Ancient Roman glass is a broad and varied subject as it touches a number of aspects of ancient Roman society, such as the impact it had on the Roman economy, on the ability to preserve or contain foods, or to make window pains and decorative artefacts.
Pliny’s Natural History (Book XXXVI, LXV) relates the legend that it was the Phoenicians who discovered glass: merchants with a shipload of saltpetre were preparing supper on a beach; lacking anything to support the pot over the fire they used blocks of saltpetre which heated by the fire and being in contact with the sand produced rivulets of glass.
“fama est adpulsa nave mercatorum nitri, cum sparsi per litus epulas pararent nec esset cortinis attollendis lapidum occasio, glaebas nitri e nave subdidisse, quibus accensis, permixta harena litoris, tralucentes novi liquores fluxisse rivos, et hanc fuisse originem vitri.”
Glass making techniques date back to the 3rd millennium BC in the Middle Eastern regions of Egypt and Palestine. The artefacts produced were ornamental: small, relatively unrefined yet colourful. These techniques were gradually refined and progressed through to casting of glass and cold-cutting of cast blanks. Sites such as Alexandria were particularly famous for their glass trade right through to the Roman conquest and later.
Real innovation came with glass blowing around the 1st century BC, at about the time of the Roman conquest of the Middle East and Egypt. This new technique enabled a greater speed and greater degree of artistic freedom and hence favoured and matched the demand for quality work of the Roman market – luxury glass could be mass produced.
From the C1st AD the growing Roman market and the personal wealth of upper strata of Roman society spurred glass production and techniques in many ways, be it with utilitarian purposes or as artefacts which could be shown off. It was soon realised that glass could also be used to mimic more expensive materials such as metal vessels, rock crystal and murrina (fluorspar) from which the most precious wine drinking cups would be made.
In some ways Rome is also to be credited with the ongoing knowledge of glass techniques to this day: after the fall of Rome these techniques might have been forgotten were it not for the enduring knowledge held in what remained of the Roman empire in the East at Constantinople. Glass blowing techniques were maintained there and eventually re-learned by the Venetians towards the thirteenth century and brought back to Europe. Venetian glass remains famous to this day.
Glass techniques in ancient Rome
The increasingly wide spread and uses of glass in its various shapes and forms also meant a spreading variety of techniques in its workmanship and production – the effects of a market driven economy and “supply and demand” mechanisms supported by the broadening spread of trade routes, commerce and information across the empire.
One of the most ancient, pre-Roman techniques of decoration was cutting and engraving. Clearly this was a generally slow process, open to irreparable error and by and large limited to one-off pieces of very personal style. Cutting would be done with a stone wheel in much the same way as was employed for the later luxury of cameo glass. Cut glass was a versatile technique which lasted throughout the rise and fall of Rome.
Mould Blown Glass
A further advancement on glass blowing was blowing into a cast or mould. This technique spread quickly during the first century AD, most likely during the reign of Emperor Tiberius. it is likely to have been first developed in the Eastern regions of the Roman empire, for example around Egypt or Palestine.
It involved a mould made in several sections which once cast could be taken apart and the raw piece extracted to be smoothed and finished. Clearly this easy method of producing relatively complex shapes in a repeated fashion meant not only that a production facility could be easily set up but also that it could easily produce a relatively good volume of wares to sell into the market.
Mould blowing is particularly interesting because of its impact in terms of the Roman market economy: the ability to produce a flexible variety of shapes had great economic implications. Moulds could be easily made and exchanged between glass blowing facilities. It also appears that the styles of mould blown glass ware which became most widespread and inter-regional were the most luxurious ones. Pliny (NH Bk 36.196) relates how emperor Tiberius tried to repress the recent invention of a particularly flexible type of glass (vitrum flexile) which mould blown was extremely similar to more traditional metal vessels and thus might affect the trade of such precious metals.
“ferunt Tiberio principe excogitato vitri temperamento, ut flexile esset, totam officinam artificis eius abolitam, ne aeris, argenti, auri metallis pretia detraherentur, eaque fama crebrior diu quam certior fuit.”
An example of this is the wonderful “cameo glass” where a gob of glass of a colour such as dark blue would be blown into a small bubble, placed inside a vat of molten opaque white glass (which re-softens the blue) and then the two would be blown into the shape required together. Once cooled the white outer casing would be cut with a stone wheel (and grinding paste) and carved with a hard metal scribe. The artist thus allows the inner darker colour to show through where required and using the white outer glass to show figures and images in relief.
Roman artisans were particularly skilled in this technique and what is particularly interesting to note, is not only the wonderful work they produced but also how it testified the effects of supply and demand: glass was used to produce relatively cheaply what had hitherto been done in more expensive and rather more difficult materials such as stone or shell. Glass was more versatile. You could literally order the size, colour and thickness of the artefact you wanted. It was hence both a popular as well as luxurious item towards the end of the 1st century BC and the 1stCentury AD.
Mosaic glass was another decorative technique applied to a variety of vessel shapes. Popular in the Greek world and even more so in the Roman. In this technique, coloured beads (aka “Murrini”), which could themselves be patterened, would be placed next to one another on a tray, heated to form a large solid lamina like a mosaic pancake. Taken out and cooled, a rim of molten glass would be placed round the edge of the disk and then the whole disk would be placed on top of a “slumping” mould and put back into the furnace for re-heating. On heating up, the disk would flow down the mould (thanks to gravity) and take the shape of the mould eg a cup.
Applied glass involved a blown glass shape to which a gob of glass would then be applied and drawn across to make trails and threads. Similar to this and perhaps simpler is Blobbed or Speckled Glass. This was a simple and widely employed type of decoration across the Roman empire, particularly from the third century AD. In this technique glass blobs or specks of uniform or different colours were applied to the blown glass shape and then reheated so that they fuse to the body.
Rather like cameo glass in concept except for the fact that the inner and outer skins are held separate by tiny bridges which hold them together. Rather like having the cameo relief almost free-standing from the cup’s main body which holds the liquid. A number of these cage cups survive to this day and command amazing prices at auction.
Painting glass was another oriental innovation which found its way onto the Roman market place by the 1st century AD. The technique was very ancient but particularly enhanced by the glass blowing technique. The colours would be painted onto the new object and then re-fired so as to bind them permanently. This generated a rather more versatile , luminous and detailed effect than cameo (not to say that Cameo wasn’t more “beautiful”!).
Gold leaf and Portraiture
To the sphere of roman painted glass we might add “portraiture” which in some cases appears to be near photographic in quality. The effect was achieved by applying a gold lamina to a glass medallion, usually of blue transparent glass. The gold leaf could then be worked by pin-pricking it to give an image and a second piece of glass fused to the back in order to seal it in. The function of glass in this case is as a painterly support rather than a utilitarian object in its own right although there were also a number of pieces evidently created to be an item such as a cup: the portrait of the person or couple would thus have been fused into the bottom of a cup, for example for some sort of commemoration or as a wedding gift and only later have been cut out and used as a seal for example in burials. An example of this work from Rome’s National Archaeological Museum (portrait of Gaius Cilnius Maecenas) is particularly well preserved.
The toga of the sitter has been rendered using a silver rather than gold leaf in order to suit the colour and texture of the clothing in contrast to the gold used for the portrait of the head.
The rendering of “chiaroscuro” (shading) is achieved by pricking away fine dots of gold leaf. Some colour, eg tempera technique, was then applied to achieve greater effect. A gob of very transparent glass would then have been poured on top and ground down to fine perfection with few (if any) air bubbles.
The technique was developed around the 1st and 2nd centuries AD, possibly in Alexandria, although it became particularly popular (yet always elitist) in the 3rd century AD. Examples of this technique have been found in catacombs such as the catacombs of Panfilo.
Portraiture on glass wasn’t always using the gold leaf technique, a particularly fine example of colour portrait applied directly to glass has been found at Pompeii and dates to the first century AD (ie about the time of the eruption). The artefact found at Pompeii was coloured and re-fired but doesn’t have a protective glass coating which makes it particularly vulnerable, perhaps it was part of a pair, rather like a locket. The technique is very much akin to similar work produced at Alexandria – only a century later did it find its way to local Campanian workshops.
The portrait is three-quarters view and of extremely good painterly technique with fine brushstrokes following the planes of the image being painted thus giving a strong sense of “plasticity”. Worthy of comparison with 18th and 19th century miniature portraits in terms of skill and realism achieved.
It’s worth having a look at this great video of different Roman glass objects of all shapes and colours!
Further information is available regarding ancient roman pottery and about Ancient Roman drinking cups