Mediums and Varnishes used by Artists in the early 19th century

Academic art training in the early 1800’s did not endow the artist a sound technical knowledge. Artists seriously attempted to improve their craftsmanship by studying the work of the Old Masters to discover their supposed “secrets”. Led by surmise, they resorted to technical experimentation that often led to poor and unstable results. Many of their paintings have thus deteriorated within a comparatively short period. Before the advent of paint in lead tubes in the 1870s, artists purchased their prepared paints in small bladders from the colourman. They also experimented with the new and wide variety of pigments that were available on the market as a result of the discovery of coal-tar derivatives and new dyes. The most problematic “pigment”was Asphaltum (Bitumen), which was extensively used. Used it in great quantities in this period, it produced semi-transparent, reddish-brown rich glazes which were perfect for emulating the “look” of an Old Master painting. If normal paint was applied over asphaltum, it often cracked as the latter seldom dries and these layers were drying at different rates. Asphaltum also softens with heat and causes contraction cracks and an “alligatoring” pattern (like reptile skin), which are both commonly seen.

Artists of the early 1800s wanted to emulate the transparencies and textures that they admired in the work of Old Masters such as Titian and Rembrandt. To achieve this, they experimented with numerous resins, balsams and wax combinations to make paint media. Mastic varnish, made by dissolving mastic resin in turpentine,was often added to the paint; Elemi resin or Venice turpentine were also sometimes added. Varnish made with mastic resin soon yellows with age, embrittles and blooms readily in a moist atmosphere. When used as a painting medium these defects transfer themselves to the paint and ended up distorting colour values.

Megilp was another favourite but disastrous medium. It was made by dissolving mastic resin in turpentine and adding Linseed oil. It had a gelatinous, buttery consistency, which had excellent working qualities; giving body to the paint. It had a tendency to remain slightly tacky, but gave the paint a luscious, glossy finish. When used in large quantities it caused cracking, embrittlement and rapid yellowing with age.

Copal varnish, made by dissolving ground copal resin in hot drying oil,was also very popular as a medium. Copal is a fossil resin with a hard, thick and dark character, which increases with age. It is liable to crack, particularly if mixed with driers, oils and other varnishes. A combination of beeswax and Copal was also very popular because artists thought that the hard nature of Copal and the plasticity of wax would counter balance each other.

Two balsams were also used: Copaiba and Venice turpentine. Copaiba, an oleo-resin, was used to give the paintings a textured effect. It also yellowed with age.Venice turpentine in turn gave a glossy effect. If used sparingly the latter could be nonyellowing, but it was characteristic to use all of these painting media in abundance. As well as being used as a protective “varnish”,wax was also commonly used as a painting medium. It was either used by dissolving it in white spirit and Venice turpentine, or combined with Copal varnish. Often a thin layer was applied as a base to paint on. This gave the paint body a rich, textured surface.

Siccatives were often added to accelerate the drying of the slower-drying paint additives. For this Sugar of Lead and probably Red Lead were used. When incorrect proportions of these were added to the paint, it could result in cracking of the paint layer.

The aim of the final varnish layer in a painting was to protect the paint layer and bring out the full tonal range of the colours. If desired, a tint could be added to the varnish. A popular varnish was a layer of glair followed by a layer of Venice turpentine. Glair is the albumen of an egg, which is of course moisture sensitive. It gave a painting an even, glossy surface and although it was intended as a temporary varnish it could never be completely removed. In many portraits the glair has caused decomposition of the underlying layer, resulting in a bluish tone. It also caused serious cracking in the paint layer. A multiple varnish layer was often composed of glair, drying oil and wax. These layers were sometimes applied without adequate drying time between them and wrinkling and cracking often occurred as a result.

Another favourite final varnish layer was a hard varnish resin with two layers of a soft resin on top of it. Copal and Dammar resins were generally used. The artist was concerned with preventing discolouration of the varnish as it aged, as well as the dangers of cleaning and restoration. The intention of this technique was for the Copal varnish, a hard resin, which is insoluble in most solvents, to protect the paint layer without discolouring, owing to the layer above it. The Dammar varnish, a soft resin, could then be removed whenever it became too discoloured.

Artists in this period often tinted their varnishes with coloured resins. Commonly Gamboge was used but Shellac, Dragon’s Blood and Gum Accroides could also have been used. This gave the painting a “golden glow”that the artist so admired in the work of the Old Masters. This was in reality merely discoloured varnish.

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