Metal Casting Zone

I was casting my first brass ingots form scrap pluming fixtures and I ran into a little problem, though I was not clear that it was a problem at first.

When I poured the ingots they were smoking pretty good and formed an ugly crust on the top that when cooled down was a dull dark yellow brown. I later used some of these to pour a casting that turned out badly

I din't have a photo of the ingot, but it looked like this



A few day later I had come across some more scrap brass from pluming fixtures and the ingots that I poured for this poured much better and cam out looking nice, with one of the crust that I has from before. I thought I might have done a better job skimming off the impurities, but thing got worse the second go.

I considered what I has don differently between the two groups and the second time I broke the brass sink valves down and removed all the rubber and plastic parts. This seems to be the logical problem, but being so new to this I cannot be sure, so I submit the question to you.

So was it the plastic and rubber, or did I do something else wrong? Is there any way to save this brass?

casting surface

I had the same problem when I first tried to cast brass ingots. All I could do is let them cool off then sandblast them, they looked fine after that. When I get around to melting more ingots im goint to try borax as a flux. I have been told that it works well and its cheap and its easy to find next to the laundry cleaners.

Just based on the pics, there could be a number of things wrong. I'd say it's not likely to do with the plastic fittings on the pipe valves, I've never bothered to remove any of that stuff.

Looking at the other thread you posted, my first intuition was an improper wax melt. However, seeing these close-up pics, I'm thinking it's more likely a flux issue. What are you using to degass your melt, and when? Are you adding flux at all, or just melting scrap pipe?

I think incomplete wax melt is also still a possibility, what's your melt procedure?

And then, there's the slag in the 2nd pic. Definately need to be skimming your melt before the pour, that'll make a world of difference.

You should be able to just re-melt this stuff. without adding anything, you can generally melt your brass 2-3 times before it just gets nasty.

I have not used anything as flux, just melting down the scrap. The mold was preped at 350 for 22 hours.

Your wax melt should be ok for that length of time, the only way i'd imagine there would be any wax residue leftover would be if your mold isn't inverted in the burn-out.

Try adding some borax powder to your melt, this will help degass the bronze, and cause the impurities to float so they're easier to skim off. Once your metal is melted, but before it's at full pour temp, sprinkle in a small amount of borax, then bring it up to temp, supposedly you can stir it in with a glass or graphite rod, but I've never done it that way.

Hopefully this will helps. Such are the perils pipe fittings! If you can find any big bronze/brass gears at your local scrap yard, they're usually higher quality metal, I use those whenever I can get them.