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Cross Shape Frame in the Stile of Baroque, Beginning of 18th Century
Introduction

Dimensions:

118cm in height, 88cm in width, 7 cm on the thickest part
Final facing:
Parcel water silvered, parcel water gilded
Type of treatment:
Restoration
Storage and display:
Memorial museum collection


Condition

The object arrived in studio separated from the crown and side elements. The body of the frame (fig.1.) was cowed with thick layer of read and green pigment, oxidized bronze powder emulsion, and embedded with surface dirt. The crown and side elements (fig.2.) were also cowered with oxidized bronze powder emulsion and embedded with surface dirt.
Object was inoculated, and already damaged. The starting places of inoculation were, fortunately, elements that were used to hold crown and side elements (fig.3.), made of pinewood and they were completely destroyed. Inoculation progressed on the nearest parts of frame and crown end side elements, causing minor damages, except on the down side of the frame.
After small pressure applied on frame joints, they collapsed (fig.4.). They were adhered with very thick layer of bone glue.
Very delicate structure of crown and side elements was cracked. Only two of four side elements were present.
Parts of ornaments on the all parts of object missed.

Technical Analysis

Prior to restoration work the following analysis were performed:

Analysis of Materials and Techniques Involved

The body of frame was made of Pinewood (Pinus nigra). Crown, and side elements were made of Ashwood (Fraxinus sp.).
Frame ornaments wear made of Ashwood (Fraxinus sp.) by wood-carving and then adhered on frame. Crown and side elements were made by wood-carving too. All surfaces were covered with traditional gesso approximately 2mm thick, calcium carbonate powder and organic adhesive probable Fish-eye glue), and then with layer of ocher bole. Surface of frame was silvered and gilded by water gilding technique. Silvered areas were burnished but gilded ornaments were left non-burnished. Surfaces of crown and side elements were gilded also by water gilding technique. Some parts of ornaments were left non-burnished too (fig.5. & fig.6.).

Identification of Cowers on the All Parts of the Object

Surface of frame was cowered with layer of pigment in form of powder, mixed with inorganic binder. Side parts of frame were cowered with layer of bronze powder mixed with inorganic binder. Same bronze powder mixture was applied on crown and side elements (fig1. & fig.2.).

fig.2. click on to zoom
fig.1. click on to zoom
fig.3. click on to zoom
Choice of Treatment

Treatment on this object was performed in two phases:

Phase I: Pest Elimination Procedure and Choice of Cleaning Treatment

Pest Elimination Procedure

Due to possibility of active inoculation, fumigation procedure was applied. Object was exposed to carbon de sulfide (CS2) for 12 ours.

Selection of Solvents for Cower

Solvent test was performed with admixture which was already used in previous projects with very satisfying results. It was the admixture of methylen chloride, methanol, cellulose powder and paraffin oil. Evaporation time, due to presence of cellulose and paraffin was appreciably reduced, concentrating the reaction on cower. Admixture was applied on samples taken from all parts of object and after approximately 20 minutes of exposure, resulted in complete dissolution of pigment cower substance and bronze powder substance but only on the areas were surface was burnished. On the areas where surface was not burnished, dissolution of cower was partial. Thin part of cower was strongly attached, on microscopically rough surface. It was not possible to remove it by the help of solvent due to fact that particles of bronze powder in that case were not been attached on surface by means of inorganic binder.
After scaning and zooming, it was determined that particles of oxidized bronze powder were blended with particles of gold and bole. Only possible way to remove it was mechanical one but in that case, structure of object would be endangered. Consequences of that procedure would be only further damaging of object so it was decided not to proceed with mechanical cleaning.

Cleaning Process

Adopted solvent was gradually applied and after 20 minutes dissolved cower substance was rinsed with nitro-thinner (1). Object was left for few ours to dray. Condition after cleaning: fig.4. , fig.5. & fig.6..

fig.4. click on to zoom fig.5. click on to zoom fig.6. click on to zoom
Phase II: Choice of Restoration Treatments

Selection of the Materials and Procedures for Consolidation and Recovering of Areas Damaged by Pests

Due to good experience with admixture tested on all sorts of cracks in past projects, it was tested for filling of areas damaged by pests. Admixture was made of powdered gypsum (CaSo4), kaolin and PVAC resin. Area was mechanically cleaned of cutting dust and moistened with 15% ethyl alcohol. Admixture was applied in few layers. Sample was left to dray for 12 hours. Result was very firm, consolidating backfill.

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

In order to consolidate the cracks in original gesso, and make solid ground for new gesso the 'contact ground' was tested. Request was to obtain surface solid enough to resist pressure during the burnishing 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

Cracks in crown and side ornaments were consolidated by inlaying veneer peaces. Sides of cracks were mechanically flattened and then peaces of veneer were inlayed and adhered with aliphatic resin glue (2).
Veneer peaces and aliphatic resin glue (2) were also used to fill gap between mortise and tenor in rejoining process of frame structure. Gapes appeared after removing thick layer of bone glue. Bone glue was melted with beam of water steam and removed mechanically.
Some missing parts of ornaments were made by woodcarving and the other by sculpturing.
Parts of wood carved ornaments including two whole missing side elements were carved in ashwood (Fraxinus sp.). Parts of wood-carved ornaments were adhered with aliphatic resin glue (2) on appropriate places. They were supported with thin dowels specially made for each of them (fig.7.).
Smaller parts of ornaments that missed were made by sculpturing in Model plaster (3) with addition of PVAC resin. Support for them was made of protected copper streak.
Missing part of inside batten on the very frame was made of model plaster and PVAC resin, with help of silicon mold. First, thin plate (2mm) made of ashwood was affixed and adhered with aliphatic resin glue on the place of missing batten and then, ornament made in mold was adhered on it. Ornament was very thin, about 2mm in order to correspond, adhered on wooden plate, to other parts of the batten (fig.8.).
For recovering of the damages caused by pest, tested admixture was applied on all damaged places in corresponding amount. Damaged places were mechanically cleaned of cutting dust and moistened with 15% Ethyl alcohol. Admixture was applied in few layers with moistened spatula, till gaining of satisfying shape. After 12 hours areas of intervention was better shaped with help of turbine.

fig.7. click on to zoom fig.8. click on to zoom

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 (Zn2O) and rabbit skin glue was applied shortly afterwards in four layers. Every layer was left to solidificate for 15 minutes. The ground was applied on all surfaces. The new gesso was not applied on surfaces of batten and corner ornaments of very frame. Gesso was not necessary to apply on them due to fact that they would not be burnished and additional gesso would only urge change of delicate shape of ornament.
After 12 ours all surfaces of object were shaped with sandpaper. In order to prepare flat and smooth surface important for quality of water gilding. Sanded surfaces were 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 (fig.9., fig.10. & fig.11.).

fig.10. click on to zoom
fig.9. click on to zoom fig.11. click on to zoom
Bole mixed with 5% rabbit skin glue was applied in 6 layers and then gilding and silvering was performed by water gilding technique. After 12 our gilded and silvered surfaces were partially burnished.
Due to fact that this object will not be exposed to the circumstances of everyday use, final protection was carried out with prefabricated protection spray for luminous surfaces (4) in order to prevent process of patination of silver. Good feature of spray is anti static reaction so object will be protected from dust accumulation (fig.12., fig.13. & fig.14.).

Mounting

New elements for mounting of the crown and side elements were made of pinewood (Pinus nigra) and adhered oh the frame with heat reactive synthetic glue (5). Crown and side elements were placed on them and also adhered with heat reactive synthetic glue (5). Reason for using heat reactive synthetic glue was slightly curved profile of crown and side elements. Feature of the glue is to accumulate between curve shape areas and flat areas and to hold same characteristics trough the time.

fig.12. click on to zoom fig.13. click on to zoom fig.14. click on to zoom
List of Used Prefabricated Materials

1. Nitro thinner: HB Body , Grece
2. Aliphatic resin glue: Titebond wood glue , Franklin International, USA
3. Model plaster: Krone Hiliges Gipswerk, Germany
4. Protection spray for luminous surfaces: Kurt Vogelsand GmbH, Germany
5. Heat reactive synthetic glue: Crown GmbH, Germany

Applied Gold, Silver and Metal Leafs

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