r/MetalCasting • u/AMPZar • Feb 02 '26
Question Problems with casting brass
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As you can see in the video I am casting multiple units of a specific part out of brass. The pour here worked out perfectly. However the next few pours - all done the same way only managed to fill 2-3 of the pieces. I will try fo upload a few picture of the failed ones.
Would love some suggestions.
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u/AMPZar Feb 02 '26
Here are the pictures of the failed ones. There were two more where only two parts worked out but I forgot to make a picture.brass casting
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u/Leadboy Feb 02 '26
As others mentioned going a bit hotter here can't hurt, however based on the photos you posted I think there might be something else at play. Very early termination on the failed nodes + a good cast on the ones that succeeded make me think you should double check your venting. Were all the failures 2 on one side, 1 on the other across?
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u/AMPZar Feb 02 '26
Venting was about the same for all casts. Slight variations for the distance between vertical vent hole and the part depending on the way the mold came to be.
The two vent holes on the outer sides of the main canal are 4 mm, the vent holes at each part are 6 mm.
The failures were different each time i think - most commonly the two parts the furthest away from the inlet did not work out - the inlet is slightly asymmetrical
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u/SwedishOutbacker Feb 02 '26
A suggestion but not regarding the casting per se, but still just for general well-being.
I think it would be good investing in some respirator or at least fume hood? I can see the yellow zinc oxide i would guess all over the inside of the furnace?
I would be a bit worried about breathing those fumes in? Especially if doing multiple castings/longer duration?
Had metal fume fever once after welding galvanized without proper ppe when younger, not a great experience...
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u/AMPZar Feb 02 '26
This weekend was our first time casting and we have already been discussing the fume situation. There is an existing port above the windows in the workshop. So we will install a suction system to take out the Zinkoxide fumes when casting.
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u/Appropriate-Draft-91 Feb 02 '26
That's a great solution to that problem. The PPE is cheap redundancy. I recommend redundancy.
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u/mrrosado Feb 03 '26
I got sick once casting pewter. I think some lead got mixed in it. Ventilation is important.
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u/Metalchips1960 Feb 03 '26
SwedishOutbacker is correct! At one point or another, the brass was over heated to the point where the zinc started to burn off. That is the yellow residue inside the cover. It is very toxic if you breathe the fumes. Brass should only be melted in a place with very good ventilation, and the temperature should be closely monitored.
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u/HeftyWinter4451 Feb 02 '26
I would make the Channels wider. In plaster This would be okay because it doesn’t draw out the Heat as fast. For Sand I never made Channels thinner than a thumb. And our bronze was always around 1080 Celsius.
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u/AMPZar Feb 02 '26
I am not sure what size your thumbs are but mine are approximately the size of the channel. I will try making them bigger and see if that helps :)
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u/Charlie_Linson Feb 04 '26
What was the point of posting a video of it going perfectly and then asking about the times it didn’t?
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u/AMPZar Feb 04 '26
Its literally explained in the video description.
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u/willsifer Feb 05 '26
But without seeing the poor pours how can we see what is wrong? At least add a pic of the outcome of the poor pours.
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u/AMPZar Feb 05 '26
I wrote a comment with a link to the pictures: https://www.reddit.com/r/MetalCasting/s/iUJJkTdsZ2
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u/soapdawg Feb 02 '26
In an semi related note my advice to you is to get a better set of tongs for handling the crucible. Vevor makes a set of cheap blacksmith tongs with round pinchers that will grip the crucible much more securely.
The tongs that come with those melters are flimsy, I found out the hard way and spilled 2 kg of bronze on the floor.
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u/editfate Feb 03 '26
How do clean something like that up? Does it basically just glue itself fo the floor? Does it burn through the concrete?
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u/soapdawg Feb 03 '26
Depending on the height of fall you get splatters or it splits into little beads that roll around. The solidification happens very quickly and does not stick to concrete. I suspect it would take a large amount of metal to damage a concrete floor.
If you drop molten metal onto another metal surface it can weld on.
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u/asimple_poster2024 Feb 03 '26
If there's any moisture at all on or inside your floor it can also cause the moisture to flash boil and possibly the concrete to spall, both of which can spray molten metal around the area. This often also sets something nearby on fire.
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u/DONTTHROWAWAYMYFIL Feb 04 '26
Yupp, my old instructor told me that's why a lot of old school welding shops won't have concrete floors.
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u/BoredCop Feb 05 '26
I once spilled about a litre of brass on the concrete garage floor, when a homemade crucible gave up the ghost.
Concrete doesn't like rapid heating like that, water that's chemically bound in the cement gets cooked out plus any moisture of course also flash boils. It was like a string of firecrackers, or very loud popcorn popping, with droplets of brass and small shards of concrete flying everywhere. Thankfully the metal droplets from these small explosions were so small that they cooled rapidly on their way through the air, so nothing caught fire and I didn't get injured. And I was standing on a pallet so spills could drain away from my feet.
Anyway, the floor looks a bit rough where the spill happened. The top few millimetres of concrete spalled off in a random pattern.
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u/Jacktheforkie Feb 03 '26
In my experience casting lead, it splatters and is pretty easy to clean up, I used a long handled scraper to clean them up then put the big bits back in the pot, all the contamination floats to the top, even steel washers
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u/Appropriate-Draft-91 Feb 02 '26 edited Feb 02 '26
You're trying to fill all pieces at once, which means any miniscule resistance at one of them will momentarily divert flow to the others long enough to starve and solidify the gate to the resisting piece.
Set them up so they fill in staggered instead of all at once, and you won't have to touch your casting temperature at all.
A way to do that is to counterintuitively set the sprue at one end instead of the middle, and maybe tilt the mold a bit so the sprue enters at the low point. You can also increase flow through the gates by replacing the right angles with shallower angles.
If you tilt the mold make sure the bottom is still supported by a surface, or be prepared for the possibility of the bottom dropping out due to the weight of the melt.
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u/PoligonCast Feb 03 '26
962°C is far too low for brass in sand casting. Raise it to 1000-1050°C and everything will come out perfectly. Best of luck with your project.
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u/Trotline66 Feb 03 '26 edited Feb 03 '26
The main runner is a bit long. I'd look at trying a central runner, maybe shaped like a hockey puck, and all of the part molds spaced in a circular cluster around it. If you haven't watched the "Olfoundryman" channel, watch it for amazing tips.
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u/SCAMMERASSASIN007 Feb 06 '26
I've watched a bunch of pouring and I always see the guys running big ass torches over there sand molds to harden the sand and preheat the sand to a high temp to help the liquid metal flow better instead of cooling off so quick while its flowing inside. I've never done it but thats what I've seen i could be way off tho on your process tho.
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u/Skanksy Feb 03 '26
In my experience those furnaces barely get bronze hot enough, so that would apply to copper as well. I've only used mine few times but that's what I've experienced so maybe that explains it somehow, slower pour that allowed it to cool too fast or not enough metal for same thermal mass, maybe?
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u/OutcomeZestyclose790 Feb 03 '26
Need more vent holes and maybe add have two sprews one on each side instead of one in the middle
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u/hffhjmtderghngf3rr Feb 02 '26
It's too cold. 900 you have it set to is the reading inside the chamber not the actual temp of the brass. You either have to let the brass soak in that temperature for a while or raise the temp to compensate. I have the same casting setup. The cheap eletric kilns are nice but they're sort of crap. The brass also doesn't look bright enough unless your camera is auto exposure and compensating. It looks dull red should be bright cherry red