[Michael]

Paul Foxton has a video in which he mixes the neutrals using raw umber and burnt umber to make a neutral dark. Then he adds white as needed, adjusting as he goes.

[Michael]

Shellsol A is naphtha and has about the same solvent strength as turpentine. It evaporates quickly like mineral spirits.

Odorless mineral spirits has less solvent strength than regular mineral spirits and regular mineral spirits has less solvent power than turpentine. Any of them has the potential to remove the cured paint.
When removing varnish from a painting only small amounts of any solvent should be used. If you see paint appearing on the cotton ball you should stop before you damage the paint layer.

I’m not familiar at all with Paraloid B72 and my experience with removing varnish from a painting is with removing Gamvar using Gamsol. Gamvar is a Regalrez based varnish and Gamsol is simply odorless mineral spirits.

What I would do is to go back to the conservator at Kremer Pigments and ask them about the potential for damaging your painting with the Shellsol A. So far, I haven’t found much useful information on the Senellier brushable gloss varnish except for the warning that it is difficult to remove is is dispersed in turpentine.

From your photos, it looks like the varnish was applied in a very thick layer. It should only be applied in very thin layers. I’ve seen YouTube videos that teach pouring a puddle of varnish on the painting and then spreading it around with a brush. Not knowing any better, I did that when I first varnished some paintings and the result was terrible! That’s how I got my experience with removing varnish! The video on this site gives authoritative instructions.

At this point, I think that going back to the conservator at Kremer is your best bet for how to proceed. Then proceed very cautiously.

I just bought the course on cleaning paintings and it gave me a link to start the course. It doesn’t give information on varnish removal though.

I hope you get your paintings repaired!

[Michael]

Looking at Sennelier products, I see that they also have an acrylic spray varnish. Which varnish did you use?

[Michael]

I looked on the Sennelier website (as you probably did) and couldn’t get much help. They only point out that their varnish is “difficult to reverse”.

Winsor-Newton has instructions for removal of dammar varnish and recommend using distilled turpentine. It is also the solvent used in the Sennelier varnish. Distilled turpentine is a stronger solvent than mineral spirits so it is your best bet. I can’t find what the varnish resin in Sennelier is yet. I’ll keep searching.

Here’s the Winsor Newton article: How to remove varnish from an oil painting | Winsor & Newton (winsornewton.com)

Proceed carefully. If you notice that paint is beginning to be lifted, that means the varnish is gone from that area.