reply to bronze color

[ned]

hi, thanks for input. I agree about boiling off the silicon ( looked up boiling point after posting ). Investment had been in the kiln for 32 hours so was dry, I had wrapped plaster bandage around prior to casting and this had dried , however I suppose some moisture could be absorbed by the investment although the core was around 450 - 500 degrees C  before pour. Crucible only used for silicon bronze, heated to 700 C and allowed to cool  a bit before re heating prior to charge being added. All metal was sprues, gates and ingots along with some finished cast pieces as apposed to actual scrap metal. All metal is pre heated in flame up to 450 - 500 degrees to drive off any moisture. Never used degasser before, although not having any issue with porosity in the cast ( decorative items ) I could grind the pink off but couldn't damage finished surface. Color didn't matter in this instance but wanted to find out the cause.

Using silicon bronze so no zinc.

I use a coagulant flux after charges melted to hold all the slag when pouring.

Lost wax casting using proprietary bronze investment powder. Definitely no wax left in mould, have first hand experience of Vesuvius eruption caused by incomplete burnout.

Thanks again