Conservation was undertaken to consolidate and stabilise the original painting. An old treatment was reversed, repairs to the cotton support and paint layers was undertaken, the painting was lined on to a new synthetic lining, stretched around a solid support and framed in a new frame behind low reflective UV protective acrylic
The treatment proceeded as follows:
- Painting removed from frame
- Back of the painting was lightly dusted with a soft mop brush and low-powered vacuum to remove debris and cobwebs.
- Painting was removed from its stretcher and laid flat on a table, face-up. A table large enough to accommodate the painting and its stretcher was covered with a layer of thick Melinex (polyester) and Tyvek (spun bonded polyoleofin). The painting was laid flat on the table, face-up. The tacks were removed with pincers and areas where the nylon net was stuck to the wood, were peeled away. The stretcher was eased out from under the painting and the painting left face-up on the Tyvek on the tabletop.
- Surface of the painting was dry-cleaned with a soft brush and vacuum to remove settled dust, avoiding areas of powdering / flaking paint.
- Nylon net that was adhered to the front surface of the tacking margins with PVA glue was removed. Adhesion of the net was found to be variable. In some areas it was easily removable by peeling from the canvas in sections at 180o angle or by sliding a Teflon coated spatula between the canvas and net. Other areas were removed using the solvent Acetone (propan-1-one/dimethyl ketone), applied with a fine sable brush to dissolve the glue. Extreme care was taken not to over-wet the surface as this spread of the adhesive into other areas of the original canvas and caused dark tide marks where the ‘liquid’ nature of the solvent appeared to disrupt the dark water-soluble degradation products within the canvas (thought to be the result of acid hydrolysis). (White Spirit is the only ‘liquid’ that can be used on the surface of the painting)
- Flaking and powdering paint layer was consolidated. Powdered / under bound paint was consolidated with Paraloid B72 (ethyl methacrylate copolymer), 2% in xylene, applied to the surface with a humbrol spray in 2 to 3 layers (check details) to achieve cohesion of the surface without wetting (as this would result in staining). The flaking paint of the central figure was re-adhered with an acrylic dispersion MfC (Lascaux 4176) 1:1 in reverse osmosis water. The area was first wet with White Spirit (composition variable - petroleum distillate) (using a brush). The adhesive was introduced beneath the paint flake with a small sable brush and the flake laid flat with finger pressure over release layer of Japanese tissue and Melinex. A small sandbag was left in place until the adhesive dried. The area was then uncovered to allow the remainder solvent to evaporate.
- The whole surface was cleaned with Chemsponge/smoke sponge (vulcanized rubber molecular trap, containing a minuscule percentage of mild soap i.e. <30grm per 500kg). in preparation for turning over. The painting was turned over on to a layer of Silicone (coated) Release Melinex.
- Removal of old lining. Nylon netting + PVA glue residues on the reverse were removed as for the tacking margins (see above). Small sections were cut away at a time. A second tinted later of nylon net was found on areas of previous tear repairs. This was left in place and removed at the repair stage (see below)
- Tears in the cotton support were re-aligned and mended with synthetic (Kasan-Shi) paper patches. During removal of the nylon net, the fragile nature of the canvas was revealed. Many areas were found to have very little cohesive strength. Patching material was therefore prepared to reinforce areas of severe degradation as well as to support tears and loss in the canvas.
Fine Japanese Kasan-shi (synthetic-shi) paper (100% polyester) was prepared with a spray application of Beva 371 (polyethylene vinyl acetate). (Beva371 gel was diluted 1:3 in white spirit and sprayed on to the paper in 15 fine coats. It is essential to test the tack and peel strength of the sprayed Beva for every case as this varies greatly with the delivery method. Ref:)
Tears were realigned and bridged with small patches of the prepared paper, heat-sealed to the surface reactivating the Beva371 adhesive using a heated spatula set to the melt temperature of the Beva371 (approx 68oc) over silicon release coated melinex. Larger patches were used where the support was severely degraded.
Preparation for new lining
- Original tacking margins were flattened to reduce creases. Tacking margins had become very creased as a result of the previous treatments. None of these creases relate to original turnover edges. (There is one crease in line with holes thought to be related to the original stretching of the canvas at the painting stage. These run along the very edge of the painting around the red borders on three of the sides.)
- Blotting paper damp with distilled water were placed beneath the creases isolated by a piece of Goretex (polytetrafluoro ethylene,polyester laminate) and the whole thing covered with melinex. After 5 minutes the blotters were removed and replaced with dry blotting paper and weighted from above with small glass weights until dry.
- Fragmented tacking margins reinforced with strips of same patching synthetic paper (as above). Many areas of the tacking margins were fragmentary as a result of their previous treatment and use / re-use to attach the painting to its previous stretcher.
Preparation of lining fabric.
Two 2 meter strips of Stabletex (100% polyester)(1m wide – wider is not available) were prepared with the same spray application of Beva371 as for the repair paper. Approximately 18 coats of Beva371 were applied to the Stabletex in same mix as for synthetic paper repairs (see above). The stabletex was stretched on to wooden strainers (looms) attached with double sided tape. One side was sprayed with multiple coats of dilute Beva371. The 2 stabletex pieces were then cut from the strainer and rolled between two sheets of Silicon release paper until needed.
- Lining fabric attached to the reverse of the painting. The Beva371 coated stabletex was heat sealed to the back of the painting, with the warp direction of the stabletex running from the top to bottom of the painting and overlapping the fragile central seam by 2cm. A hand held lining iron and large heated spatula were used, set to the melt temperature of the Beva371 (approx 68oc) to reactivate the Beva371 adhesive over silicon release coated melinex. The stabletex lining extended 10cm (check) beyond the original painting to provide new ‘tacking margins’ with which to attach toe painting to the new solid support (see below)
- The new stabletex ‘tacking margins’ were then prepared with strips of Beva371 film for use in attaching the painting to its new solid support. Strips of Beva371 film were heat-sealed to the reverse of the outer edge of the stabletex tacking margin (as above for lining), (approximately ?? cm beyond the edge of the painting) and the back of the strips was covered with strips of Kasan- shi synthetic paper. The paper was applied to prevent any glue from transferring to the front of the stabletex. These strips of Beva371 film would be used to attach the painting to the solid support. (See below)
- One strip of Beva371 film (3cm wide) was heat-sealed across the reverse of the top edge and tacking margin of the painting, on top of the stabletex lining.This was to aid support of the painting when on display in a vertical position once it was attached to the new support (effectively hanging it from the top edge of the stabletex lining)
- The painting was turned face – up and the front of the painting and the exposed stabletex tacking margins were vacuumed
- Tear mends were checked and secured, and the lining attachment refined using a small heated spatula through silicon release melinex
- Exposed sprayed Beva371 on the front surface of the stabletex tacking margins was removed. White spirit was applied on small cotton wool swabs to dissolve the glue. It was necessary to remove the exposed Beva371 because it remains tacky and will pick up dirt easily.
Preparation of padded mounting board / support
All synthetic materials were chosen so as not to introduce the potential for increased acidity. It was not possible to undertake any deacidification procedures due to the extreme fragility of the painting. The choice of inert materials also reduced the structure’s response to environmental changes, thereby having minimal impact on the painting and reducing the risk of sagging of the support fabric.
A rigid, slightly padded support board was constructed on which to mount the relined painting. Sheets of Hexlite board (aluminium honeycomb with fibre glass and epoxy resin outer skins) were joined using 'top hat method', (the join running vertically down centre), to form an overall board approximately-??cm larger than the painting all round. This board was then prepared with layers of padding and fabric covering, leaving a carefully positioned recessed channel (c 4cm wide) for the central seam of the painting to sit in. The first padding layer was medium weight Vilene (type), attached in two strips glued to the top surface of the Hexlite with PVA (Vinamul 3252), leaving the central recess, where a coat of PVA adhesive was painted. The second padding layer of thin cotton domette was stretched around the front and heat set glued to the reverse; it was also glued down into the central channel on the front. A strip of Beva371 film (width) was heat-sealed down the central channel. A piece of Lascaux P110 100% polyester linen look material was stretched around the panel (check direction of warp), same as the domette and the centre heat-sealed down on to the Beva371 film. A backing fabric of cotton lawn was sewn (stitch type) to the edges of the LascauxP110 (on the reverse)
-The painting was attached to the padded support board with slight tension. The stabletex tacking margins were wrapped around the edge of the board and heat-sealed to the reverse of the lascauxP110 by reactivating the Beva371 film strips at the edges.
- Strips of the synthetic paper patching coated with sprayed Beva371 (as above) were attached around the edges of the board covering the Stabletex. The strips extended 2mm on to front surface of the board and 5mm behind, to protect the fragile stabletex edges wrapped around the board edges during handling and from impact damage before the painting was fitted in to its permanent frame.
- A single line of running stitch with Skala polyester thread was used around the very edge of painting, through the stabletex lining in to the Lascaux P110 fabric to further secure the painting in position.
- The Beva371 film strip beneath the top tacking margin of the painting was heat-sealed from the front (as above) through silicon coated melinex. Great care was taken not to over-heat the vulnerable surface of the painting.
- Polyester tabs were attached to the reverse of the support. This was to aid future removal of the support board from the frame and was also used to temporarily secure the painting and support in a vertical position on a painting easel during MOLAB investigations.
In-painting of the losses to the image
-Areas of loss to the original canvas, revealing the white patching paper beneath were in-painted with raw pigments (primarily cobalt blue, ivory & lamp black, titanium white, yellow/brown earths, indian yellow and crimson red) mixed in a medium of 20% Paraloid B72 in Methoxy propan-2-ol (also used as the diluent). A very small amount of the medium was used to reduce the risk of a shiny finish to the in-painted area. The exposed paper patches were coated with beva 371 and in places this was activated with the solvent diluent rather than adding additional medium, to avoid increasing the gloss of the restorations.