Topic: Ferro & Lazzarini ?

[chopin-liszt]

Oxidation of copper is different to the metal reacting with the glass itself.

I don't know if copper does - but I do know silver does - hence yellows and ochres from the silver (in silver chloride) with clear glass and greens with blue glass. Silver (from the nitrate) will react with red glass to produce browns. You also find that lovely ethereal blue cloudy effect deep within a thick casing.

Copper oxide is black, a chemical substance on its own.

I did think copper should react directly with the metal, because of what Ed told me about using copper wire to give his colours.....
However this is all physical chemistry, I'm far more comfortable with the organic sides of science.

[rosieposie]

Hi Christine,  your 'wiki link' describes perfectly what I was trying (rather clumsily) to describe about how goldstone was produced.....thanks, it is a great help to me as well as anyone else reading this thread. 
I am now convinced it is the waste or spoiled pieces used for the weight!!

[Lustrousstone]

Sue It's not the same; silver chloride is a compound that decomposes with heat to form silver and chlorine. Silver and chlorine are both way more reactive than copper, which is really pretty stable. These probably react with constituents in the glass other than the silica to give your colours

[chopin-liszt]

The chlorine dissipates as a gas..... when it's silver chloride, and both copper and silver tarnish in air (the green "copper" you see on roofs (rooves ) is copper nitrate.
When you heat copper in just a bunsen burner, it goes purply and dull and red and sort of multicoloured - I've done copper enamelling, (jewellery, by myself) and I've seen fused glass plates and dishes with copper inclusions - which are all "burnt coppery" colours (they're lovely pieces - The Carnelian Gallery, in Crieff  )  and glass is fused at lower temperatures than are required to melt glass....
 
(
I did say I'm no good at physical chemistry.... I've just got a few inklings about how individual ions work, and they've got a nasty habit of flying off at random in subatomic bits.
I like great hulking lumps of protein molecules swimming around in a pH specific primordial soup, doing lovely neat gloopy enzymatic things with other proteins in a controlled manner at controlled rates..... mump grump... )

[Sach]

Copper does indeed cause pigmentation of glass.  It is used to produce shades of blue, green, and red depending upon the other elements present in the batch, the relative percentages of those other components, and the level of oxidation/reduction produced in the melt.  For aventurine it is necessary to control the conditions to prevent this from occurring and to induce the copper to crystallize out of the glass "solution".  Overheat your aventurine as you work it and the resulting color is a pinkish beige without any sparkle.

[chopin-liszt]

I was sure it must,
thank-you, Sach. I was doubting my sanity.
( no comment please, Christine!  )

[Lustrousstone]

Sach is right of course

The colours will only form (i.e., the chemical reactions) when the conditions are right, which generally means in the presence of "oxygen", water or some other catalyst; heat is not always enough. Once the batch of raw ingredients has formed glass, everything that is going to react will have reacted and you have a pretty inert medium. That is why you can put silver metal, gold metal and copper metal into glass and they stay metallic. Silver chloride is an exception because it only needs heat to decompose. The chlorine is reactive enough to react with "whatever" in the glass and form a new coloured compound. The silver probably stays as silver metal but because there is so little of it you only see it when it is on the surface, as iridescence. Iridescent treatments rely on the fact that a spray containing a reactive salt and, importantly, lots of air gets hot on the glass surface. That the "colour" is sticks is more physical at the molecular level than chemical.

[chopin-liszt]

I really don't think chlorine reacts with molten glass. It will form a gas and escape or form bubbles.
It's just the silver that reacts, to give the colour.
Most dyes and colours are associated with metals - (apart, I suppose, from the modern synthetic ones - I'ne notaclu what are in them.

[ck2407]

Still unsure about this paperweight 

The 'rocks'/'sand' on the base of the weight are very sparkly and more gold in colour than copper in reality.  The glass itself is transparent and only has a very few tiny bubbles in the 'dome'.

The signature on the base is ferro murano? and although it's quite clear it is ornate/old fashioned?

Does anyone know anything about this company/paperweight? (I've attached 3 photos)

[Sach]

Just opened this thread and quickly glanced at the image.  Read the first word as "Mexico", I can still see it that way just as easily as I can "Ferrro"   The use of copper aventurine does suggest Murano, although I would expect them to use it much more effectively.