Mehron says they no longer sell metallic powder in large quantities i.e. Kg, only in one ounce bottles. Is there another supplier for amounts that allow messy play, thick mixtures, dunking etc?

I honestly didn't know they sold them in anything but the little bottles. I see it sold in bulk containers by wholesalers like Northwest Graphic Supply that seem to be at least art-adjacent and not industrial, but it's not like the kilo bricks of gold powder I've seen shown off by Japanese producers.

I guess there's no real demand in that application.

You can buy equivalent metallic mica powders (ie ground metal powders) in 1kg from specialist craft and paint suppliers but it's not really any cheaper per volume and little consideration in its composition would have been given to human contact (although it's essentially the same - like buying non food grade peanuts).

Since this type of pigment remains opaque mixed with 95 percent medium (necessarily an oil or solvent) the thickness and texture of the substance you create is mostly reliant on the medium. Adding too much more than 5 percent seems decadent but is logically pointless and astronomically expensive.

I don't know what the solid bars constitute but they are logically mostly a vehicle or medium (a solid like butter or wax?)