicone cure on the skim.
Posted 22 October 2007 - 07:35 AM
The silicone needs 24 hours to cure and cannot be thicker than the directions on the tube say because it will not fully cure.
The silicone will only hold as much water as it needs to cure, all excess will run off. It will set in under an hour so you can pour very soon.
Posted 22 October 2007 - 04:49 PM
thats a very bizzar process. sounds amazing. i just placed 3tubes squirted out on a plastic plate to dry. also was lucky to find a few tubes of old cured silicone. one is 100% other is 100%pure silicone ruber w anti molding stuff added(not sure if that matters).im dying to get this bait molded. picked up RTV and started skim coat drying, its been going for 4hrs and is still liquidish.
ok so to do the fast cure silicone(water added) i just pour the stuff in a container add tons of water mix it up a ton. pour off excess, and should set up quicker?? i am super nervous about adding chips of silicone to my mother mold(first time, ha ha). that whole floating deal. not sure how im going to deal with the floating portion. more than likely i will have to build the mold up in layers.
once again thanks all for the comments. i plan on posting some picts when done.
Posted 22 October 2007 - 04:52 PM
oh so one last question. so no one has tried curing regular silicone(adhesive-rubber tube) over an RTV skin directly. that would be an ideal process if someone could figure out how to make that work!!
Posted 22 October 2007 - 07:09 PM
Well, get busy!
Posted 22 October 2007 - 07:12 PM
The key with that is patience. Air cure silicone takes about 24 hrs but that can be accelerated by putting it in a super humid place.
Posted 23 October 2007 - 06:50 PM
hmmmmm...im going to read between the lines on that ...thanks....well my aquarium hood is nearly a rain forest. it seems strange that being silicone seeps some kind of natural lubicant oil, that it will bond after curing!! my fingers are sore and beat up after an hour of chopping all sorts of old molds and dried sil caulking. ive got every finger and appendage crossed!! hope this works.
Posted 23 October 2007 - 06:58 PM
It sounds like you're right on target!
You probably did a bit of overkill with the chopping, but it won't hurt. The key is having the model covered with a layer of RTV. All else is Filler, regardless of what it's made from.