Topic: Complex Opalescent Cased Vase w/ Hollow Base.

[chopin-liszt]

You're not talking to yourself, I'm paying attention! When you say it's more opalescent than iridescent, is it on or in the inside glass? (ie has it been applied in some way?)
Wish I could get my mitts on it to study it properly!

[Pinkspoons]

It's on the surface of the glass, on the interior of the vase, and terminates at the rim - so presumably it's a localised heat-treatment.

It's a difficult one to describe because it has so many things going on, despite its simple appearance.  

[Cathy B]

It's on the surface of the glass, on the interior of the vase, and terminates at the rim - so presumably it's a localised heat-treatment.

That's what looks like has been done. The brown you see when you hold it to the light is what they refer to as opalescent fire. It's quite lovely, imho.

[Pinkspoons]

Oops - I didn't realise that the red/brown was a byproduct of the opalescence process. Shows how much I know! 

So it's not cased glass at all... which is a little frustrating because I came on to say that I'd recently been shown some cased Cenedese vases, unsigned but bearing labels, that share a few characteristics with my vase.

I thought I might be one step closer to pinning down a maker - but perhaps not.

Might "Czech" be eliminated from the title, as I think it's become clear that this is quite unlikely.

Ta. 

[Mosquito]

I'm afraid I have to disagree a little with Cathy here; firstly the vase looks almost certainly to be cased - yes it could be a heat-struck opalescence but the distribution of the opacity and colour strongly suggest it to be cased, the combination of opalescent and clear/ coloured glass is by no means uncommon.

Secondly the brown colour has clearly been created intentionally by the addition of a colouring agent. Maybe we need a chemist here, I don't know what chemicals are used for brown, nor whether the graduation of the colour is also achieved by a heat transformation or not. Either way it's not solely the usual opalescent 'fire'. The 'fire' that people refer to is due to the optical characteristics of opalescent glass. Opalescent glass reflects white light (or more commonly an icy blue-white achieved by adding a trace of cobalt), and so appears whitish in most light. When backlit, however, the 'fire' shows, due to the fact that the glass transmits light towards the red end of the spectrum. Actually this 'fire' can vary from a pale yellow to a deep red depending on the intensity and composition of the opalescence.  Either way opalescence doesn't typically cause such a brownish 'fire'. Also if it was just the 'fire' that gave the brown tone then it wouldn't show at all on the outdoor grassy shot where the vase is transmitting relatively little light.

I don't want to sound too pedantic, but it's important to understand how this piece was made and avoid getting sidetracked. As to maker, I'm afraid I can't really help other than to say Italy seems most likely given the technique.

Steven

[Pinkspoons]

Thanks for clarifying the issue - I don't really have very much experience with opalescent glass of this kind.

There does seem to be some correlation, though, with the opalescence and the red/brown colour, as they both terminate at exactly the same point a little over halfway into the vase.

But it does indeed show much in the way of colour regardless of the angle/brightness of the light.

[Cathy B]

What I am seeing is some sort of applied black rim, an inner layer which is milky in normal light (Nic's third picture) and brown in his light box (Nic's pics 1 and 2), and then a clear casing. In Pic 3, you can see that the milky glass is on the inside as well as the outside.

Opalescent glass reflects white light (or more commonly an icy blue-white achieved by adding a trace of cobalt), and so appears whitish in most light. When backlit, however, the 'fire' shows, due to the fact that the glass transmits light towards the red end of the spectrum. Actually this 'fire' can vary from a pale yellow to a deep red depending on the intensity and composition of the opalescence.

I am assuming that when the pictures were taken in Nic's lightbox, the glasses appeared that brown colour, and that under normal light they are the milky colour. I have a trio of little birds which are milky white (with only a touch of fire) in normal light, but appear to be a brown very close to Nic's glass when backlit - I'll post photos soon.

[Pinkspoons]

The black rim is merely the shadow/refraction cast by the rim onto the opalescence (which stops just below the inside rim - visible in pic 3).

Under normal light it's still quite browny-red, as well as opalescent. But of the two, unless in very bright, direct, and shadowless daylight, the brown is the dominant colour. That said, it's hard to place the two as distinct layers. When viewed from the inside of the vase, it appears as though the opalescence is on the front and the brown is behind it, but this is also true when viewed from the other side, outside of the vase (if that makes sense?).

It's a hard one to photograph, because there's seemingly so much going on.

[Cathy B]

It's a very similar effect to my bird. Here are three pics under three different lighting conditions - standard fluoros, with a flash, and held up against the light to show the glow. There is some reddy-brown in the milky colour under some lights, but in sunlight it's mostly just blue. I was always under the impression this effect was what happened when the heat reactive glass was quite thick, but that may be wrong.

(Excuse Paul's dirty nails in the picture! It was a pain to show the effect.)

[Pinkspoons]

I see what you mean - the brown/opal relationship is very similar. As far as I can tell, the opalescent layer on mine is very thin indeed, so I'm not sure how they got such a depth of colour.

Nice bird, by the way!