Restoration of Oil Paintings

It depends on the working system. Aquazol 200, a poly(2-ethyl-2-oxazoline), is used at 10 to 25% in water; 10% ethanol improves penetration into apolar surfaces like oil paint. It is thermoplastic: it also allows consolidation with heat. Klucel G, hydroxypropylcellulose, dissolves in water below about 38 °C or in ethanol; in easel painting, it is used to consolidate matte or powdery paint, and it dries matte with little saturation. Lascaux Medium for Consolidation, an aqueous dispersion of an acrylic copolymer with high penetration, is indicated for loose and powdery paint layers on textile or wood supports. Its dry film dissolves in acetone.

It is a heat-calendered polyester non-woven fabric, with a smooth surface, resistant to solvents and tearing. In canvas painting, it is used in two ways. As an interlayer in relining, between the original canvas and the relining canvas: without weave and dimensionally stable, it serves to provide rigidity or to prevent the weave of the relining canvas from showing through. It has been used this way with BEVA 371, and Lascaux 375 P can be applied over such an interlayer. In perimeter strips, thin strips adhered to the edges of the reverse side join the painting to a heavier canvas, which provides the new tacking margins.

Both are thickened aqueous dispersions of acrylic copolymer; what changes is how the film works. Lascaux 303 HV is extremely elastic (elongation at break greater than 1000%) and its dry film is tacky: it is used as a contact adhesive in heat-seal relinings, and seals from about 50 °C. 498 HV is the standard type for relining and marouflaging: a hard elastic film, non-tacky, that seals from 68-76 °C and allows for wet or dry application, reactivating it with solvent. Once dry, 303 HV dissolves well in acetone, toluene, and xylene, and 498 HV in acetone, ethanol, toluene, and xylene.

The choice depends on the case; what changes is how each family works. Aqueous acrylic dispersions (Lascaux 303 HV, 498 HV and 498 20-X) are diluted in water and applied wet or by reactivating the dry film with heat or solvent. Heat-seal adhesives (Lascaux 375 P, 375 in dry mix, 375 film, and BEVA 371) are activated with heat. The 375 P, after the solvent has evaporated (about 24 h), seals at 62-65 °C on a hot table with light vacuum, iron, or heat gun. Lascaux 443-95 adhesive wax (microcrystalline wax and resin) is worked liquid at about 60 °C and seals at 68 °C, preferably with vacuum.

Isinglass is a protein fish glue; sturgeon isinglass can be obtained from the skin, cartilage, or swim bladder. With rabbit glue, the origin, preparation, and use change. CTS Sturgeon Isinglass is obtained from the skin; it swells in cold water, disperses when hot, and is indicated for joining and consolidating paint layers on canvas and panel. Divolo Firenze rabbit glue, from rabbit skins in granules, is soaked in cold water for 8-10 h and heated in a bain-marie without boiling (glue/water 1/7 to 1/10); it is indicated for gilding, canvas sizing, and restoration.

You work with a canvas stretching plier and a stapler. The pliers leverage against the stretcher and distribute the effort better than stretching with fingers alone. Staples should enter perpendicularly and completely, and be placed close together, about 1.3 cm apart. If the stretcher is wedged, it is advisable to let the canvas stabilize before applying more tension. To remount an original canvas whose tacking margin is insufficient, a perimeter strip of similar weight and material to the original is used; Lascaux 498 20-X is indicated for perimeter strips.