Acid Burn on a Watercolour

When having your art framed it is important to consider the use of conservation mount board. Mount board comes into direct contact with the artwork and should therefore be chosen to ensure that no damage is caused to the artwork, this is particularly important if the art has value or is expected to gain in value in the future.

The effect of using non-conservation mount board includes ‘acid burn’ and discoloration.  Acid burn is caused by the oxidation of lignin’s in the paper the mount board is made from.  The oxidation process releases acids and other reactive substances and it is these that can cause damage to the artwork.

A classic symptom of acid burn are the yellowish-brown stains that appear around the edges of the artwork where the mount come comes into contact with the paper. If a non-conservation backing is used, and not protected from the artwork by a barrier board or under mount, the acid burn can spread over the entire artwork.  Acid burn is common in older artworks framed before conservation materials became more widely available.

Not only will acid burn cause your art to become discoloured, but will also make the paper brittle and weak, leaving it open to further damage, such as easy tearing and further deterioration.

I have a water colour sketch in the workshop and I thought I’d share a couple of photographs showing the kind of damage that using non-conservation boards and framing techniques can do. There is a post here which also discusses the problem.

Acid Burn 1The photo shows the bottom left corner of the painting; the brown stain can clearly be seen.  This is ‘acid burn’. I am reframing this sketch with conservation board to ensure its long term protection. It is possible to have browning removed by specialist paper coservators but it can be an expensive exercise, much better to avoid it in the first place.

water3Another region of the same picture also shows signs of browning, but another problem – cockling – is also present. Cockling is caused by using tape incorrectly, in this case a strip of selotape was used to hold the picture in the mount.  The picture expands in changes of humidity and cockling is the result.  This will be the subject of a future post.

How to spot the early signs and avoid acid burn

Fortunately it is possible to check to see if there is a risk of future damage to your art from inappropriate mount materials. A simple check of your framed items will soon reveal the tell tale signs of browning in the bevel (cut inside edges) of the mount boards.  If you have items that you value then please consider having them reframed using conservation grade mount board.

bad-framing.jpgThis is an image from an earlier post showing the browning that occurs in non conservation grade mounts. Unfortunatley nothing was done to resolve this problem until too late as can bee see in the clear browning of the edges of the map.


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