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Thread: Bronze toxicity?

  1. #1
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    Default Bronze toxicity?

    So I am planning on making a few of the little stoves that my dad designed years ago, and in the past they have had a bronze star mounted on the face of the stove. Someone on the internet told me that bronze is toxic when hot. He had a story about someone mounting a bronze star on a Sardine stove and getting really sick. ANyone ever heard of that before? I could see impure bronze causing a problem when liquid but I have never heard of anything like this. A quick googling hasn't turned anything up.

  2. #2
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    Default Re: Bronze toxicity?

    You need to be careful when melting bronze that is alloyed with zinc. The zinc vaporizes before the bronze reaches pouring temp and can be seen as white smoke. Silicon bronze contains no or little zinc and is relatively safe to melt, but standing upwind is always wise..

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    Default Re: Bronze toxicity?

    Never heard of any such thing.
    Chuck Hancock

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    Default Re: Bronze toxicity?

    The only two things commonly alloyed in copper that could even remotely cause concern are lead and zinc, and the lowest melting point of either of these is over 700 deg F. If your stove has reached this temperature, you've already burned the toast.
    Chuck Hancock

  5. #5
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    Default Re: Bronze toxicity?

    Yes, bronze can be toxic at higher temperatures --a blacksmith friend of mine has some interesting cautionary tales of forging bronze, and the toxicity is apparently the source of the archetypal lame/deformed smith (from pre-iron age metalworking)-- but I don't know the chemical details and I'm not sure you would reach those temperatures with a stove ornament. Have you tried a web search for "bronze toxicity"?

    Alex

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    Default Re: Bronze toxicity?

    There are many copper alloys, some indeed have toxic fumes. If you used Everdur, or another simple alloy of Tin-Bronze it may be OK. But just a star of yellow metal? Not so much.

    wiki

    "... Initially, bronze was made out of copper and arsenic, forming arsenic bronze, or from naturally or artificially mixed ores of copper and arsenic,[6]with the earliest artefacts so far known coming from the Iranian plateau in the 5th millennium BCE.[7] It was only later that tin was used, becoming the major non-copper ingredient of bronze in the late 3rd millennium BC.[8]Tin bronze was superior to arsenic bronze in that the alloying process could be more easily controlled, and the resulting alloy was stronger and easier to cast. Also, unlike arsenic, metallic tin and fumes from tin refining are not toxic."

  7. #7
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    Default Re: Bronze toxicity?

    During the pour out while smithing I get it, but not for a cast star mounted to a wood stove.

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    Default Re: Bronze toxicity?

    If the story is true, the star must have been brazed to the stove with brass filler metal, and the exposure was only during that operation. As the others have said, it happens mostly during melting and forging of brass. The stove should never get hot enough to have a problem with a brass star (40% zinc) and a bronze star has no zinc.

    Metal fume fever causes flu like symptoms mostly in foundry workers or welders. There is a list of operations near the end of this: https://www.cdc.gov/niosh/docs/81-123/pdfs/0675.pdf There are other metals listed on the Wikipedia page.
    Last edited by MN Dave; 05-10-2017 at 02:12 AM.
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  9. #9
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    Default Re: Bronze toxicity?

    That's my understanding. The stars have threaded studs in the back side and there is a tapped hole in stove.

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    Default Re: Bronze toxicity?

    Isn't the "Sardine" stove rated for coal?
    I routinely used to run my little iron stove with glowing red sides before I paid much attention to the damper.

    (Lots of brass stars out there, a stud cast on the back, they bolt on. Made in Thailand of some mystery yellow metal - cheap....)

  11. #11
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    Default Re: Bronze toxicity?

    Naval Bronze often contains a bit of lead to improve machinability.
    However, I have never heard of anyone being poisoned by it or any other bronze alloy. The guys at the Port Townsend Foundry would be wearing toxic fume masks during a pour if that were true!
    Jay

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    Default Re: Bronze toxicity?

    Quote Originally Posted by Jay Greer View Post
    Naval Bronze often contains a bit of lead to improve machinability.
    However, I have never heard of anyone being poisoned by it or any other bronze alloy. The guys at the Port Townsend Foundry would be wearing toxic fume masks during a pour if that were true!
    Jay
    Ha ha! Frankly Jay, often times they should. But the conversation here has fuzzed up somewhat. Some speak of solidified metal at temps within the normal operating range of a solid fuel burning stove, others of metal at forging or casting temps. These are two different things. It's also been made clear that "bronze" is an insufficient descriptor to address any specific application.
    Chuck Hancock

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    Default Re: Bronze toxicity?

    Yes, there's some inconsistency in the responses. Could be that my writing isn't as clear as it could be or it could be folks may have missed my main question (toxicity of solid bronze that is in contact with a hot wood stove). And then there may be some of the usual bronze/brass trouble (down with zinc!). As a rule of thumb aggressive ventilation system is a good idea with doing hot work and/or a respirator. The other thread on FB where the concerned was expressed spoke of A3 as a grade of bronze.

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    Default Re: Bronze toxicity?

    YMMV ... but I've had a couple times when I felt like hell after a bronze casting workshop. Sort of like a mild flu that lasts a half day or so. I think I have an allergy of sorts to the offgassing / exhaust. Because of this I'm probably done with bronze casting.

    Maybe it's this ... https://en.wikipedia.org/wiki/Metal_fume_fever
    Quote Originally Posted by James McMullen View Post
    Yeadon is right, of course.

  15. #15
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    Default Re: Bronze toxicity?

    (toxicity of solid bronze that is in contact with a hot wood stove)[/QUOTE]
    Exactly, and that was the question to which I responded. Yeadon, there are so many noxious fumes possible in a pour,... not least coming from the mold itself what with all the potential binders, sleeves, and screens possibly present,.. it's no wonder that you may have been exposed to something irritating.
    Chuck Hancock

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    Default Re: Bronze toxicity?

    Quote Originally Posted by Yeadon View Post
    YMMV ... but I've had a couple times when I felt like hell after a bronze casting workshop. Sort of like a mild flu that lasts a half day or so. I think I have an allergy of sorts to the offgassing / exhaust. Because of this I'm probably done with bronze casting.

    Maybe it's this ... https://en.wikipedia.org/wiki/Metal_fume_fever
    Which is why I have an open cupola and an extractor fan above my furnace, I use a fair bit of manganese bronze and it contains zinc and produces zinc fumes.

    A photo, the furnace is at the right end of this building below the vent.

    Last edited by PeterSibley; 05-10-2017 at 02:37 AM.
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  17. #17
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    Default Re: Bronze toxicity?

    toxicity of solid bronze that is in contact with a hot wood stove
    Sorry McKee, I tried to address that --"I'm not sure you would reach those temperatures with a stove ornament"-- but I got carried away with other details and muddied it up.

    Unless you're running your stove a lot hotter than is probably good for the boat, I'd be more worried about carbon monoxide or inadequately-vented combustion byproducts making you feel sick than anything the bronze would off-gas.

    Alex

  18. #18
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    Default Re: Bronze toxicity?

    I would go back to the table and ask about ventilation on the cases
    where people got sick from using a stove with bronze ornaments on it.
    - Carbon Monoxide comes to mind - not fumes from the ornament itself.

    does that seem more viable ?


  19. #19
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    Default Re: Bronze toxicity?

    Although I have never heard of anyone being poisoned by a bronze star on a Little Cod stove front, the brass rails on a Shipmate cook stove or a tin lined copper cooking pot, I have heard of some people who tend to sift fly specs out of pepper in order to sound knowledgable. In my humble opinion, a cast iron stove is superior to one made of bronze. Otherwise Herreshoff and the rest of those who chose to heat with wood or coal would have chosen bronze over Iron for stove construction. Sometimes, a solid fuel stove will heat to nearly the temperature needed to melt bronze. My Tiny Tot once glowed red burning coal.
    Jay

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    Default Re: Bronze toxicity?

    Yea, what Jay said: "...some people ... tend to sift fly specs out of pepper in order to sound knowledgeable."

    Smelting and casting processes should always be done with at least plenty of ventilation, but a cast ornament or fitting on a stove isn't going to do anybody a bit of harm. (Regardless of whether the State demands that a sticker go on it warning that it might cause cancer!) There are many stoves with brass and bronze fittings which have never hurt a fly. I had a Lopi wood stove with a cast brass door. Used it for years in the house with no ill effects whatsoever, so "not to worry" about your bronze star.


  21. #21
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    Default Re: Bronze toxicity?

    Quote Originally Posted by John-1948 View Post
    I would go back to the table and ask about ventilation on the cases
    where people got sick from using a stove with bronze ornaments on it.
    - Carbon Monoxide comes to mind - not fumes from the ornament itself.

    does that seem more viable ?
    Yes.
    '' You ain't gonna learn what you don't want to know. ''
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  22. #22
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    Default Re: Bronze toxicity?

    Good looking door! Every coin has its flip side. I just try to use a bit of common sense.
    Jay

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    Default Re: Bronze toxicity?

    Quote Originally Posted by McKee View Post
    Yes, there's some inconsistency in the responses. Could be that my writing isn't as clear as it could be or it could be folks may have missed my main question (toxicity of solid bronze that is in contact with a hot wood stove). And then there may be some of the usual bronze/brass trouble (down with zinc!). As a rule of thumb aggressive ventilation system is a good idea with doing hot work and/or a respirator. The other thread on FB where the concerned was expressed spoke of A3 as a grade of bronze.
    Your question was clear enough. The answers were also unanimously saying that there was nothing to worry about.

    If there was some confusion in the answers it was the detail that was added to show that the respondents know a thing or two and wanted to establish some credibility. The story about a bronze or more likely brass star causing a problem could have some basis in fact, but the conclusion that the star caused a problem as used on the stove was wrong. Most of the answers went into detail about common confusion between brasses and bronzes and the significantly different circumstances that can generate fumes.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  24. #24
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    Default Re: Bronze toxicity?

    One would presume that in order to generate fumes, the bronze or brass would need to be in a molten state. Very unlikely for a stove fitting! Is the horse dead yet?
    Jay

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    Default Re: Bronze toxicity?

    I think the metal would have to pass beyond the liquid state and turn to gas before it was an issue. Having been around hot dip Galvanizing plants, even here in California there seems to be little concern for molten Zinc.
    But... having welded the occasional galvanized part, that stuff can be nasty.

  26. #26
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    Default Re: Bronze toxicity?

    While we are flaying the horse's carcass, we might as well mention that:

    We are talking about too much of a good thing:
    http://www.medicalnewstoday.com/articles/263176.php

    Galvanizing fumes are controllable:
    http://www.tandfonline.com/doi/pdf/1....1960.10467904

    The vapor pressure of zinc is calculable, but I don't want to do it:
    http://mmrc.caltech.edu/PVD/manuals/...20pressure.pdf

    Last, and certainly least, You shouldn't use the brass star if your ship is a spaceship unless it is nickel plated:
    vacuum-compatible-metals-and-alloys
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  27. #27
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    Default Re: Bronze toxicity?

    Thanks for the responses!

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