by dahlberg » Fri Feb 20, 2015 3:11 pm
Regarding RTV and lead.
I've used mold putty, quick set, and plat 55 and tried many various shapes and sizes. Even made molds with one side of mold putty and other side quick set to see the difference in how they were affected by the hot lead.
Here's my take: For pouring standard jig heads out of lead, just go buy a do-it aluminum mold.
To make a custom one, choose the Mold Putty 15 minute. Also, when ever possible I choose to make "open" top type molds for pouring lead. They have no seams and there's never any issues with the lead cooling unevenly or prematurely in the pour hole. Just be sure you make a slot for the hook eye. You may also have to jerry rig a way to keep the hook centered perfectly.
When making lead insert "slabs" or shapes that don't lend themselves to a one part open mold, I use mold putty and might mold wood or metal backs into each side of the mold so I don't have to juggle them (or try to find them) when clamping the mold prior to pouring. Over all the putty, meaning the the 15 min version is my overall choice for molds I intend to pour lead or pewter into.
Also, for several reasons I avoid larger objects that take over 6-8 ounces or lead.But if I do I'd always do an open mold and be really, really careful about it in regards to balance.
also, I like a minimum of 3/8 to 1/2 wall thickness on the mold.
In terms of longevity, I have a couple that have produced hundreds of pours, and others that after a few dozen eventually crack from having to muscle the part out of a tight spot. Usually a crack just results in a little extra flash to trim off. Mike sent me some silicone oil that seems to revitalize the "lead" molds if they begin to feel dry. Not sure if it's actually extended the life, have to run that past mike.
good luck, be safe, only heat the lead as hot as it need to be heated,
L
Larry Dahlberg
The Hunt For Big Fish