# One more bar



## MGH (Sep 15, 2015)

Hi all,

Except for Solar’s re-melted button, and new button, seems like it’s been a while without new pictures. This is 1.145 ozt. It was a combination of several small batches of different materials: mixed gold filled, pocket watch cases, karat gold, and a few small BB’s that had been stuck in my melting dish from previous batches.

I ran each of the smaller lots through a single refining and then melted them individually to get a measure of the yield from each type – and in some cases the person it came from. Then I ran all the melted pieces through AR again. I wasn’t surprised to find a low yield of 1.19% in “gold filled” from one source while the other gold filled group came in right at 3.0%. There was obviously some trash and plated material in that 1.19% lot. Sometimes you have to be more discriminating when you take in material. But no worries; live and learn, and that low yield is not related to anyone on this fine forum.

The second picture is another taken with a staged microscope at work. We still couldn’t figure out how to avoid the glare. The microscope has built in lighting circling the lens. We even tried turning that off, and bringing in auxiliary light from the side, but that was no better. Anyway, here are the pics.


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## g_axelsson (Sep 15, 2015)

Nice! These pictures always brings a smile to my face. 8) 

To avoid the glare you should use polarized light with a crossed polarizing filter on the objective lens. That kills off direct reflections from the light source.
But with a shiny object like this it creates an almost black object as there is almost no diffused light. You could try to make a light tent to make the light source diffuse enough.

Göran


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## Anonymous (Sep 15, 2015)

Nice advice Goran. You're always so good on the theory.


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## g_axelsson (Sep 15, 2015)

Thanks, too bad the theory doesn't always agrees with the reality! :lol: 

I had some experience with photographing shiny silver coins, they turns almost black when the reflected light is reduced, like this




(not my picture)

The dark and white background of the portrait is the reflection of the background in the mirror finish of the coin, by having the background far beyond the focus depth of the camera it get's very diffuse.
In microscopy they make observations in two basic ways, bright field when the lighting is right behind the object so the surrounding is also bright, and dark field where the light shines in an angle that it doesn't enter the objective. The only light going to the eye is light reflected from the object observed.

Then add in some basic physical principles and tinkering a bit with computer graphics and rendering scenes and you get some extra tricks in the baggage. 8) 

Here is another example of what I like to call "dark field photographs" of a white shiny silver coin.



(not my picture either)

Göran


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