Topic: Exploding glassmaking myths - Roman Diatreta or Cage Cups

[Frank]

As mentioned in a earlier thread here is the link to how diatreta or cage cups were made. For years it has been accepted that these were made by carving a solid thick walled blank.

http://www.rosemarie-lierke.de/English/Cage_Cups/cage_cups.html

see also http://www.pressglas-korrespondenz.de/aktuelles/pdf/pk-2004-1w-lierke-diatrete.pdf for lots of images with German text

For the myth (Or is it  :? ) here is a link at Corning Museum of Glass

http://www.cmog.org/index.asp?pageId=756 note that they state this was decided in the 1960's.

There was also a reproduction made in the 70's or 80's by a Scottish glass artist I will try and find that link too. He used the casting method as too, have several others who have made cage cups since.  I suppose the next stage will be to scan an original in 3D produce a metal or plastic copy on a 3D printer and use that to create a mould. The you will get an almost indistinguishable copy of the real thing :wink:

The methods used by Barry Sautner http://selman.com/sautner.html are very different but he uses more recent sand-blasting technology,

July 23, 2004
Roman Glass Bowl Sets World Record in London

An extraordinary and fragile Roman glass bowl, dating from circa A.D. 300, broke the world record price for a piece of glass sold at auction July 14th in London. Selling to a telephone bidder at Bonhams' Sale of Highly Important Antiquities, The Constable-Maxwell Cage-Cup fetched £2,646,650. It was once used as a lamp and had been carved from a solid piece of glass.

Following the sale, Joanna van der Lande, head of antiquities at Bonhams, said: "The Cage-Cup is exceptionally fragile, cut from a single block of glass. It would have been clear but has become iridescent due to a reaction between the earth it was buried in and the glass. Its probable use was as an oil lamp suspended by a collar around the rim. It's really a very highly prized piece."

The cup was last sold in 1997 as part of a collection formed for investment purposes by the British Rail Pension Fund. At that time, the cup sold for £2,311,500.

[KevinH]

Thank's for the details and the links, Frank.

I am now having recollections of reading something before about the "questions put to a proponent of the cutting theory". I had forgotten about that. Most of what is said in Rosemarie Lierke's 2004 webpage article makes good sense to me. I can therefore accept the "two-shelled blank" explanation. The parts that I don't quite follow are probably because I don't properly appreciate how the outer wall network was formed in order for parts to be removed at the correct positions.

But even if the two-shelled approach was the method used by the Romans, it still seems clear that the outer cage and the support struts were finished by cutting, including some possible undercutting.

In the thread on "Paperweights" my analogy to the Chinese "balls-in-balls" can now be said "not to hold water" (both figuratively and physically   ). And yes, the actual technique used for Barry Sautners's work is somewhat different.

What I still find intriguing, though, is the (apparent or real) lack of acceptance by some authorities of anything but the "cut thick-wall" process. I assume this is the reason for Bonhams blurb to stick to the long-standing line. And it perhaps also explains why the Glass Cone article, which was based on much of the Bonhams commentary, and focussing on the "cup vs lamp" idea, gave no alternative views on the procedure.

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If anyone gets a chance to visit the Glass Musem at Jelenia Gora in Poland, they have a very nice example of a modern reproduction of a "cage cup", but unfortunately I did not get any information on it when I was there.

[Frank]

What I still find intriguing, though, is the (apparent or real) lack of acceptance by some authorities of anything but the "cut thick-wall" process.

What is missing here is the discussion that set the cut thick-wall process. If anyone can track that down at least we can see details of both arguments.

It is not uncommon in Academia for theories to persist despite later eveidence. This is often caused by conservatism rejecting the new kid on the block versus the aged and respected professor of the original concept (general terms, not specific to this case) particularly in anything 'scientific'.

At another level, they are both theories and could be completely wrong.

Certainly for an auction house there is more more marketing value in some guy spending twenty years scratching away the the glass with a small diamond on the end of a stick, than knocked out in a mould. It is a question of awe :shock:

If you read all of the material you will find that these cage cups were expensive but not rare items in Roman times. Probably much cheaper than the equivalents today in relative terms. Some fifty whole or partial cage cups have survived.

[Frank]

Incomplete discussion :?:  :?:  :?: Polish data, German info

[aa]

http://www.cmog.org/collection/detail.php?t=objects&type=browse&f=maker&s=Scott%2C+George+D.&record=0

[Div]

Dear Frank,
there's no doubt whatsoever that late Roman cage cups WERE carved from thick glass blanks. Lierke's preposterous idea that they are made by squeezing hot glass through a colander-like mould of plaster is absolutely risible, like most of her impractical theories. If you can, do try and  examine one of the Roman originals up close, and you will clearly see the marks of grinding and polishing wheels where they have carefully carved away the walls, leaving the cage supposrted on the glass pegs. I'm afraid it's definitely all one piece of glass. I have examined many originals, and there are several of us in the world who actually MAKE cage cups for a living - we'll all tell you the same thing!

[Frank]

Who are you ?

I don't usually look in this forum, it is Angela's Scottish forum, my forums moved to Scotland's Glass - not sure why this Roman topic is in here though the Scots kept the Romans out.

[aa]

Probably here because of this:

There was also a reproduction made in the 70's or 80's by a Scottish glass artist I will try and find that link too. He used the casting method as too, have several others who have made cage cups since.  I suppose the next stage will be to scan an original in 3D produce a metal or plastic copy on a 3D printer and use that to create a mould. The you will get an almost indistinguishable copy of the real thing :wink:

George D Scott. see link in to Corning above.
 

[Div]

Dear Frank,
I'm afraid I don't know why this topic's on the Scottish Glass page either! I found the reference by typing in 'cage cup', to see if anyone was discussing diatretus work, and replied to you post!
I'm David Hill - one half of Roman Glassmakers (www.romanglasmakers.co.uk) We specialise in researching and reproducing glass from early periods, and we've recently begun working on cage cups, and the related series of 'diatretus' vessels. Cage cups have always excited folks' imagination because it's hard to accept that anyone can have the patience to create a vessel with an attached 'exo-skeleton' by carving from a thick blank, but believe me, there are very few shortcuts, and they're certainly not made by the 'plunger and colander mould' method that has been suggested elsewhere! The late George Scott (of Edinburgh) made his excellent reproductions using small copper wheels and different grades of abrasives, with a direct drive machine, whereas I use a Merker glass lathe, copper, stone and many other wheels, as well as other tools, including much hand finishing. Attached is a picture of me working on a reproduction of the Munich cage cup. As you can see from the piccie, these vessels are not as big as the impression one often gets from pictures in books. Apart from two notable whoppers, the Hohenzuelzen bowl (destroyed 1945) and the so-called 'Constable Maxwell cup', most of the surviving examples are not much bigger than large coffee cups. Although they do take a time to carve, they are very satisfying to create - precisely because of, not despite, their difficulty! Best wishes,

David

[Anne]

As this is more general GLASS than Scottish Glass I'll move it over to the proper place.