Making My Brother’s Wedding Rings 5: Casting Part 2

So last night we made the moulds (see Part one of the casting blog for that).   Tonight we’re liquefying gold and turning it into rings.

If we’ve done a good job at the spruing, investment, and kiln drying; this is the fun and easy part.

First steps; prep the equipment.

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We’re using a centrifugal casting set up, which consists of a large drum (to protect you if your flask explodes with hot metal inside), a crucible (where the metal gets melted down), a cradle for your casting flask or your mould, and a spinning arm which gets wound up like a top, and has a brake put on until you’re ready to go.

Heating the crucible
Heating the crucible

We heat the crucible first, to help lower the time it will take the melt the metal.  Once it’s piping hot, the flask is removed from the kiln, wired into the cradle, and the crucible and flask are pushed together.

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Removing the casting flask from the kiln
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Wiring the hot flask to the arm.

More heat is applied to make sure everything is warm, and the metal will flow freely.

Then it’s time to add the gold (good bye old unworn gold, hello new, shiny wedding rings!).

The collected gold, about to become shiny and new.
The collected gold, about to become shiny and new.

It’s all piled in and heated until it’s 100% liquid; Teacher Trevor checks the molten goodness for lumps of unmelted metal, which could not only wreck your pour, but could also cause the flask to explode.  (Thank goodness for that drum!).

FIRE!! (in the crucible)
FIRE!! (in the crucible)

Once Trevor is satisfied everything is a go, he releases the brake and centrifugal force takes over; sucking the gold deep into the flask so it fills everything.

Brakes OFF; the arm spins around, using centrifugal force to pull the metal in.
Brakes OFF; the arm spins around, using centrifugal force to pull the metal in.

The arm spins for a couple minutes, then the flask is left to cool off a bit before quenching it in water.

Gold peeking out the top of the "funnel" part of the casting flask.  Cooling before quenching.
Gold peeking out the top of the “funnel” part of the casting flask. Cooling before quenching.
Quenching the flask in water.
Quenching the flask in water.

The water begins dissolving the investment almost immediately and it crumbles out of the flask.  We hear a soft ‘plunk’ as the gold rings fall out and hit the bottom of the quench bucket.  Trevor fishes them out and….  Boy, do they look rough still!

Still a bit chalky from the investment...
Still a bit chalky from the investment…
Cleaned up but still not pretty & shiny...

So what’s a sister to do?  Part 6 (and final part): Finishing.

Ready for the FINAL step: finishing.
Ready for the FINAL step: finishing.

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