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Gold Plasma

Posted: Mon Jun 04, 2018 3:58 am
by Tyler Meagher
I wanted to make some plasma with my vacuum pump. I used the magical gold plasma machine. I put a silver coin into the plasma and it turned gold. Sometime later I’ll figure out how it works.

Tyler

Re: Gold Plasma

Posted: Mon Jun 04, 2018 8:35 am
by Jerry Biehler
You sputtered a thin layer of something on there.

Re: Gold Plasma

Posted: Mon Jun 04, 2018 12:58 pm
by Samuel Berman
I can think of two other ways in which the color could have been created:

1. Some coins have copper on the inside and just a thin plating of the silver colored surface finish. When heated, the copper can alloy with the surface material and create a gold colored layer.

2. It could be an oxide layer, but since this is under vacuum that is unlikely. However, I guess it could happen if you removed the coins while they were still hot or left them in for a long time?

Just some of my thoughts.

Re: Gold Plasma

Posted: Mon Jun 04, 2018 2:53 pm
by Bruce Meagher
The machine is a small gold sputter coater. Turning pure silver coins into gold... now that's just straight up good magic.

Re: Gold Plasma

Posted: Mon Jun 04, 2018 9:18 pm
by Richard Hull
Yeah, some deposition tinting the coin. Will a good rub with silver polish remove the patina?

Richard Hull

Re: Gold Plasma

Posted: Tue Jun 05, 2018 8:30 am
by John Futter
Richard
Yes it will
that unit is made for coating SEM samples that are not conductive so that there is no charge build up and the gold ions arrive with almost no energy so that especially biological tissue does not get damaged
This of course means that there was not enough eV to do a chemical bond so that the film does not become part of the surface

Re: Gold Plasma

Posted: Tue Jun 05, 2018 2:26 pm
by Rich Feldman
How about measuring the gold thickness progression at home?

You could sputter onto glass. Then compare optical density of the film with some handy reference.

Or open up a crystal oscillator (or plain frequency control crystal), and watch the frequency change as gold piles onto the quartz.
That principle is used in some industrial deposition monitors. Beware of the thin film electrically shorting the circuit.

Re: Gold Plasma

Posted: Wed Jun 06, 2018 8:23 pm
by Bruce Meagher
Great suggestions Rich. Two experiments to add to the list.

Bruce