Here’s my 2 cents on spruing.
Buy the pink spru wax in 10 ga 8 ga and 6 ga. One of these three
sizes will work well for most cast pieces. Heavier for the mens
lighter for the womens and pendants. All attachments should look like
tree trunks going into the earth. Both on the piece and connecting to
the spru base. The flow of the metal will work better if there are no
sharp corners. The moten metal can breeak any sharp corners of the
plaster off. This broken off plaster can travel into your object
making it junk. Keep away from the pinched straw syndrom and sprus too
long. The length should be about 1/2 inch from the button or tree.
A note for casting temperatures. If you have a piece in production,
set up four or five flasks of exactly the same items. Now guess at the
proper temperature you think will work. Cast the first flask at that
temperature. Keep track of this flask. For the following flasks drop
the temperature 100 degrees each. Make sure the temperature stablized
at the next temperature before casting. Cast until one of the flasks
doesn’t fill. Try to get the molten metal to freeze by having the
flask too cold. Now if you add 100 degrees to the flask that failed
you have the perfect temperature to cast that item. A lot of your
porosity problems will go away. You may think this is expensive to do.
But you can do it in silver and gold temperatures are very close.
Flask temperature is critical for flow, fill and porosity.
TR the Teacher & Student