A lithograph by Camille Pissarro, printed on Dutch handmade laid paper.
A bleach (possibly a commercial household bleach) has been used in the past to lighten the effect of foxing spots.
The yellowing around the edges of the print is due to prolonged contact with an acidic window mount. A thin, more strongly discoloured line can be seen around the edge of the image area – this is mat burn, caused by volatile acids given off from the cut edge of the window mount.
The print has also been on display for a very long time, causing the paper to darken.
Can the damage be repaired?
This print was treated by a conservator to order to reduce acids in the paper and to improve its appearance. (See the “after treatment” image below).
The print was washed to reduce discolouration and lightened overall using light bleaching and an alkaline bath.
In this case the appearance of the print has been improved a great deal. It is not always possible to reduce staining to this extent.
What could have been used instead?
It is generally better to leave discolouration such as foxing spots alone, as too many things can go wrong during treatment – especially if inappropriate treatment solutions are used.
A conservator may use water or solvent washes or a bleaching method to lighten stains; however this will be done in a very controlled manner, using mild bleach solutions that have been tested to ensure they do not leave harmful residues behind. As all bleach solutions, however mild, are somewhat damaging to paper fibres, it is not a treatment to be undertaken lightly.
Chlorine and household bleaches should never be used on cultural heritage materials – they are too strong and leave damaging residues in the paper.