Fake craquelure on paintings

Sylvia Krauss <sylvkra [at] web__de> writes

>While examining an Italian 15th century panel painting in our
>collection, we have observed a very fine, accurately executed fake
>craquelure pattern which is only observable under magnification. The
>fake craquelure is located in an area of green drapery in the
>background which has been over-cleaned in the past. ...
>...
>Has anyone come across a similar false craquelure pattern or is able
>to suggest a plausible technique to produce one. We would be most
>grateful for any suggestions or comments.

Cracking of a varnish layer to produce the illusion of craquelure is
fairly straightforward and there are 2-part commercial products that
do this. It should be fairly easy to distinguish from genuine
craquelure under magnification.

A layer of the varnish is applied and once it is touch dry a
cracking medium is brushed over it. The varnish layer should be
pulled apart by the quick drying, contracting cracking medium. There
is a window of time in which the cracking medium can be applied
before the varnish is too dry. Within this window you have some
control over the size of the cracking. Applied early it will produce
very large cracks, applied later it will produce very fine cracks.

I believe different varnish solutions will produce different cracks,
i.e. it is the varnish used and not the cracking medium which
determines the crack pattern. Once the cracked varnish has dried, a
dark patina paste is rubbed into the cracks to make them visible.

The process is completed by applying a second layer of the varnish
over the top. The varnish may be tinted or aged. I believe an
example of a cracking medium is sugar solution (which would be
soluble in warm water). I hope this helps and look forward to seeing
other contributions on this.

Jevon Thistlewood
Paintings Conservator
Ashmolean Museum of Art and Archaeology, University of Oxford


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                  Conservation DistList Instance 24:20
                Distributed: Wednesday, October 13, 2010
                       Message Id: cdl-24-20-006
                                  ***