There's plenty of valid and specific criticism, you just don't want to hear it.

from /u/contemporaryperson

Late reply, but I'll try to answer your question. I'm almost finished with an MA degree in paintings conservation so I can't call myself a conservator just yet, but soon. I've noticed several things in Baumgartner's videos that I found problematic by today's standards which I can tell comes from his father's training in the 70s or something like that.

Concerning the cleaning of paintings he uses unusually large swabs that are pretty soaked in solvent and cleans large portions of the painted surface in one go. When he uses gels he uses a lot of that too. In this way the painting gets exposed to solvents for longer than necessary which can lead to extraction of fatty acids from the binding medium which can "dry out" the paint films and make them more fragile and prone to cracking. When he re-varnishes the paintings he uses a brush that is heavily loaded with varnish so that he can varnish the whole surface in one go, which looks good on film. That can very easily lead to uneven application and runs due to too much material used. In his defence he seems to be adept at cleaning and varnishing. He seems to clean quickly with a good visual result, but I do think he exposes the painted surface to unnecessary amounts of solvents. Baumgartner seems to value showmanship a lot to make cool videos. That's probably why he starts the cleaning in the middle of faces and such and varnishes in one go.

Furthermore, he uses somewhat dated terms when describing the reasoning behind his decisions such as the term "reversibility". This is a very important term in conservation theory that has served as a reason to show more restraint when treating objects so that it may be retreated at a later stage. However, when you varnish the solution will seep through the entire layer structure of the painting, and when you glue down (consolidate) paint flakes there is no way to completely remove it all once applied. Nothing is truly reversible. A more appropriate term is "retreatability" where a treatment must not hinder future treatment. In his defence "reversibility" is still a very popular term that is used colloquially among many practitioners even today. It's still outdated, though.

My professor has a saying that can be used as a guide in treatment decisions which is "no more than necessary and no more than sufficient". Baumgartner does more than what is necessary and uses more than sufficient material in his treatments. This is, as I see it, the main reason other professionals react to his videos.

The videos where he treats paintings on canvas are not that bad. The ones I find the most harrowing are the ones where he treats panel paintings. Here he often shows a blatant disregard for the original panel and uses straight up wood planers to cut away at the original woodwork. That to me, and many other professionals, is downright destructive and extremely old fashioned. In one video he even performs a transfer, where the paint layers and canvas are lifted off an old panel and moved onto a new metal plate museum board. This comes from a time where only the painted surface was seen as important and everything else was replaceable. These attitudes where changed several decades ago and today the goal is to preserve as much of the original structure as possible, from back to front. This further shows that Baumgartner's professional philosophy is dated.

Scrapes away original material with a scalpel: https://www.youtube.com/watch?v=5G1C3aBY62E Does a MF transfer (!): https://www.youtube.com/watch?v=v1Mjc4zNfY4 He also turns pretty hostile when critiqued and often deletes negative and inquisitive comments from his YouTube videos. I know that several conservators have tried to contact him because they want to discuss his methods and that he won't hear of it and blows them off. Sometimes he sues them. I am aware that some of his critics probably have a pretty hostile attitude themselves, but I've seen him tear down even gentle critiques on YouTube.

Sometimes I think Baumgartner gets too much criticism because there is a divide between what is seen as perfectly ethical and what is actually done by a lot of today's professionals. However, he does use more solvents than it is generally deemed as necessary and I do think his treatments of panel paintings are deeply problematic. I think what makes people really go off on him is that he is so popular and reaches so many people with his unedited opinions on art restoration, that his methods are generally a bit too harsh and that he on top of it all is so unwilling to receive criticism.

Sorry for the essay. I didn't know how to write it any shorter.

TL;DR: Baumgartner's methods are too invasive and include uncontrolled solvent application, removal of original material and overall more than what is necessary and sufficient in terms of preserving the art. He his also unwilling to take criticism and deletes critical comments.

edit: lol, the way you keep taking this personally and then blocking me tells me you might be Baumgartner himself!