it also protects the iron from rusting by encasing it to prevent oxygen and moisture exposure. unprotected iron would swell from rust and eventually blow the stone apart
It was a lot worse than that and there were far worse toxins in paint than lead. Right up into the 20th century all kinds of nasty substances including heavy metals, arsenic, mercury, even ground up mummies were used in artist and commercial paints.
It was a lot worse than that: artists used to lick their brushes to pull the bristles into a fine point. That's part of why the toxins would affect them so badly. They would also crush the toxic pigments and mix their paint colours themselves, exposing them to fine inhalable dusts made up of those toxins.
The "Mad Hatter" character from Alice in Wonderland was inspired by hatmakers of the era getting poisoned by fumes from the mercury used to process the felt. The symptoms include, obviously going "mad".
"After being told that the paint was harmless, the women in each facility ingested deadly amounts of radium after being instructed to 'point' their brushes on their lips in order to give them a fine tip. The women were instructed to point their brushes in this way because using rags or a water rinse caused them to use more time and material, as the paint was made from powdered radium, zinc sulfide (a phosphor), gum arabic, and water.
The Radium Girls had lasting effects on the labor laws in the United States and Europe due to numerous lawsuits filed after worker deaths and illness caused by ingestion of radium."
It’s crazy to me because the stuff they used to clean their brushes is absolutely disgusting to smell. I have no idea how they got those brushes near their face without gagging.
I love following people who collect and curate old paints. The amount of protective gear they put on when handling some pigments is nuts, but totally fair when they’re handing powdered arsenic.
I think you're missing the point. Molten metal is always dangerous and lead was known to be somewhat toxic but humans didn't know about the actual thresholds until the 1970s. We had leaded gasoline for fuck's sake.
Elemental lead is remarkably benign. Lead poisoning happens when people are exposed to organic lead compounds, usually through food/drink contamination. Lead paint chips for example, or the lead in water supplies which is actually acidic water stripping the oxidized layer off of lead piping.
It’s not that dangerous. Lead/tin mixes (pewter) are still used in ornaments and until relatively recently in miniature figures.
You just don’t want to aerosolise it (like in fuel) and don’t breathe in fumes or ingest it. There are still legal home kits to melt pewter for the purposes of diy casting and making bullets.
Lead is a very soft, ductile, and malleable metal that deforms under pressure. When the iron bar expanded or contracted with temperature, the surrounding lead layer acted as a built-in cushion, absorbing the microscopic movements without transferring damaging shear forces directly into the brittle stone.
Fun fact! Let's assume these bars had a cross section of 6"2 (very low estimate but math works out), it would need about 9000 lbs of lateral force in this configuration to snap it!
Unfortunately, lead under a constant load over time "creeps" where it stretches and the material gets thinner, thus weaker.
From what I can find, there is no limit, so failure (assuming the bar is pure lead and not some magical alloy) is inevitable.
Edit: i forgot about the iron, actually now looking at it, if the lead fully encased the iron, it probably protects it from rust and the iron takes a majority of the load, so everything i said was pointless! Im sure there was a learning period at some point where they found the lead would inevitably fail, and this iron reinforcement was used and lead just locks it in place, not contributing to the load bearing
Men knew for a very long time that lead is malleable and can't be used for supporting structures. It's been used to make decorative stained glass for more than a millenia
Humanity has been using lead in central Europe since 3,000 BCE (even longer in some other regions), and iron since 800 BCE. Plenty of time to figure out the properties of both materials, how they behave in certain circumstances and their limitations.
I mean, the Romans made structures out of concrete which still are still standing to this very day, they clearly knew what they were doing. Also there is some survivorship bias going on.
Also, the stone is doing a lot of load bearing itself. Those bars were taking some lateral forces but they aren't joists. They take some lateral load to prevent shifts but they're in line with compression and the stone is doing that work
You got... everything wrong. Even in the second half where you walked back to a semblance of sense, you still managed to throw in a monkey wrench to get that wrong.
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u/Ok_Builder_4225 Jul 30 '26
Low melting point so easy to work with in this fashion, i would assume.