Restoring the Walker Art Gallery's Altarpiece
In January 1962 the conservator Jack Coburn Witherop examined the Walker's two wings by the Master of the Aachen altarpiece.
How was the painting produced?
Under examination the paint was found to have complex layers of alternating tempera and oil media. It
is thought that the gold haloes and the embroidery on the garments would have been applied last. The
ornament on the armour was applied using impasto and other areas of similar texture were applied in a
thick tempera medium. This had sometimes been applied over oil glazes and sometimes underneath them.
Which areas needed restoring?
The varnish layer was discoloured and there were poorly colour-matched retouchings in damaged areas.
Small areas of the ground layer were found to be flaking around the edges where the panel's original
frame was once positioned. Damage was discovered on the torso of Christ where the joints of the panels
were weak. Small areas of blistering were found on the head and shoulders of St Joseph, which are
thought to have been caused by an altar candle being placed too close to the painting.
How were the damaged areas treated?
Loose fragments of ground were re-secured to the support with an adhesive and the level restored with
a small amount of filling material. The discoloured varnish was removed with a solvent in two ways,
with a cotton wool swab for large areas and a sable brush for smaller areas. The discoloured
re-painting was then removed with a scalpel. Finally the painting was re-varnished with a layer of
Cleaning the Altarpiece's wing panels
An exciting discovery was made during treatment of the work in 1963. When the conservator J C
Witherop examined the reverse of the altarpiece wings he saw signs of a raised design in gesso underneath a thick layer of dark brown paint. This paint was covered in a variety of exhibition
labels dating back to 1857. Cleaning tests revealed that both reverse surfaces had originally been
painted with images of the donors of the altarpiece and their coat of arms.
Labels on the reverse of the altarpiece
To reveal his discovery he used a wax paste prepared by
'emulsifying bleached beeswax with ammonia'.
This was applied to the surface in small areas at a time and left on for some minutes to help soften
the paint layer. Once the brown paint layer was swollen, it could then be carefully peeled away using
How were the painted images covered?
The images had been covered over by a thick layer of dark brown paint. This was first thought to be a
protective layer, applied to prevent moisture damage to the panel. However, this dark brown paint
may have been deliberately used to hide the paintings.
Notes on JC Witherop and the conservation work on the wings of the Altarpiece