[kragen]

this sounds more entertaining for 3-d printing things that startle people by being staggeringly heavy rather than things that are actually useful

it should be heavier than lead; lead is only 11.3 g/cc, tungsten is 19.3, 75% tungsten would be 14.5, but then the other 25% is petg with sp.gr. ≈ 1 so you should actually get a density of 14.7

but i struggle to imagine cases where using tungsten is a more cost-effective option than using lead and making the object 9% bigger? they cite 'various medical applications' but tungsten isn't exactly ideal for permanent body contact either

oh actually they say it's 75% tungsten by mass, not volume, so it's only 4 g/cc, and so its attenuation (at 140keV) is only 18% of lead's (by volume)

copper might be an alternative that is less toxic than lead and less expensive than tungsten

[scythe]

If it's only 75% tungsten, I'm figuring it's a tungsten powder. I work with lead all the time but I would not fuck with lead dust. Lead sulfide would be much safer, although studies feeding it to rats did show elevated lead levels.

That said, no metal dust is very nice. Solid lead might be safer than tungsten powder. Maybe you could make an iodinated polymer or use a barium cement.

[kragen]

my candidate list of high-density fillers from dernocua (sorry for markdown) is

- Osmium: [US$13000/kg][8], 22.65 g/cc, or possibly iridium at more than twice that price

- Tungsten: [US$30/kg][9], 19.3 g/cc

- Tungsten carbide? Not sure what it costs but its density is 15.6 g/cc.

- Lead scrap: 95¢/kg, 11.3 g/cc

- Steel scrap: [21¢/kg][10], 7.9 g/cc

- Magnetite: [10¢/kg][11] [or so][12], 5.2 g/cc

- Quartz (as construction sand): 3¢/kg, 2.6 g/cc

- Water: [.06¢/kg][22] or so, 1 g/cc

[8]: https://www.metalary.com/osmium-price/ [9]: https://www.metalary.com/tungsten-price/ [10]: https://www.usgs.gov/centers/nmic/iron-and-steel-scrap-stati... [11]: https://www.usgs.gov/centers/nmic/iron-ore-statistics-and-in... [12]: https://stockhead.com.au/resources/barry-fitzgerald-why-magn... [22]: http://www.scientificamerican.com/article/israel-proves-the-...

this is my approximation of the pareto frontier; that is, each of the items on the list is conjectured to be cheaper than everything that's denser than it is, and denser than everything that's cheaper. corrections are welcome

i was thinking baryta (46¢/kg, 4.48 g/cc), mercury, litharge, minium, cinnabar, cupric oxide (US$3.90/kg, 6.315 g/cc), zinc oxide (US$29/kg, 5.6 g/cc), and manganese dioxide (5.026 g/cc) might be interesting in this context too

i hadn't thought of your suggestion of galena (just cinnabar) and generally i'm skeptical of metal sulfides because of their tendency to produce hydrogen sulfide; i don't think that's an issue with those two. litharge, minium, and mercury are a lot more worrisome toxicologically

i don't have solid pricing information for mercury, litharge, minium, cinnabar, or galena, and i'd be interested

tungsten is probably more chemically inert for medical purposes than a lot of these

[scythe]

Density alone is a weak parameter. For photons with energy below 200 keV — that is, most of them — the attenuation is proportional to Z^2, so barium with atomic number 56 is four times as attenuating as nickel with atomic number 28, and lead with atomic number 82 is about twice as effective as barium — all of this before you account for density.

I've done a bit of searching for materials myself. Barium is mined as barite (BaSO4) or witherite (BaCO3), not baryta (BaO*xH2O, caustic), and USGS lists the price of barite as $180/t, or $0.20/kg.

You also have a K-edge effect, which prompted me to wonder whether you can easily produce barium zirconate from the respective ores, which are both cheap — BaZrO3 (sg ~5.5) is not currently manufactured (Zircon sand was <$1/kg until a COVID-related shortage). But at this point I decided I was overthinking it.

[kragen]

baryta is barite, not baria. baria is not just caustic but also toxic and prone to produce dangerous peroxides

i think the price i cited for it is retail, locally

i was interested in density for psychological effects when i made the list

thanks for the tip about barium zirconate; it sounds very promising. how about lead zirconate?

[hakfoo]

I'd think the public palatability of lead products is one aspect. People don't worry as much about tungsten.

I was thinking weights to fit specific items. Model railway wagons, for example, need to be weighted and balanced to operate smoothly, but you have significant size constraints. I threw a bunch of tungsten weights inside a small locomotive to give it extra tractive effort.

[kragen]

yeah but it turns out this is only 4 g/cc