Low Melting/Vaporizing Cast Material?

Web search; "lost wax method". It is used for some sculptures

It is also used for casting jewellery!

What material, and, type of object are you trying to cast in it?

This may not be relevant but have you looked at 3D printers?

A material that can be dissolved in some liquid is also preferable. I am using copper vapor so its needs to withstand at least 150deg C and the ideally, dissolve/melt/vaporize away

Polyvinyl alcohol may work. Not sure how thick it can be cast though.

Copper boils at 2562°C (4644°F), so copper vapor will attack anything that melts below that.

Why not tell us what this is for?

Anybody can look up the boiling point of copper.

Read up on Chemical Vapor Deposition (CVD)

Agreed!

Good exhaust ventilation is very important using this alloy.

I have used an alloy of Cerrobend alloy as filler during tube bending. Removal of the cast metal is as simple as immersing in boiling water.

Caveat: Cerrobend contains about 10% cadmium. Fumes from cadmium are toxic, and known to cause liver, lung, and kidney failure and has been causally linked to various forms of cancer.

lost foam, Most metals pours will vaporized it in the pour. Like said before. lost wax can be removed from plaster cast with a few hundred degrees F. heat, steam, hot water it all depends on the wax and plaster used. There a alginate.form it around what you want. Make a cast in wax form, form plaster cast around that, then melt wax out, cure plaster, put molten metal in.

Are you making originals one offs, copies, production runs. Are you needing to making positive or negatives molds there strengths and weakness in all methods.