anselmo Posted July 13, 2009 Report Share Posted July 13, 2009 Hi everyone Firstly I'd like to say thanks for everyone whos posted I poured my first SPs last week mainly thanks to this site and the excellent advice on it I'm planning on making a basic RTV mold of a simple fluke style lure for one shot pouring (one sided mold) I have 4 hard masters styled and ready to go I have the "pouring box" around them and the RTV ordered and on its way How do you work out how much RTV to mix? I noted some suggested that 20gms = cubic inch which is fine - I can work off that basis but the inevitable query - if I don't mix enough, can I mix another batch and add it on top without sacrificing the integrity of the mold? Thanks in advance Nick in Ireland Quote Link to comment Share on other sites More sharing options...
Husky Posted July 13, 2009 Report Share Posted July 13, 2009 Hi everyoneFirstly I'd like to say thanks for everyone whos posted I poured my first SPs last week mainly thanks to this site and the excellent advice on it I'm planning on making a basic RTV mold of a simple fluke style lure for one shot pouring (one sided mold) I have 4 hard masters styled and ready to go I have the "pouring box" around them and the RTV ordered and on its way How do you work out how much RTV to mix? I noted some suggested that 20gms = cubic inch which is fine - I can work off that basis but the inevitable query - if I don't mix enough, can I mix another batch and add it on top without sacrificing the integrity of the mold? Thanks in advance Nick in Ireland Yes you can pour on top of already poured Silicone, Nick. With that said, if you do the math right, allowing the 20 gms per cu inch, you should have more than enough. To cut costs, Don't over build the mold. 1/4" over the high point of the model should suffice. Just be sure to store them on a flat surfaces. Quote Link to comment Share on other sites More sharing options...
anselmo Posted July 13, 2009 Author Report Share Posted July 13, 2009 Perfect thanks! I suppose as well the master will displace some of the RTV as well which should be enough of an error margin Nick Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted July 13, 2009 Report Share Posted July 13, 2009 Nick, welcome to TU. 20 grams per cubic inch is about right. You could probably add more if you did not mix enough, provided you did it straight away. But why would you need to? You can easily measure the volume of your mold and mix the exact weight of RTV that you require. Read the instructions on your RTV container. Usually they quote by volume for mix ratio's, but may quote the weight ratio's also, but you may have to search (I am assuming a two component RTV). My point is that the two components will have different densities and accordingly a different ratio by weight. RTV's from personal experience can be a little fussy about ratio's and thorough mixing. I mix mine in a clear plastic cup. This allows me to view the mixing progress at the bottom of the cup, especially in the corners. Basically, what Husky wrote (he beat me to it), I just like to complicate things a little:) Dave Quote Link to comment Share on other sites More sharing options...
anselmo Posted July 13, 2009 Author Report Share Posted July 13, 2009 Thanks Dave A clear plastic cup was what I was going to use as well ("borrowing" them form work today in fact!) Nick Quote Link to comment Share on other sites More sharing options...
longhorn Posted July 13, 2009 Report Share Posted July 13, 2009 Here's the Oomoo calculator you can use as a comparison if you wish. OOMOO Quote Link to comment Share on other sites More sharing options...
