CONSERVATION OF WATERCOLOUR PAINTINGS IN THE BAILEY BEQUEST

Previous Condition: These watercolours were pasted onto cardboard supports of varying origin. All of these supports were of a poor quality in that they were of a commercial nature and acidic in content. In some cases, these boards also had self-adhesive tape which were again acidic and even had an unstable gummy component which could have caused damage to the actual watercolours themselves.

Discoloured spots, which we call “foxing” was evident in certain areas of these watercolours. Foxing usually appears as brown spots – so named because they are said to resemble the print of a fox's paw. If not treated, foxing marks will eventually destroy the paper. Foxing is caused by a number of possible factors ranging from excessive humidity to inherent flaws in the paper-making process. Poor quality paper as it gets older. It is therefore very important to store and exhibit works on paper in a controlled environment.

Some of the watercolour pigments used by the artist were “fugitive”, by which we mean that they are light sensitive and prone to fading with time. Fugitive watercolour pigments were much used in the second half of the 19th century following the invention of new colours, particularly those based on chemical dyes, many of which have not stood the test of time. Fading and discolouration of the paper are accelerated by exposure of the watercolour to excessive light and excessive relative humidity. Excessive light levels, which contain ultraviolet light, can even cause the fibres of the paper itself to disintegrate in time. Light damage is cumulative and irreversible. Lighting and humidity levels are therefore carefully controlled and monitored in the art museum environment.

Recent treatment: These delicate watercolours were removed from the boards onto which they had been pasted. They were then cleaned with Chlorine dioxide which acts as a mild bleach. The Chlorine dioxide was then rendered inactive by immersing each work in a solution of Sodium Thiosulphate. To remove any harmful acidic content in the paper, each watercolour was then deacidified with Calcium carbonate. They were finally lined with a special acid-free Japanese tissue paper. These are standard procedures used by paper conservators for cleaning watercolours and stabilising the paper supports. It is always important that paper’s pH level is kept as neutral as possible. It is an aim of all conservation interventions and processes that they be easily reversible.