Sorry, I meant "completely organic" like the egg white mixed with salt.

Some guys like Damar, I personally think that it yellows too fast, but other guys haven't experienced the same problem, I think that's due to climate differences, it is very humid here in Brazil.

Hope everything will be okay with your experience now.

I think we might start another thread about damaged paintings, but here's an example about the Mona Lisa.
Her portrait was painted from 1503 to 1506. Raphael loved the portrait, which was much different from the one we can see today, and he did a sketch in order to use the pose. In his sketch the woman has eyebrows.
He borrowed the pose to do Maddalena Doni's portrait.
Both women have eyebrows and you can see eyebrows in Da Vinci's work too. The point is that many of his paintings seem to have been damaged by restorers, not only eyebrows, but clothing details and skin color too.
So, as we can see, it was not a matter of fashion.

Claudemir, thank you for the information! I had no idea that you could make a varnish out of egg white and salt. I know that eggs are used in egg tempera but I have never personally tried it.

Did the masters of the Renaissance use a final varnish?

Yes they did. There is an entire section on varnishing in Cennino d'Andrea Cennini's book "Il Libro dell' Arte" published in the 1400s. Early varnishes were often done from amber or mastic or copal, and sometimes by mixing a solvent with a balsam such as Venice Turpentine. Damar/dammar varnish has come into primary use in the past 100 or so years.

Michael is right.

Egg varnish was widely used because it was a lot easier to prepare then the other ones. The removal of egg varnish is done with a moistured rice paper applied on the surface of the painting, and then it is removed and the surface is cleaned with cotton swabs.

Thank you, Michael! Do you think they intended for someone to remove the varnish to clean the painting or is that something that was developed later by conservators?

That sounds like it would be less stressful to the painting than solvents. How come eggs don't go rancid?

I still don't know what Michael is about to say, but they used the varnishes for the same reasons pointed out in this thread, protection, sunken areas, etc...

Because of the salt.
I tried it more than a decade ago and the painting still looks fine.

Thank you for answering my questions. Why is it best to avoid organic varnishes like the one made out of egg white and salt?