Recently I’ve gotten the urge to play around with polymer clay-- the kind sold in hobby stores that can be conveniently oven-cured in one’s own kitchen. It appears to be a very versatile medium, but the plastic clay itself doesn’t weigh all that much. I am hoping to give the sculpted objects a bit more tangible heft, and so it occurred to me to try filling them with heavier material.
Lead is proverbially heavy, and also nicely cheap and available in the form of fishing sinkers. However, given that it is also famously toxic, I am unsure just how much damage I would be risking by baking it in the same oven that I cook my food from. The plastic clay itself cures at around 100 - 130 degrees C, and theoretically the lead weights would be sealed inside. But what could happen if the clay cracks while curing? Would heated lead give off vapors at those temperatures? Would there likely be any practical danger from cumulative exposure? If so, might I be able to reduce any hazard by coating the lead further, say with liquid plastic clay or resin, or maybe wrapping it snugly in foil? I really have no idea how inherently hazardous my hare-brained scheme is, relative to eating delicious leaded paint chips.
It also occurred to me that I could avoid the whole problem a couple of ways, say by using weights of a less toxic metal like tungsten; but apparently tungsten is rather pricier, and I am extremely poor. I could also buy a small hobby oven specifically for baking polymer clay, but again: poor. If there’s no practical danger from heating up lead fishing weights, then I won’t worry about it. But if metal poisoning is a likely outcome, then I guess I’d better scrap the idea for now.
As long as the lead is completely encased in the clay, I think the risk of contaminating your oven is extremely low. Even if you got lead in your oven, you don’t cook directly on the oven surface, do you?
I don’t know if I would re-use the sheet you are cooking the weights on for food, though.
Vapors aren’t going to be an issue at temperatures below lead’s melting point: 327 degrees C. For significant danger, you need to heat it well above that.
But lead in the kitchen probably isn’t the best possible plan. Perhaps you could use steel (e.g. steel shot) instead?
You might also look into lead-free solder, preferably without a flux core. It has the advantage of being bendy, so you may be able to form it into a wire frame around which you would be able to wrap the plastic, but it also might not be heavy enough for your purposes. Just make sure to get something that has a higher melting range than the plastic stuff cures at.
Polymer clay has its own unhealthy vapors. A lot of polymer artists bypass their own ovens and use dedicated toaster ovens, just to be on the safe side.
I make most of my own fishing lures - curing lead based jigs that have been powdercoated is a common thing to do -
An inexpensive toaster oven in the garage is the way to go - lead ‘fumes’ is in and of itself not the issue (as stated above - you have to get well above the melting point to get to that level) - its more the idea of the ‘stuff left behind’ that might get into your food, etc.