Perhaps, you are using too low temperature on your oven when casting
with the centrifuge.You did not mention what type of pieces you are
having problems with. If they are somewhat thinner items, then 800 oF
is too low and the items will not fill properly… try increasing
your flask temp for the items that are not filling … increase 100 of
at a time until they fill properly. Another problem you could have
with filling is if you are not balancing the arm and flask so that you
have a perfectly smooth spin.
Pitting in silver can be caused by having too cold a flask as well as
too hot a flask depending on the items being cast… however, a no
fill situation usualy points to something being to cold and if your
metal is bright, shiny and moving around in the crucible, then I
suggest increasing the flask temp. If your metal is sluggish, then
increase your metal temp.
If the item is somewhat heavy and you are getting pitting, then lower
your metal temp or your flask temp.
For future it would be very helpful if you describe what
type of items you are having problems with… what the individual
item weight is… if it has thick / thin areas…and where the sprue
is located in relationship to where the porosity is.
Hope this will help you determine your problem. if not, then you can
email me at dan@racecarjewelry.com and I will try to help further
or call me at 401-461-7803 after 9 am eastern standard time .
Daniel Grandi
We do casting, finishing, in gold,silver,brass/bronze and pewter for the
trade