Brass has always given me troubles as well. Not sure if the alloying constituents boil off or what happens, but, I generally try to talk my customers into bronze instead. If they still want brass I cast it at as low a temperature as it will flow and it generally comes out well. Good luck
Axe first pour try, metal too cool ? Poured flat with gate at handle end, vent at blade edge. Small dagger second pour try, metal too hot ? It was poured vertical from handle top. I tapped the bubbles with a ball peen hammer so the extent is not visible. Both were poured in PoP molds made by lost wax method and slowly preheated before casting, neither mold failed. Thanks, John ,,,,
I agree, last week I melted brass and quickly it started belching green flames and zinc fumes so I had to put my respirator on. Maybe metal too hot, but contained a lot of dross (oxidized zinc ). Then I did the same casting in bronze (95 Cu /5 Sn) which was completely without fumes. And the casting succeeded. In your case, zinc vapors might cause bubbles when it freezes too quickly (metal too cold). The boiling point of zinc (906 C) is below the freezing point of brass.
your Mold was not dry POP is not a molding media it entrains moisture that comes out with the heat and has to go somewhere , it will work sometimes on very low temp alloys, getting it to work in brass is extremely unlikely, one of these college educated folk will explain the Whys I just know you dont do it, it wont work!!! you all need to stop bad mouthing Brass, or at least explain your issues so we can try to help , I cast BRASS dern near every weekend, and make HUNDREDS of castings from nothing else, there is no trick!!! it is not difficult!!! I think some of you are just Jumpy when it starts to Flare and smoke, get over it! that's like a blacksmith being afraid of sparks! it's a part of metal casting! V/r HT1 P.S. if you are having trouble with BRASS I will tell you how to Successfully cast it, Just ask
start by buying a real casting media, not POP decide what process you want to use , LOST : foam, wax, ect. sand, Deft clay petrobond, green sand CO2 sand, a two part Binder system etc.. once you have decided how you wanna cast , then we can discuss, techniques V/r HT1
