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Question asked 2020-02-11 21:31:19 ...
Most recent comment 2020-02-13 14:02:43
Industrial and Non-Traditional Products
I do multi-media work on Ampersand's panels and use multiple coats of Golden's archival spray varnish as a protective coating. Recently, out of curiosity, I lightly sanded Golden's gloss varnish and top coated it with 2 coats of nitrocellulose lacquer. To my surprize, nothing terrible happened, at least visually at this current moment in time.
I understand that lacquers are a no-no do to their propensity to crack and amber with time. But, could they be used on top of an archival varnish solely for the purpose of aesthetic reasons? I have always been told that brittle products can't be used on softer ones, but I have been asking myself: so what if the nitrocellulose lacquer cracks and slightly ambers in 100 years? (A person I spoke to from a lacquer manufacturer told me that today's Nitrocellulose lacquers are not the same as the ones first developed), that they take a much longer time to crack and significantly yellow). As long as Golden's archival varnish is the actual protective layer (used as the permanent layer), couldn't two thin coats of spray lacquer be removed by physically sanding it off? And since lacquers re-wet themselves, couldn't the picture just be recoated with new lacquer, or a new invention(hopefully after a 100 years) that isn't so plastic looking?
Grateful for any thoughts,
Answers and Comments
There are a couple of issues that you haven’t considered. First,
depending on the solvents in the CNL, it most likely bit into or even dissolved
itself into the lower MSA varnish making the scenario you mention impossible. Generally,
the solvents used for CN are hotter (read more aromatic or more polar) than
those used as typical diluents for fine are varnishes. It is true that current
CNL are different and perform better than earlier formulations, they are still
a very poor coating for organic paint layers. They may, and I emphasize, may, have
a place in coating metals with high surface energy and that require a
completely covering coating to prevent corrosion (eg silver objects). Even this
is debatable, and I foresee the abandonment the use of CNL for silver coating
in the relatively near future.
It is always best to apply more flexible coatings over less
flexible coatings/layers for very simple and understandable concepts. Why
deviate and for what gain. If there is an aesthetic goal, I could understand
but what does a surface coating of NCL gain you; a super smooth/super high gloss
surface coating? I would suggest that this could be achieved using less drastic
Finally, you do not mention if you intend on using this
rather dubious material, in terms of fine art application, on a work executed
on a rigid or flexible substrate. If the former you can probably get away with
it in the short term, if the latter, this is likely a poor decision.
Pretty much all picture varnishes are thermoplastic resins and would become soft when touched by warm hands and leave finger prints. Harder, thermoset resins, which are resistant to impact damage and finger prints etc, are generally very difficult, if not impossible to remove in a conservation treatment. Sanding down a coating without damaging the layers underneath would take tremendous skill and while you might be able to do that to an extend that meets your standards, it is unlikely that you'd be able to differentiate between the MSA Varnish layer and the lacquer once the surface is roughened up. If the lacquer layer is thinned down a little by sanding you might be able to remove the rest by using a solvent that removes the MSA Varnish. MSA Varnish is removable in aromatic mineral spirits or turpentine and the solvent might 'undercut' the lacquer, so that you might be able to remove both layers in one go. But this is not something we have tested and not necessarily a recommendation. Maybe you could consider putting your painting in a frame so that there would be no need to touching the artwork itself when handling. That would allow you to choose a removable picture varnish that produces a finish you like.
I will let those at Golden comment about their products but
no, as a conservator, if it requires sanding, it is not archival. That is even
avoiding the nebulous definition of archival.
We, that is Golden, recommend 6 spray coats of the Archival Varnish, which is comparable to 2 brush coats of MSA Varnish, and should provide the most UV protection. As I said earlier you might be able to undercut the lacquer and remove the Archival Varnish together with the lacquer, especially if the surface was roughened up a little and the solvent has better chances to penetrate down to the MSA coat. But this would be a very unorthodox approach. A simpler solution would be a frame, even without glass, that would allow you to pick up and handle your paintings without touching the surface. There are varnishes with resins of smaller polymer sizes which have less of a 'plastic' look, for instance Regalrez 1094 sold by Gamblin and Natural Pigments. Should the Regalrez require removal at some point you could do that with OMS without removing the MSA/Archival Varnish.
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