Casting problems

If your hearing a crack in the investment when you put it on the
vacum, it sounds to me that your tree was to close to the top of your
flask. (the top of your fask when you invest, the bottom when you
pour) try using a taller falsk or try shortening the length of your
tree. If it is just flashing you are experiencing try using less water
or make sure your water isn’treally cold. You can use warm water to
invest but it sets up much quicker.

I have been having a casting problem. There is a crust that forms on
the casting and button. It is a medium gray color as opposed to the
white on the investment and always has a discoloration and porosity
underneath. It is very hard and must be chipped or scraped off. It
forms around the edge of the button in most cases but also extends
on spots to the rest of the casting. It seems to be mostly on the
bottom half of the casting. I am using Satin Cast 20, centrifugal
casting, plenty of flux, and an oxygen acetylene torch. I have
altered about all the temperatures on the oven and metal to correct
the problem. Nothing seems to help. What do you expert casters think?

What metal are you casting? The problem you describe sounds like the
investment is breaking down from a combination of too much heat and
flux. Satin Cast and other plaster bonded investments are not
designed to handle the higher temperature metals they start to break
down above 1400 F. The combination of high heat and flux starts to
dissolve the investment . I also think that elemental silicon that
is alloyed in some metals contributes to the problem as I have
mostly seen this on silicon bronze castings. The bronze melts at a
little over 2000 F and with enough super heat to get it to flow is
probably in the 2200 to 2300 range. The resulting ceramic slag is
hard as hell and leaves pitting on the metal under it.

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160

Member of the Better Business Bureau

I used to use Satin cast 20 25 years ago and had the same problems
you are having. When the investment was new out of the container that
it was shiped in they seemed to cast moderatley good I then swiched to
Ultra cast and if the investment was over 6 monthe old I had the same
trouble.The heavy particles of the investment sank setteled to the
bottom of the container. That was what was causing the problem. I
then started to using my Scot Murry 12 lb tumbler to mis the
investment for at least a hour before using. I got a three gallon
plastic container with a lid from Gilleanios resturant and I attached
three pieces of aluminun at 120* apart inside . They were about 2"
wide and 7 to 8’ long.

I bolted them inside of the container withlid and it seemed to solve
the proble. Since I have switched to Ramson and Randolf investment and
I still tumble the investment for 1 to 2 hours before using and my
results have been 95% better. Hope this will help you.

Youra : Billy S.