A complex artform

Reverse glass paintings are very delicate objects. This portrait of a young girl shows some of the typical damage that can occur to these types of works: the glass has become dirty and the paint has come loose from the glass in places. Around 15% of the paint has been lost entirely. The glass pane has been broken into four shards. To secure the shards, a strip of adhesive tape has been attached to the paint.

Considerable damage has been caused by trying to secure the shards using the adhesive tape. The adhesive tape was attached directly onto the paint on the reverse and, in some places, has become stuck fast to the colors. Even after carefully removing the adhesive strips, the restorer could not prevent the paint from coming loose from the glass pane and remaining attached to the adhesive tape.

After removing the adhesive strips, the paint was strengthened and any loose particles were reattached to the glass. The broken shards were glued together. Where possible, the restorer removed the paint from the adhesive strips and fixed it back to the glass. In places, imperfections were retouched. The picture was backed with handmade grayish-brown paper which seals the imperfections as best possible.

This perpetual calendar has been in the Kaufbeuren Town Museum's collection since its early days. Prior to restoration, it was seriously damaged: the broken shards glued together in previous restoration measures had broken again. There were many imperfections in the glass. The paint had come away from the glass in places, and in some cases had attached itself to the backing cardboard which was highly acidic. The sheet metal plating had been lost in places.

As part of the museum's refurbishment, many items were restored including this reverse glass-painted calendar. To start with, the individual broken shards were detached and the broken edges cleaned. They were then re-attached to each other using an epoxy resin, and the small imperfections and cracks filled in using a UV adhesive. While being glued back together, the shards were held in place with small adhesive strips on the glass side.

On the back of a reverse glass painting, you find the final applications of paint that make up the larger areas of color. The painter always paints the details and fine work on the pane of glass first, and then adds the paint to areas increasing in size, so that the rear side of a reverse glass painting reveals a fairly crude color application.

Once the paint that has become detached from the glass has been refixed using microcrystal wax, the monocolor sections are retouched using tempered oil paints. In areas where additions would have to have been interpreted, the imperfections were left and sealed by placing a cardboard retouch behind the glass. For this purpose, the areas behind the imperfections were finished using gouache paints in the corresponding color on age-resistant museum card.

Following the restoration, the perpetual calendar gleams with a new radiance: cleaned, restuck, secured, and retouched, the reverse glass painting looks fresh and new.

This reverse glass painting was purchased in 2013 from an antiques dealer. It displayed typical damage for a reverse glass painting, and the glass pane was dirty on both the glass and paint sides. Almost half of the paint had come loose from the glass, and up to a fifth had disappeared entirely. The painting was severely damaged, with blisters and slices of paint having come loose from the glass and some paint particles having slipped out of place.

After removing the frame from the reverse glass painting, the imperfections can be seen even more clearly. A lot of paint has been lost from the blue sky and the brown tree trunks. The mountains in the background behind the fortified town have almost completely flaked off.

In some places, the paint has come loose from the glass in strips until it has completely flaked off. If the reverse glass painting has been sealed with a wooden backing board, the loose color particles tend not to be completely lost, but often do not stay in place. Larger fragments can, in the best cases, be refixed in their original position. Paint that has come loose from underneath in slabs can be reattached carefully to the glass using microcrystalline wax.

The imperfections in this reverse glass painting have been backed by acid-free card in a matching color. This means that gaps can be visually sealed without new elements being added by retouching with paint and thus creating a false impression of the picture.