Hi David, Hmmm. I wonder if there was an air bubble of some size
under the canvas sling? That bubble of air, if big enough, would
heat up and force up the sling-full of metal in a big hurry. I
had this blow-out thing happen to me once when poring 20g of fine
silver: In my case the sling was supported by a open-bottomed
tincan (a biggish can) but I hadn’t cut any ‘legs’ on the bottom
of the can. I think the legs would’ve helped reduce the blow-out
effect of any air-bubble there, as there would be an escape
route between the legs.
The result was no injury though a significant rise in the
heart rate. The metal appearred to disintergrate leaving a fine
dust all about the hearth. Having gone over the cast the only
factors that could have been a cause that were different from
earlier casts were
Also in my case the blow-out resulted in no injury - the metal
was cooled by the water immediately it blew apart into little
droplets on the ceiling etc. Quite a shock, though.
a. a contamination of the alloy.
What do you mean by this? What contamination and what might it
have done to the pour?
b. a change in pouring temperature lower than the first two
pours of the day
What is your usual way to gauge the temperature of the melt at
B r i a n A d a m J e w e l l e r y E y e w e a r
@Brian_Adam1 ph/fx +64 9 817 6816 NEW ZEALAND
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