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    Wednesday
    Feb222012

    Craquelure, what Montagnana feared.

    What causes craquelure?  When subsequent layers of varnish are applied too quickly, lower layers tend to dry at a slower rate due to the solvent effect of the layer that is applied on top, the reduced amount of uv rays, air.  The layers on top start to dry faster and as they harden they shrink causing wide gaps and the effect we call craquelure.  This effect can be faked by softening the varnish, some makers simply by applying a coat of alcohol, and then applying, with of without a brush, a quick drying varnish.  It could be an alcohol sandarac varnish applied over one or two coats of not completely dry oil varnish, or a water based solution of gum Arabic applied over a still soft alcohol or oil based varnish.  The thinner the soft coat is, the narrower and distant from one another the gaps will be.  If you desire to achieve wide craquelure as in the C bout photo, the varnish should be applied thick and still quite wet.  In this case one or more layers of egg white, could be applied with an airbrush.  Egg white will generate wide craquelure.

    I am sure Domenico Montagnana did his best to avoid this varnish abnormal behavior, see two Montagnana cellos with and without craquelure.  The craquelure on the Montagnana is particularly appealing because it varies in pattern.  I still have to see a beautiful convincing craquelure imitation, my colleague D.W. suggests we should make a varnish that will slowly gain such effect.  I think he is right.

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