Comparing Varnish Resins for Oil on Metal Jewellery Pieces

Hello, 

This forum has been phenomenally helpful for me before and I’d really appreciate your expert advice (I’ve reached the end of my amateur internet sleuthing)!

I’ve been looking for the best varnish to complete some commissioned miniature paintings (I’ve asked about them before on here) – tiny oil paintings on solid 23ct gold, primed with Rublev Lead Alkyd Ground. They are produced for a client’s collection of high end jewellery to be worn as occasion pieces. My medium was progressively fatter linseed oil, Galkyd and Gamsol, sparingly used. They are convex and concave domes.

They will be encorporated into jewellery pieces, but sadly without a glass covering; this isn’t posssible with the frames and my client is aware that varnish can’t provide the same protection, but is the next best thing. The pieces will be sold with hefty care caveats such as avoiding perfumes and makeup touching the painting, not wearing the pieces under clothing, submerging, temp extremes…

As they will be worn the varnish needs to have a high glass transition temperature and be as durable as possible (hard, moisture resistant etc) – be stable on the domed surface and of course age well. Being skin safe isn’t critical as the painted surface won’t touch the skin and buyers will be encouraged not to touch the painting itself.

So I’ve been searching for this wonder product in the UK for a while now – my ideal varnish would seem to be Rublev’s Conservar Polymeric Varnish made with Paraloid B44 – it even has an affinity for metal bases – but they won’t ship it over!

My client doesn’t want a traditional varnish because of the yellowing. Nor a non-removable epoxy resin/urethane resin.

I’m limited by what I can buy in the UK (I don’t want to mix my own varnish from resin pellets) – after lots of testing and emailing technical departments I’ve narrowed it down to two varnishes, both made by Roberson’s; one is a gloss made with Laropal A81, the other Paraloid B67 with microcrystalline wax for satin finish, both in mineral spirits. They both look good in tests and don’t seem to react to the ground (I tried it directly on the cured ground as well as a cured paint test).

– Is there any property that I’ve missed that would make one or the other unsuitable/a better candidate for these pieces, given how they’re made please?

– I have to heat the Paraloid B67 with ‘very hot’ water in a bain-marie before brushing it on – could this hot/warm varnish cause a problem? My test seemed fine.

– Would a very thin layer of Renaissance Wax (microcrystalline) over the glossy A81 varnish to bring the shine down undermine all those useful properties from the varnish? It seems compatible in tests, but may be too soft?

Thank you so much for your time in reading all this, and any advice would be very much appreciated!

Kind regards,
Ellie