# Thick film paste



## charrid (Aug 24, 2016)

Does anybody have a suggestion for reclaiming gold from raw unused thick film paste? The composition besides gold powder contains glass frit and high viscosity organic solvents. Normally the paste is screen printed on alumina ceramic and fired in a belt furnace at under 1000C. The glass bonds the gold to the alumina surface. I am a beginner with basic chemistry and metallurgy knowledge. Thanks.


----------



## 4metals (Aug 24, 2016)

The paste usually has an oil based solvent which is flammable (at one time it was pine oil). I used to get in jars of the paste for refining and all I did was open up the lids and light the paste and let it burn off. you could also put the open paste bottles in an oven to do the same thing. 

The main thing you are trying to do is burn off the organic, after that, it is routine aqua regia refining to recover the gold. Since the burning will not approach the melting point of the gold the resulting chunks are easily broken up with a mortar and pestle and they dissolve quickly. 

When I refined the paste, I also processed a lot of scrap called Kin Wipes. They were a lint free paper towel which was used to clean up the printing apparatus that they printed the thick film circuits with. Since what they were cleaning off was gold paste, they yielded heavily. All I had to do was burn the paper off in a metal can and process the ash in aqua regia. 

Thick film paste material is high yielding waste from the thick film hybrid manufacturing industry.


----------



## nickvc (Aug 25, 2016)

I remember we had a lot of those type of bottles come in to refine, they were termed gold paints I think from the pottery industry and we did exactly as 4metals suggested to you burn off the oil and refine the residues with AR, and yes they were high yielding


----------

