Walking Dead Chess Men

Today I poured 3 cylinders of brass to make 12 chess pieces. 8 pawns and 4 rooks. It was a total failure.

A model engineering friend had donated 3.3kg of brass, in the form of spent cartridges.

First a wash in hot strong detergent..
Meanwhile the cylinders were going through drying and baking cycles
and approximately an hour before the cylinders were finished, the cartridges were melted at 1070Âșc….that is hot!
then poured. All straightforward so far. The egg yolk in the middle is actually hot fluorescent orange as in the previous picture.
but after removing the investment medium, the brass figures are disappointing. Poor surface detail. Left over brass melt ingots in the background.
… lots of surface bubbles, and voids. They do remind me of walking dead zombies.
and the rooks are similarly disappointing, with poor surface detail, voids and bubbles.

This is the first pour which I have done in 3-4 months. It was ambitious, requiring 3.25kg of investment powder, and 3 large cylinders. But these pieces will all be redone, with new 3D prints, and recasting. The failed pieces will be remelted.

I think that the main problem was that the investment mixture which I painted onto the prints was too thick, and did not penetrate all of the surface features. And the painting was not adequately thorough, leaving bare areas which predisposed to bubbles.

And the main bulk of the investment mixture was too thick. I did mix it a bit longer than usual because of the volume involved, and I did notice that it seemed more viscous than usual, and when vacuumed, the bubbles never really stopped coming.

The voids occurred mainly at the bottom of the cylinders, which indicates I think, a need for ventilation tubes. I had stopped using those for bronze pours, but maybe for brass they are necessary.

So, at this moment I feel that it was a wasted day. But I have learned some things, and have a plan for the next pours.

And I was very satisfied with the quality of the brass from the cartridges. Hopefully that will continue as a source.