Deacidification vs bleaching. Watercolour restoration

  • Owner: Private collection.
  • Artefact: Watercolour drawing by Rafael Estrany.
  • Damages: Foxing stains.
  • Restoration treatment: Wet cleaning and deacidification with calcium hydroxide.

(castellano / català)

Before we decide to bleach in order to remove foxing stains, we sholud assess whether the benefits of a deacidification give an acceptable result or not. Deacidification, unlike bleach, is good for the preservation of the document because it provides an alkaline buffer. Bleaching treatments, either with sodium hypochlorite (bleach), hydrogen peroxide or other products, carry RedOx reactions which weaken cellulose fibers and may involve a revival of the spots we intended to remove. The goal of deacidification is not to remove stains, but it may be a desired consequence of it, at a certain degree.

fugitivity test

test on inks fugitivity previous to washing.

Aquarel·la Estrany

Watercolour during wet cleaning.


Aquarel·la Estrany

Left: Detail of foxing stains before treatment. Right: after washing and deacidification.

Watercolour restoration Estrany

Watercolour after (top half) and after the restoration (bottom half). Digital photomerge with the two original images.


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Why deacidify if it is hardly visible?Deacidification / Bleaching/ Foxing