Casting????????

[JTTHECLOCKMAN]

Those of you that do casting I have a question. I am trying to cast colored resin onto a tube that has aluminum parts. I use Silmar41 as my go to resin for casting. My question is will the resin stick to the parts or will it shrink away from them??? Would using alumilite be a better choice??? Or going back to the Silmar, would it be a better idea to coat the items with resin and let cure before casting as a blank??? I use that method when doing braided blanks. But in those cases the braid is more or less encapsulated in th resin. With these blanks the aluminum will be protruding through the resin and turned away with the blank to shape and form. Thanks.

[dabbler]

I’m not familiar with Silmar41 but I regularly embed aluminium with PR. Sometimes I lightly epoxy several wavy slices of alum to the brass tube. When turned down this produces a metal wave on all sides. Sometimes I embed a single wavy slice within a PR blank for drilling. I don’t use pressure. The PR has never shrunk away from the alum, just the silicone mould.

[dai sensei]

I paint clock parts blanks with acrylic clear spray as it seems to help with boding. Then when set (24hrs min), paint with the mixed PR mixture prior to pouring in the rest of the warmed resin in the mold by trickling it in (to minimise bubbles) and leave to set (ie no pressure).

Aluminium can always cause problems with bonding, I will still follow the above method, provided no oily surface and it is not smooth

[MBUMIK]

i am guessing that you are using disks of aluminum placed along the tube or similar idea and the resin will fill the gaps between the aluminum plates

i have noticed that the resin tends to shrink away from the mold towards the center, and not really by a great deal, i would think that it should work OK

if you are making special cuts on this blank that are hard to do then i would suggest that you experiment with a couple of disks drilled, placed on the tube in a mold and pour the resin in, a basic experiment is better than loosing a masterpiece

i hope it all goes well, keep us informed as to your findings

MIK

[JTTHECLOCKMAN]

I may have to run some experiments because I am relly getting no definete answers. I will try some simple tests using both resins. The alumilite I have is quite old so hopefully it still works. I have tried this once before but in that case what I did was after the blank was cast I placed in a toaster oven to finalize the curing as I normally do. But what happened was the adhesion was not good. It was brought up to my attention that by heating I expanded the aluminum and then when it cooled it shrunk thus pulling away from the resin. This made sense but I never followed through with any further experimenting. So this time I will elliminate the heat. This cast will not be too dramtic but will challenge some. I have other ideas if I can get my ducks in a row and get a sure fire method down. Thanks for the answers.