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-   -   adding gold to batch (http://talk.craftweb.com/showthread.php?t=11705)

Bradley Howes 09-13-2017 03:33 PM

adding gold to batch
 
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Hello All,

I was doing some research for my art history class at Alfred University and I came across a cage cup known as the Lycurgus Cup. The green photo is when the cup is lit from the front and the red photo is back lit. I was reading about the composition and it has about .0005% gold as well as silver and manganese. I'm wondering how one adds gold to glass batch. I know you have to dissolve the gold in aqua regia (very nasty). From there, historically, tin has been added to make Purple of Cassius which I believe is a powder. However, on Instagram, I saw a post where someone poured a solution, I don't know if this was the aqua regia with auric chloride or something else like a gold solution with some thing else added, straight onto the batch which was then mixed and other oxides added.

I'm really interested in this because this is a glass that becomes completely different based on how its viewed. There's a duality to the glass, similar to rare earth glasses that change color or uv reactive glasses like uranium.

Pete VanderLaan 09-13-2017 04:25 PM

Gold glasses can liver in reflective light if the molecules get big enough and I suspect that's what you are seeing. I make a gold chloride solution for my rubies and then mix it in gold sands. My friend john just pours the gold chloride into the batch,
There are three important things in the receiving batch, Gold , lead and selenium.

Mike McCain 09-13-2017 04:28 PM

Color changing glass, Alexandrite. It's a whole wasps nest of philosophical quandaries. Carving cage cups must be the most labor intensive habit ever dreamed up by a glassmaker.

Pete VanderLaan 09-13-2017 05:50 PM

That's ignoring the glass in itself Mike and that's the question. What's a molecule to do?
Look at the shadows in the two pictures. One's reflective and the other transmissive.
Just melt a simple gold ruby glass. God knows it isn't rocket science anymore and you do learn a lot.

Bradley Howes 09-13-2017 08:45 PM

Quote:

Originally Posted by Pete VanderLaan (Post 136745)
Gold glasses can liver in reflective light if the molecules get big enough and I suspect that's what you are seeing. I make a gold chloride solution for my rubies and then mix it in gold sands. My friend john just pours the gold chloride into the batch,
There are three important things in the receiving batch, Gold , lead and selenium.

By livering, do you mean a colloidal solution is formed in the glass of gold and possibly silver nanoparticles/nanospheres? What do the lead and selenium have to do with the gold?

Pete VanderLaan 09-14-2017 07:46 AM

just to be clear. If you don't use lead and selenium in a ruby glass, at the best it will be weak in color but more likely to not strike at all. Tin is used in old formulas, I've used it but not without the prior mentioned materials.

Big molecules reflect light. Small molecules tend to allow transmissivity. You should melt a few pots of it and gain some real world understanding.


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