The Museum of Decorative Arts in Prague holds a unique collection of Bohemian double-walled glasses, silhouette portraits and reverse paintings on glass. Contrary to the generally-known folk-art reverse-glass painting practiced in the 19th century, these two-dimensional items were executed through the exacting technique of scratching away paints or gold leaf with a sharp-pointed stylus. From the Middle Ages, these images painted on the reverse side of sheet-glass panels or mountain crystal panes were used as devotional objects, incorporated in altars and frames, mounted as panes in sideboard furniture, or served simply as pictures. All these objects have one thing in common: given the use of organic substances — resins, fruit-tree gums, egg white and oils as binders, they are much more vulnerable to damage than hollow glass. Relentless time coupled by unsatisfactory storage has caused their current state of disrepair. Considered the most endangered museum treasures, these artefacts come under strict protection regulations, requiring proper storage and, in many cases, a conservator’s intervention.

The first opportunity to return the reverse-glass paintings their original appearance emerged in 2001, during the preparations for the exhibition “The Glory of the Baroque in Bohemia”, when two of the paintings were restored — “St. Wenceslas in Glory” and “Saint Wilgefortis”. The glass panels were restored by Eva Rydlová, the museum’s long-time external collaborator. Within the ISO programme (Integrated System of Movable Cultural Heritage Protection), funded by the Czech Ministry of Culture, the museum staff has been striving to ensure the gradual restoration, conservation and satisfactory storage of the reverse-glass paintings, double-walled glassware and silhouette portraits in a way that will prevent their further deterioration. Based on this programme, special glass cases have been fashioned for the keeping of both damaged and restored objects.

During the years 2003--2005, the state of all these glass objects was thoroughly inspected, the damaged objects were selected and a restoration work time schedule was established. The final report on the examination of the double-walled glasses and reverse-glass paintings included analyses of the materials applied, elaborated by ing. Ivana Kopecká of the preservation technology laboratory attached to the National Heritage Institute in Prague. For more on the subject, see: Eva Rydlová, with the technical assistance of Peter Drobny, Zwischengoldgläser from the Museum of Decorative Arts, Journal of Glass Studies 49, 2007, pp. 103—126. A total of 27 items have been restored since 2001, some of which are described hereunder:

The Entombment
Southern Tyrol or Venice, 2nd half 16th century
sheet glass, reverse painting in covering paints, dimensions: 24 x 19.5 cm, with frame 31 x 26 cm
Inv. No. 18.188, donated in 1932 by Gustav E. Pazaurek

Lamentation over the Dead Christ / The Nativity
Tyrol, 2nd half 16th century
sheet glass, reverse painting in covering and transparent paints, dimensions: 12.5 x 27 cm, with frame 26.5 x 31.5 cm
Inv. No. 3.586, donated in 1890 by Vojtěch Lanna

Drinkers in a Tavern
Gerhard Janssen (1636—1725), Vienna, dated 1698
sheet glass, painting in black and brown paints, gold leaf, inscribed IG 1698, dimensions 25.4 x 23.3 cm, with frame 34 x 31.5 cm
Inv. No. 9.369, donated in 1906 by Vojtěch Lanna

Psalm 30 from King David’s Book of Psalms
Southern Germany ?, late 17th century
sheet glass, painting in black and brown paints, gold leaf, gold and silver leaf, dimensions 18 x 26 cm, with frame (modern) 29 x 36.5 cm
Inv. No. 14.687, purchased in 1918 from Richard Preissler

Peasants at Table
workshop of Daniel and Ignatz Preissler
Kunštát in the Orlické Mountains, early 18th century
sheet glass, reverse painting in black paint, gold leaf, dimensions 23 x 16.7 cm, with frame 28.3 x 22 cm 
Inv. No. 10.377, donated in 1906 by Vojtěch Lanna

St. Wilgefortis
workshop of Daniel and Ignatz Preissler
Kunštát in the Orlické Mountains, early 18th century
sheet glass, reverse painting in black paint, gold leaf, dimensions 45 x 37 cm 
Inv. No. 14.784, purchased in 1918 in Prague

St. Wenceslas in Glory
workshop of Daniel and Ignatz Preissler
Kunštát in the Orlické Mountains, early 18th century
sheet glass, reverse painting in black paint, gold leaf, dimensions 42 x 35 cm 
Inv. No. 83.427, from the property of the Premonstratensian Monastery at Strahov

A Stag Hunt
workshop of Daniel and Ignatz Preissler
Kunštát in the Orlické Mountains, early 18th century
sheet glass, reverse painting in red paint, gold leaf, dimensions 37 x 46.3 cm 
Inv. No. 76.753, purchased in 1973 in Hradec Králové

Two Scenes from the Legend of the Old Testament Prophet Daniel
Franconia or Western Bohemia, 3rd third 18th century
sheet glass, black drawing, painting in covering paints and glazes, gold and silver leaf, modern frame, dimensions 25.5 x 33.4 cm, with frame 36 x 44 cm
Inv. Nos. 40.233—40.234, donated in 1955

Silhouette Portrait with a Musical Still-Life
Bohemia, c. 1790
sheet glass, painting in black paint, gold foil, dimensions 17.5 x 21.6 cm
Inv. No. 14.654, purchased in 1918 from the collection of Colonel Jan Novotný

Marbled Goblet
Bohemia, c. 1710
double-walled glass, cut, painting in bright colours, gold foil, height: 9.4 cm
Inv. No. 94.298, bequeathed in 1970 by Leon Bondy

Goblet Depicting St. Augustine
Bohemia, c. 1730—1740
double-walled glass, cut, gold foil, height: 9.4 cm
Inv. No. 13.198, donated in 1913 by Alois Potůček

Goblet Depicting a Boar Hunt
Bohemia, c. 1730—1740
double-walled glass, cut, painting in glaze paints, silver and gold foil, height: 8.2 cm
Inv. No. 13. 126, donated in 1913 by Alois Potůček

Goblet Featuring Symbols of the Seven Liberal Arts
Northern Bohemia, c. 1730—1740
double-walled glass, cut, gold foil, painting in glaze paints, height: 8.3 cm
Inv. No. 88.806, purchased in 1981
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