Ivory miniatures

One of the most common problems with portrait miniatures is the
warping of the ivory support. Over the years I have come to the
conclusion that the primary cause for this effect is the paper card
which is usually glued to the reverse of the portrait. The ivory
sheet shrinks with age. The proportion of shrinkage is greater
across the grain of the ivory which is usually presented in a
vertical plain with the sitter of the portrait. While the ivory
shrinks the paper or card does not and thus causes a warping forward
in the direction of the painted side of the ivory. Some continental
artists painted with the grain in a horizontal plain and thus the
warp is in a horizontal plain with the sitter. Solution: One can
construct a balsa wood block the same shape as the warped ivory.
Cover the wood with a sheet of Mylar and place the portrait face
down on the block of wood. This will allow a support for the ivory
while one shaves and scrapes the paper and glue away from the
reverse. This will only alleviate the further effect of warping and
it may allow the ivory to flatten a bit on its own.

Now, here is where the controversy begins. I was given a formula
some years ago from James Murrell of the Victoria and Albert Museum.
It consisted of 5% almond oil, 10% acetic acid and 85% industrial
methylated spirits. This was to be applied with a swab on the
reverse of the ivory and the edges of the ivory set atop narrow
blocks in a humidity chamber with the bulge weighted to encourage
flattening. This would require constant monitoring. I have found a
more practical and safer method. Once the card is removed, put on
surgical gloves and hold the miniature face forward and with a deep
breath, exhale on the painted surface, then place the painting face
down on a surface and allow the ivory to flatten on its own for a
few minutes. Once the ivory is flat apply the solution and place one
edge of the ivory on a 1/8 inch thick strip of wood. Then place a 50
to 100 gram weight on the rear of the ivory just inside of the wood
strip. The weight will very depending on the thickness of the ivory.
You will want to use a weight to just hold tension, but not to bend
the ivory forward as it might crack. Allow this to sit overnight.
This process may need repeating several time until the ivory is
stable.

Painting conservator
Wiebold Conservation Lab.
413 Terrace Place
Terrace Park, Ohio 45174
USA
513-831-2541
Fax: 513-831-2815


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                  Conservation DistList Instance 16:77
                  Distributed: Wednesday, June 4, 2003
                       Message Id: cdl-16-77-002
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