Sprue goo casting

Hi guys,

This is where I'm up to so far with casting using sprue.

The yellow bit on the left is the bit of toy with a cheq plate patten that I'm going to try and cast, I used bluetac to fill any holes.
The black bit at the back is the tray that I used to glue the yellow bit into with wood glue, to make the mould
The Gray bit is the concrete mould, made by mixed up at 4 parts concrete to 1 part sand.




Close up of the yellow bit


Close up of the concrete mould, there is a few air bubbles, but it looks ok.


Some Sprue goo used as filler, this batch was made by just covering the sprue bits in a small paint jar,
it is too think for casting, but it was good to test how much it shrinks (not much)




This is the stuff that I will use to make the sprue goo
The jar in the middle will be half filled with sprue bits, then the priming fluid will be added to the top of the label, and left for a few days to melt
The smaller car on the right, is a old paint jar, with 1 bit of sprue in it, as a text, it fully dissolved within 24 hours, and it has the constance of water, ( too thin to cast).
But the thinner it is, the longer to dry and the more it will shrink.




When the sprue goo is ready, I will then put it into the concrete mould and leave it for at least a few days.

I'll keep you posted

-Dion

Interesting stuff Dion,

using resin would be a lot quicker and easier mate.

How do you get the part out of the concrete mould? Or is the mould single use?

I know Resin would be quicker and easer, and a lot more versatile, this stuff would only be good for flat, one sided items, with low detail, etc.

but I'm curious, and I want to see if it can be done.

I haven't though about getting it out yet, I might put something in it to grip onto to take it out, and I'm hoping the concrete will last for a few casts, if I can get it out, lol.

hope it goes ok Dion. that priming fluid is pretty much all I use for glue these days, use an old tamyia bottle for small jobs and a long glass pippet for gluing larger items and scratch building. not long threw out a big box of sprue, but may be able to gather you some for October

Thanks Mutley,

I use the Tamiya extra thin stuff if the fit is good, it doesn't smell as bad as the priming fluid, and I use the Revell contacta for the bits with a bit more of a gap.

I started to sand the stuff that I used to fill the legs on the driver, and noticed it was still a bit soft on the inside, but it dose not seam to shrink that much.

I've found that the goo forms a skin on it fairly quickly and traps the goo inside and stops it from airing out properly, just let it sit a while longer and its fine

It actually worked in my favour, because I also done the arms, and after a while insted of having to try and carve out the inside of the hand, I just used the blunt end of a toothpick, and pushed it into the shape I wanted.

I don't think this stuff would work for car bodies, but I think It will have a few uses

another way is to put in a bit of goo and then press in off cuts of sprue

What I did with the driver was to glue sprue bit in, then just fill the gaps with the putty

They is how the testing turned out.

Two things hapened, the goo ate away the concrete and stuck to it Very well


and it also created a large air bubble inside.


I also tried a thicker goo on a flat surface, but it bubbled also.

There may be a way to stop the bubbles forming, using pressure or a vacuum, but I don't have either of these that I could use. so I will forget about it for now.
-Dion