If you want a yellow color, you can add zinc to silicon bronze or buy "silicon brass" from Atlas Metals in Colorado (they ship). I think their silicon brass is the same as 513B silicon bronze. It has about 15% zinc in it. I've added more zinc to about 30%. At 30% it's nice yellow and much easier to cut. I've made hundreds of belt buckles with it.
--- In firstname.lastname@example.org, "ferroman1000" <ferroman1000@...> wrote:
> thank you for your thoughts. I have tried sand moulds for round bar but the same thing happens. If I pour very thin brass castings in sand there is no porosity. I suspect that the longer brass stays liquid in sand or steel moulds gas is given off at the mould metal interface so porosity is always confined to near the surface. The problem may be solved by appyling a graphite coating. The brass I use is plumbing fittings and is always diecast. I have used maganese bronze and is alot easier to use but I have runout it so I use what i can get hold of. Trying to identify scrap brass can be a extremly difficult problem. Casting brass is the most difficult metal for me as I found bronze so easy to cast but there are times where i need the yellow color for some jobs.