MITRA Forum Question Details

Hello there,

I'm sorry for your troubles, I would hate seeing the same things occur.

In these complex situations it's hard to pinpoint exactly one single element that went wrong.

Here are my best clues to explore nonetheless, for this current issue and onward:

It's not clear whether it's both layers that peeled or only the second one. Most comments below assuming it's just the second one:

The first varnish sealed the painting and gave a non absorbant surface ("toothless"). The second varnish and its solvents couldn't solubilise it enough to fuse, nor had surface asperities to mechanically hold. 

So the Senellier one gently was glued to the smooth paraloid like even gouache can stick to glass, and dried without real adherence. Now it peels as if it was a vinylic emulsion. (I'm surprised by how soft it is for a varnish) Maybe this varnish doens't have much "stickiness" for itself. Hard to judge from this alone.

My hypothesis there is the first varnish did too good a job against the second varnish. There might not be anything wrong with either of them nor your painting.

First thing is, using materials from multiple suppliers makes it harder for them to safely advise you or support you. If all your products from colours to varnishes came from the same supplier, and you called their support line, then they'd ought to give you some of their time to investigate proper. They know their own products, but they can never know what their competitors do or use. So you'd put either company in a difficult position asking for advice about a combination of products.

Drying time are good. Was there a lot of humidity in the air at the second layer? Did you wipe the surface with alcohol before applying the second layer? Maybe there was some thin mist or dusts that prevented the good adhesion of the second layer.

​Playing with solvents available, WS to dissolve the paraloid and turpentine to dissolve the Sennelier gloss varnish, you can probably retry something with just these two, by applying a mix of the two between the two. However I wouldn't advise this if you can avoid it.

I've lost my technical file that compares the solvent affinities of the different grades of paraloid, but assuming this one is more soluble in aliphatic solvents and less in partially aromatic ones like turpentine, it's possible turpentine will solubilise only the Sennelier varnish, allowing its removal without damaging your paraloid varnish below. Test in hidden corners first though, don't take my word for it. Otherwise, you'd probably be best removing everything carefully with white spirit before revarnishing. Tough job unfortunately.

For the future, as thorough as it is, the use of two layers varnishes might not be absolutely needed for your purpose? You might want to reconsider this approach with the idea that for art restorers, the simpler might be better.

Another tip in complex systems might be to have smaller test swatches for the next paintings. Like a small separate canvas corner or board you keep on the side and paint a little (randomly) with the same colours or palette leftovers as you paint the main work. Same products at the same time, same drying time. (safe surface too ideally)

That way you have a side "same painting" to test your varnishes and systems on, before going for the real deal. Varnishing being often the critical moment with yours here being an unfortunate example, having a test swatch of your paintings onward might save you some dread and white hair.

Now if it's both layers that peeled off together, it means it's the paraloid one that didn't have enough tooth and stick.

One possible reason also hinted at, it's as oils dry, they release some smaller particles and dust. If you didn't wipe it out before varnishing, you've possibly essentially varnished over a thin layer of dusts that didn't bind to anything. It would depend on the colours and the mediums used heavily. However if it's the same everywhere no matter the colours below, it's probably between the varnishes instead.

Good luck and cheers,

Lussh

Thank you for your timely response.

My apologies for not being more clear, both varnishes are peeling, that is to say, the Paraloid b72 isolating varnish did not adhere properly. ​This tells me your second hypothesis is correct, when drying the umber pigments released some smaller particles and it became difficult to adhere to, though this doesn't explain why it peels from the lead white as quickly as anywhere else. In your comment, you mentioned, "wiping the painting" before varnishing. Could you please be more specific? This can't mean oiling out, I'm assuming you mean with solvent to wet the surface a bit? In this case which type of solvent should I use? I did nothing of the sort because this is in fact the first time I've ever heard of this technique, rest assured I will never forget the need to do this now. I only passed over the paintings well with a tack cloth to remove any dust. In fact, as I now think back, I was very surprised by how quickly the Paraloid varnish dried. I'd never used one before and it dried to touch dry in as little as 3-4 minutes. Which would mean it never got the chance to wet out the painting and adhere. Perhaps it would be better to use a laropal 81 varnish as an isolating coat if it has a longer open time. I will contact the manufacturer about how to extend the drying time and see what they recommend.

As regards the white spirit for removal of the varnish, will the odorless mineral spirit work, or is there something more specific that I need to look for when choosing a solvent to remove the failed varnish?

Thank you so much for your help. It is very much appreciated.

Kind regards,

Jody West