OCFish Posted April 27, 2011 Report Share Posted April 27, 2011 I thought I read about this somewhere before, but I am having trouble with the Search function not going back very far when I search different topics. This just started happening a few days ago to me... Anyways, I poured an RTV mold, but I mis-calculated the amount I needed to completely cover the entire master. Their is a very small amount that did not get fully submerged. I need to cover this as well as have a little extra for padding. Probably about another 1/2 inch in the mold. My question is will new RTV poured onto an existing, already cured RTV mold adhere and bond? Or am I just screwed and have to start over? Any help is much appreciated....RTV is not cheap.. Thanks, Brandon Quote Link to comment Share on other sites More sharing options...
dlaery Posted April 27, 2011 Report Share Posted April 27, 2011 It should stick. don't put anything on the cured rubber. Just mix another batch and pour over it. Probably the sooner the better. Quote Link to comment Share on other sites More sharing options...
Smallie Posted April 28, 2011 Report Share Posted April 28, 2011 Everything I have read says the only thing that sticks to silicone (RTV) is silicone. My experience is limited but I have made a few molds by applying silicone to an existing mold. I have also made a RTV mold from a used bait and used silicone to smooth defects in the cavity. I would expect that you could fill air bubbles as well if you needed to. Quote Link to comment Share on other sites More sharing options...
OCFish Posted April 29, 2011 Author Report Share Posted April 29, 2011 Thank you for the replys. I am giving it a shot this weekend.. Much appreciated, Brandon Quote Link to comment Share on other sites More sharing options...
rixon529 Posted April 30, 2011 Report Share Posted April 30, 2011 RTV is not cheap.. As Smallie mentioned - the only thing silicone will stick to is silicone. You may want to consider something that another TU member (I believe it was Husky) brought up some time back... Why not reduce the volume of costly RTV needed to produce a mold by using an inexpensive filler? To use as filler in your "good" RTV: Get a couple of tubes of inexpensive (aka cheap) silicone caulking at Wallyworld (or wherever). Its usually only a couple/3 bucks per tube. Squirt the cheap stuff out of the tube and let it cure. Cut it into pieces best suited to the size of the mold you're making. Being silicon, the cheap-o stuff will adhere to the good stuff. (Even if it doesn't adhere for some reason, its being encapsulated anyway.) Using this filler technique will reduce the quantity of "good" RTV needed to produce a mold. You won't save a lot on one small mold, but if you make several larger multiple cavity molds this way, you will use quite a bit less. Hope this helps. Rick Quote Link to comment Share on other sites More sharing options...
OCFish Posted May 2, 2011 Author Report Share Posted May 2, 2011 Poured the new silicone and it worked perfectly. Mold came out great... thanks guys. Rick, that is a great idea. Seems like it would work fine and stretch your good RTV further. Will definitely try this on future molds. Thanks for the great info.. Brandon Quote Link to comment Share on other sites More sharing options...
Long Lake Lures Posted May 8, 2011 Report Share Posted May 8, 2011 As Smallie mentioned - the only thing silicone will stick to is silicone. You may want to consider something that another TU member (I believe it was Husky) brought up some time back... Why not reduce the volume of costly RTV needed to produce a mold by using an inexpensive filler? To use as filler in your "good" RTV: Get a couple of tubes of inexpensive (aka cheap) silicone caulking at Wallyworld (or wherever). Its usually only a couple/3 bucks per tube. Squirt the cheap stuff out of the tube and let it cure. Cut it into pieces best suited to the size of the mold you're making. Being silicon, the cheap-o stuff will adhere to the good stuff. (Even if it doesn't adhere for some reason, its being encapsulated anyway.) Using this filler technique will reduce the quantity of "good" RTV needed to produce a mold. You won't save a lot on one small mold, but if you make several larger multiple cavity molds this way, you will use quite a bit less. Hope this helps. Rick Rick, That is a great reminder to help save money! BTW - I also use the scraps left over in the mixing cups and trimmings from previous molds (cut up into small cubes and such)as filler- as long as the uncured silicone has already contacted the master, there is no impact to the resulting mold. Hope this helps, Dave Quote Link to comment Share on other sites More sharing options...
