Hi. Some research lab just shut down (some kind of solar project involving advanced electrodes) and is dumping things on ebay that are normally VERY hard to get for private parties.
One thing is numerous sheets of copper foam various sizes:
They are very pretty, very light (mostly air; density in the grams/meter cubed).
They are open-cell, so you can fill the voids if desired, or filter through them.
I could picture these in an art, jewelry or electrochem project.
https://www.ebay.com/itm/1pcs-Copper-Cu-Foam-Plate-Sheet-Size-100-100-5mm/302261968796?hash=item4660379f9c:g:HUwAAOSwDKtY1La-