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Panel in the Stile of Rococo, End of 18th Century
Introduction

Dimensions:

60 cm in height, 90cm in width, 34 in length on a longest part
Final facing:
Parcel water silvered, parcel water gilded, parcel imitation of gilding
Type of treatment:
Restoration
Storage and display:
Private collection, for everyday use


Condition

This Object was found left over in the old building cellar. Whole surface was embedded with surface dirt.
Due to fact that the object spent long period of time under the influence of increased humidity ornaments made of traditional stucco cracked and parts of them delaminated. On the end of the lags traditional gesso completely delaminated under the influence of moisture.
Condition of wooden body was very good probable owing to thick layer of ground applied on the all inside surfaces. There was not any trace of fungi or pest contamination. In constructional sense condition was also very good. Construction was firm although cracks were present between back and side rails joined by mortise and tenor. Small corner block on the right was missing (fig.1. & fig.2.).

Technical Analysis

Prior to restoration work the following analysis were performed:

Analysis of Materials and Techniques Involved

The body of the object was made of Beechwood (Fagus sp.). Ornaments were made of traditional stucco supported with iron armature which completely oxidized and lost quality. Object surface was cowered with traditional gesso 2 to 3 mm thick, (calcium carbonate powder and organic adhesive probable Fish-eye glue). Ornaments were covered with layer of dark red bole then gilded and silvered by water gilding technique (fig.3.). Other were decorated with imitation of gilding probable using alloy foil and oil size technique. Inside surfaces were treated with traditional carpenters ground.

Identification of Cowers on the All Parts of Object

The layer of cower on the surface of object was the oily, dark substance accumulated trough the time (fig.2.).

fig.1. click on to zoom
fig.2. click on to zoom

Choice of Treatment

Treatment on this object was performed in two phases:

Phase I: Choice of Cleaning Treatment

Selection of Solvents for Cower on the All Parts of Object

Test for dissolution of cower was performed on the samples taken from the surface of the object. Tested solvent was the admixture of methylen chloride, methanol, cellulose powder and paraffin oil with addition of tenzids.
Dissolved substance was rinsed with 96-99% ethyl alcohol. After the process gesso, water gilding and silvering on it stayed undamaged.

Cleaning Process

Tested solvent was gradually applied. After few minutes stimulated, left to react for few minutes and stimulated again. After 30 minutes dissolved substance was rinsed. On some areas process was repeated due to very thick layer of oil size and oil size ground.
Object was left for few ours to dray (fig.3.) and then test with drop of water was performed to determine ability of porous. Result of test was good so it was decided not to repeat cleaning process.

fig.3. click on to zoom

Phase II: Choice of Restoration Treatments

Selection of the Materials and Procedures for Crack Recovering

For recovery of cracks in traditional stucco test was made with admixture of powdered gypsum (CaSo4), kaolin and PVAC resin. Prior to application of admixture crack was moistened with 15% etil alcohol to assure good contact of admixture and wood. Solidification time was about 15 minutes. Sample was left to dray for 12 hours. Test resulted with solid, consolidation backfill.

Selection of the Materials and Procedures for Consolidation and Recovering of Original Gesso

Due to good experience with admixture tested on cracks, it was tested for filling of areas where the parts of original gesso delaminated. Area was prepared with 15% ethyl alcohol as the crack in previous test. Admixture was pushed into and flattened with moistened spatula. The result was satisfactory.
In order to consolidate the numerous small cracks in original gesso, make better contact within original gesso and new fill and make solid ground for new gesso the 'contact ground' was tested. Request was to obtain surface solid enough to resist pressure during the polishing of gold and silver and porous to except new gesso. The ground was composed of calcium carbonate, in form of fine powder (Bologna chock), zinc oxide powder and PVAC resin. By the and of mixing 90% izo propil alcohol was added to improve leaving of captured air. To make it applicable with brush admixture was diluted with distilled water. Surface was coated 3 times with time delay of 15 minutes to provide solidification time for each layer. Sample was left to dray for 12 hours. The result was solid but porous surface, enough resistible on pressure preventing the original gesso from delaminating.

Restoration Process

Two curve shaped corner blocks were mounted in the back corners of construction. They were made of Pinewood (Pinus nigra) and fixed with four 3 cm long screws and aliphatic resin glue (1). Delaminated parts of ornaments made of traditional stucco were affixed with help of admixture tested for cracks. Missing parts of ornaments were made by sculpturing and with help of shapers made of hard rubber used for the reef elements along the legs and rails and for the batten on the top of the rails. Before sculpturing new armature made of protected copper was placed and fixed with admixture tested for cracks. Support for reef elements and batten was made by application of 3 cm long steel nails along the reef and batten area. They were connected with protected copper streak. Reef elements were made in one pass. Batten was made in two passes, by application of half of material, then burlap and then second half of material to make it stronger and prevent from cracking during the drying period (fig.4.). Some ornaments were copied by the help of silicon mold.
Material used for sculpturing and coping was model plaster (2) with addition of PVAC resin.
Drying period was 12 ours.

Tested admixture was applied on cracks and flattened by moistened spatula. Priors to application cracks were moistened with 15% ethyl alcohol.
Delaminated pieces of gesso and carbonized substance was removed mechanically. Previously tested procedure was applied now. After 12 ours of drying areas of intervention were shaped by the help of turbine.
Prior to application of the 'contact ground' whole surface of object was cleaned whit 96% etil alcohol. The 'contact ground' was applied in three layers as it was tested and then it was left to dray for 2 hours. New traditional gesso consists of technical whiting (CaCo3), zinc whiting (ZnO2) and rabbit skin glue was applied shortly afterwards in four layers. Every layer was left to solidificate for 15 minutes. The ground and the new gesso was applied only on surfaces planed for water gilding and silvering and on surfaces where the procedure with admixture was applied.
After 12 ours surfaces of object was shaped with sandpaper. In order to prepare flat and smooth surface important for quality of water gilding sanded surface was colored with ocher bole and sanded again with 4 grades of sandpaper. During the sending surface was rinsed with mineral spirit. Next 12 ours object was left to dray.
Bole (3) mixed with 5% rabbit skin glue was partially applied in 6 layers and then gilding and silvering was performed by water gilding technique. After 12 our gilded and silvered surfaces were burnished (fig.5.).
On the surfaces planed for imitation of gilding, prefabricated nitro ground (4) was applied in 3 layers. After 30 minutes of drying one coat of synthetic oil size (5) colored with dark red neutral pigment (6) was applied. Imitation was finished with Dutch metal leafs.
Toning was carried out with 'bitumen from Judea' (7) mixed with turpentine and Damar lacquer.
Due to fact that this object will be exposed to the circumstances of everyday use, final protection was carried out with Zapon lacquer (8) thinned with acetone (propanone). The inside area of the object was treated with prefabricated carpenters ground (9) to prevent it from possible cracking.

fig.4. click on to zoom fig.5. click on to zoom
fig.6. click on to zoom
List Of Used Prefabricated Materials

1. Aliphatic resin glue: Titebond wood glue , Franklin International , USA
2. Model plaster: Krone Hiliges Gipswerk, Germany
3. Bole: Red, Lefranc & Bourgeois France
4. Nitro ground: Duga, Yugoslavia
5. Synthetic oil size: Goldanlegeol - Mixtion, Lukas, Germany
6. Dark red neutral pigment: Lefranc & Bourgeois France
7. Bitumen from Judeja: Liberon , France
8. Zapon lacquer: Liberon , France
9. Carpenters ground: Duga, Yugoslavia

Applied Gold, Silver and Metal Leafs

Gold leafs: Orange Doppel Gold, 22 Karat, Noris, Germany
Silver leafs: Blattssilber Normal, Noris, Germany
Dutch metal: Noris, Germany