Varnish ?

[H R Fisher]

  Is it ok to use spirit varnish  as a sealer under oil varnish, or using spirit varnish over oil varnish?

  Thank Henry

[FiddleDoug]

Shellac often gets used in ground formulations. so under may be OK. Retouching varnish is almost always a spirit varnish, so over should work. I wouldn't totally overvarnish an oil varnished violin with spirit varnish.

[H R Fisher]

Thanks Doug. I  read an article recently that stated that putting oil over spirit varnish is problematic. I was a bit paranoid and needed some confirmation. I have been using spirit as a sealer for a number of years.

[HoGo]

The rule is fat over lean which in language of oil varnishes means more elastic over less elastic.

Not all spirit varnishes are less elastic than oil varnishes (as is popular belief) so answer is "depends".

If you are looking for ground or sealer that won't make layer abovelevel of bare wood then anything that next layer will adhere to well is OK - dewaxed shellac is very good for that, though not really "cremonese". If you apply full layer(s) of softer (possibly oil) varnish and over that layer(s) of less elastic varnish you may experience crazing, cracking or even alligatoring of varnish. Also covering slowly curing varnish with faster curing may cause problems with the lower layer trapped shrinking for a long time after upper layer is cured causing wrinkling if teh outer layer is elastic enough or cracking (again the layers don't have to be different types of varnish just different drying properties)

[Tim M]

Just emphasizing what HoGo mentioned, above: a major component of many spirit varnishes is shellac. If the shellac is de-waxed, oil varnish will stick to it when dry. If it is not de-waxed, oil varnish will not stick well.