Saturday, June 7, 2014

The care of antique works on paper

Porcupine, 1951, woodcut by Leonard Baskin
All works on paper have special needs; some problems, such as the damage caused by sunlight, have been touched on above, but this needs emphasis, and other risks need to be mentioned. Whether used for drawings, watercolours, prints or books, the healthy survival of paper, or otherwise, depends upon its quality. Until the early nineteenth century paper was made from linen rags, and the cellulose content in linen meant that added chemicals were unnecessary: this type of paper is the most resilient.
Paper made from wood pulp, as much was from the 1840s onwards, included lignin, an acidic light-sensitive substance which eventually turns the paper brown and brittle, while certain methods of sizing paper, and bleaching it, have also caused susceptibility to damage.

Hanging and storage. Because of their delicate nature, works on paper need to be protected from bright light of any kind and from extremes of humidity and temperature: 50-60% relative humidity and 20-220C is ideal. Protection from ultraviolet light with special window film can be a worthwhile investment.Valuable works should never be photocopied. Pollution in the air, and condensation inside a picture frame (causing foxing) are further risks.
Hilaire-Germain-Edgar Degas (1834-1917), Paris Dancer, charcoal on paper
Always site these works on walls where direct sunlight does not fall. In addition, sun blinds or curtains drawn across windows are advisable, while individual curtains over particularly valuable works should be considered; in some cases ultraviolet-filtering picture glass or UVA Perspex may be used instead of conventional glass when framing. However, Perspex should not be used with friable materials such as pastels
or chalks, and it is important to bear in mind that it attracts dust and is easily scratched.

The Old Welsh Bridge. Watercolour by Paul Sandby 1715-1809. Shrewsbury Museums Service
Framing. Acid-free materials for mounting, whether for display or storage, are vital: lignin in paper, old backboards and mounts can leach through to works of art and damage them irretrievably, and should always be changed if found. Backboards of wood or non-acid-free cardboard should be replaced even if damage from them is not yet evident. Self-adhesive tape such as masking tape or Sellotape should never be allowed to touch the work itself, even the back, nor should the picture be in contact with the glass: use a mount or a
fillet to separate them. Sticking a picture down on a backing board, and dry-mounting are to be avoided. Instead, it should be attached to its support with an acid-free paper hinge using PVA adhesive or bookbinder’s starch paste.

When choosing a picture framer, always make sure that conservation or museum quality products and methods are used. BADA members will be able to recommend appropriate craftsmen.In addition to the general principles explained above, the attributes of drawings, watercolours and prints deserve special consideration, particularly with regard to conservation measures.

Totentanz (Dance of Death), illustration by Michael Wolgemut from Liber Chronicarum, also known as the Nuremberg Chronicle, 1493, by Hartmann Schedel
Drawings in crayon, pastel, chalk and charcoal should be stabilised to prevent accidental damage to the medium that might smudge or crumble if touched. This is emphatically a job for an expert picture conservator.

William Mulready, 19th century drawing, black an red chalk on paper
Fading of pigments is a particular problem with watercolours that are not displayed with adequate safeguards or stored correctly. The brown spots known as foxing, caused by damp conditions, can usually be ameliorated by a professional conservator, but there is no remedy for fading. The most vulnerable pigments are indigo, vandyke brown and carmine, but damage to any of the colours can change the whole nature of a picture.

Prints and maps should be treated in the same way as watercolours, and any signs of damp or damage should be referred to a paper conservator immediately. It is recommended that unframed maps and prints should be stored flat in acid-free boxes or archival wallets, such as those manufactured by Secol.

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