Removing an acidic backing to recover the stability and original appearance of an early nineteenth-century watercolour.
Overview
This watercolour by Nicolas Pocock (1813) had been fully adhered to an acidic secondary board, a common framing practice in the past but one that had become the principal cause of its deterioration. Over time, acidic degradation products had migrated into the original paper, causing widespread staining, weakening the support and altering the artwork’s original colour balance.
Conservation Strategy
The priority was to remove the source of deterioration rather than simply treating its visible effects.
As the original watercolour was particularly sensitive, the backing could not be detached using conventional methods without risking damage to the artwork. The treatment therefore focused on separating the two supports safely before stabilising the paper and recovering as much of its original appearance as possible.
Treatment
After careful surface cleaning, the secondary board was gradually reduced by hand until only a thin layer remained. Controlled moisture, applied through cellulose-based conservation gels, allowed the final layers of backing to be removed with precision while protecting the painted surface.
Once separated from the acidic support, the watercolour underwent a series of aqueous treatments to remove degradation products, improve the chemical stability of the paper and recover much of its original tonal range. Controlled flattening restored the planarity of the sheet before the artwork was rehoused in a bespoke museum-standard mount with UV-filtering glazing.
Outcome
Removing the acidic backing halted the principal cause of deterioration and significantly improved both the stability and appearance of the artwork.
The treatment partially recovered the watercolour’s original tonal balance, strengthened the paper support and provided a museum-standard framing system that will help protect the artwork for future generations.
