unknown, bowl, 1700 - 1800

8.4 × 13.7 × 13.2 cm, 921 (KN&V)
COLLECTION Museum Boijmans Van Beuningen. Bequest of Dr E. van Rijckevorsel.
PHOTO The Visual Art Box, 2025

creation

making process

Material colourless and coloured clear glass
Technique à la façon de Venise
Hot working free blown, with blown coloured elements and handles applied. Blown on the blowpipe, transferred to a pontil, then opened up and shaped by hand

• making techniques unknown maker, bowl, 1700 - 1800

The ovoid central blue element is ribbed on the outside. Such ribs are formed when a glassmaker slowly blows a glass bubble into a mould. The ribbing on the central blue element enhances its visual effect when the object is used.

(art) history

It is very likely that the object was used in the past and was also probably cleaned and dried. No information survives about its earlier history, so nothing is known about its previous use or storage conditions.

Glass expert Kitty Laméris and glassmaker Marc Barreda recreated Venetian glasses in an attempt to identify their intended uses. They also made a glass with a large blue glass sphere, based on a historical object. Its purpose remained unclear until they poured champagne into it. The blue element suppressed the rising bubbles, probably to prevent the champagne from spilling over. It also gives the entire bowl a cerulean appearance, which looks spectacular.

conservation

research & diagnosis

technical analysis

visual examination

b.1 scratches or abrasion, b.2 cracks, b.4 lacuna(e), b.5 dust, dirt or stains, c.1 cloudy appearance, c.2 slippery surface, d.1.1 deposits: droplets, d.2.2 crizzling – full blown.
The object is not physically numbered.

Thin walls, lacuna around the base of the handles, pieces of the handles missing. Large cracks, (micro)cracks.

IC analysis of ion concentrations on the surface

IC shows high concentrations of ions on the surface, particularly sodium cations and formate anions. Potassium cations and acetate anions were also detected.

• IC Form

pXRF analysis of the composition

The analysis shows a mixed alkali–lime composition. The instability of this glass may be causally linked to the low lime content or to the presence of manganese.

• XRF Form

Previous treatments

The object was probably cleaned with demineralised water in 2013. The archives contain references both to the fact that it must not be cleaned and to the fact that it may only be cleaned to a limited extent.

Condition diagnosis

Condition (visual) poor
Condition (IC) likely unstable

(click on photos to enlarge)

advice & treatment

Suggestions for packaging, handling, storage and transport

Advice: record the vulnerabilities of this object in the (museum) documentation system and/or at the relevant location in the (museum) storage facility.

Because of its extremely fragile condition (see research & diagnosis: likely unstable – thin-walled – cracks and lacunae), the object must be handled as little as possible and with extreme care. It should therefore be placed in such a way that it can be moved and handled without direct contact with the object.

In such situations, care must be taken to ensure that there is as little contact as possible between packaging materials and the glass (packaging materials may absorb droplets and create a microclimate that is not conducive to the conservation of the unstable glass object). If the object must be handled, bear in mind that it is slippery because of the droplets on the glass surface. Take particular care when wearing nitrile gloves.
Also bear in mind that the object is badly broken and has lacunae around the handles. Never handle the object by the handles. Lift it with both hands and provide adequate support. Place the object in a portable container and handle it only when absolutely necessary. Keep the object in a separate cabinet with other unstable glass. Ensure the object is positioned so that its condition can be easily monitored and that it is readily accessible for inspection.

Suggestions for monitoring the environment and climate

Place the object in a stable environment with minimal fluctuations in relative humidity and temperature. It is highly advisable to monitor both the condition of the object and the climatic conditions regularly to detect changes at an early stage and to analyse any links with the environmental conditions. The object cannot be loaned.

Suggestions for treatment

Research shows that the object’s condition is deteriorating. Following a past cleaning treatment, ion concentrations on the glass surface have begun to rise again. This deterioration is currently being studied to devise specific cleaning strategies.
Cleaning the object is advisable because droplets on the surface contribute to further degradation.

Only a glass conservator can determine whether cleaning is desirable and feasible, which cleaning method to use and how to closely monitor the condition. If undertaken, only a glass conservator should clean the glass.

Suggestions for further research

Further research into glass instability, particularly in relation to cleaning, and into the storage of unstable glass is urgently needed.