CSchabbon

Depends all on how wide the strips are. If they are not wider than the thickness of the top, there should be no problem. I don't really think that cleats are superior to silk strips or woven polyester, especially if the cleats are thick and there are multiple cracks. I can see a problem if there is a wide strip of parchment, those sometimes come loose. Also, a lot depends on how good and strong the glue is that was used to glue the cracks. I have seen repairs that were probably 100 years old, still pretty much invisible and sound.

It should be clarified that there are a number of different alcohols. Ethanol should not be compatible with oil varnish, however Isopropanol (or isopropyl) should mix well. I cannot see any advantage of using Isopropanol over turpentine.

Why not use a respirator?

This violin is at the end of its useful life, it has salvage value or in this case maybe no residual value. It would be better to guy a reasonably priced instrument from a local shop. The local shop usually guarantees the availability of repair (if it's not a general music store). If you buy a violin from ebay, you might end up finding no one who wants to repair your violin. In this case, the post repair value will be lower than the repair cost. In other words, on every dollar you pump into the repair, you get pennies back.

I'd rather doubt that you could get $100 on ebay for it. I also don't believe that it would be worth much more once repaired. It has a soundpost crack in back and top. It will make a nice campfire though.

My favorite pigments for retouch were the Cinquasia Pigments from Kremer. Here the link to the red: https://shop.kremerpigments.com/en/pigments/pigments-of-modern-age/organic-pigments/4810/quinacridone-gold-red-gold-po-48 Unfortunately they don't have the Cinquasia Gold (Gold-braungold? PO49?) anymore, that was my favorite yellow. The Cinqusia Gold-rotgold is a perfectly pure red. Those pigments were so fine, no grinding needed and perfect transparency. I still have two jars of W&N Indian Yellow left, but I always thought it to be too opaque. It will probably still sit in my pigment box once I am dead. The Orasol dyes are and the Hammerl "Farbextrakte" are the same thing btw.. I have used them with mixed success. I stopped using them completely. All except one of them really change color under whitish fluorescent light (the red becomes invisible somehow), also the tend to mess up the flow of the varnish when brushing. It's a pity all those nice pigments get discontinued, I think those big chemical companies (BASF probably) make a batch every few decades and once exhausted that's it. I would and will look into Quinacridone pigments. I think that's the way to go. Also, Artemis makes excellent lake pigments. Probably the best, they just have so much experience. They do need a lot of grinding though. Here the link: https://www.artemis-pflanzenfarben.de/index.php?ccPath=11

Where did this wood grow?

I glue size the wood right before adding any filler, then after cutting back size the filler with thin shellac as you said. Seems to work ok so far. I recently switched to using Schilbach's unversal Lut for glueing on the top, that is by far the weakest glue I know, I would not use it for anything else. My glue-water ratio is maybe 1:4 or 1:5. The best filler is in my opinion a CNC insert, glued with strong hide glue (like Bjorn 192), more like 1:2 or 1:2.5 ratio.

That must have been a fast worker if he managed to mix the bondo, slap it on the top, add the linen and clamp it all on the ribs in only 6 minutes! I'm impressed.

When I learned furniture making in Germany the guild system was still in place. An apprenticeship was 3 years long. Pay was very low. There was an exam after three years, where you had to build your journeyman piece. We also had safety courses for operating machinery. The was a state exam. Then you would have to work a few years (I think 5) as a journeyman before you could try the Mast exam. Most guys would do a year long course, some evening and weekend courses. It was extremely expensive to become a Master. Without a Master degree you could not open shop. That would mean the level of workmanship was very high, since every shop owner was properly trained and had to have many years of experience before he could open his/her shop. There was less competition for established shops, probably prices were also higher, but quality was pretty much guaranteed. Since then thing have changes, since Germany joined the European union the whole system is different, and you do not need to have a Master title to open a shop. I imagine the guild system was even stronger a few hundred years back.

Just what Jerry said. in at least 98% of cases original and polish are interlocked and inseparable. It's not that the new layer just sits nicely on top, it has melted and mixed with into the original, into all the crevasses and nicks and craquelure. The only way to get it off without removing big parts of the original is a lot of patience and many hours. Scraping with a scalpel is the slowest but safest method.

Also, in my humble opinion, shims really don't work on old instruments where the contact surfaces are not even. Except if one customs fits them, but in that case I usually make a new bridge.

Also, the bridge shrinks and expands with changing humidity. It's about 0.75-1 mm difference in height change from 40 to 60% humidity.

I don't get this. I have 2 Luxo LS1 long arm at work, and one at home. They have one problem, the screw that attaches the screen to the arm can come loose, so I had to tighten that few times. Otherwise they are by far the best bench lamps that I know of. I have had them for many years without any major issue. They are on Amazon, and returning should not be an issue.

I have been experimenting with glue a little in the past few month since there seems to be very little knowledge in the common pool. It takes quite a lot of energy and time to test different glues, glue to water ratios, and types of wood, so this cannot be stemmed by one person alone, but I have glued and broken quite a few joints. There are many other characteristics glue can have; viscosity, surface tension (or how glue can creep up cracks), melting point, gel strength, bond strength, sensitivity to bacteria (longevity)... My main conclusion about gel strength is that there seems to be a negative correlation between gel strength and bond strength, meaning that the low gel strength glue I have tested have usually resulted in a stronger bond. Or very simply said glue joints with glue over 300 gram strength came apart a little easier. There is a big difference in glues from different manufacturer, so skin, fish or bone glue etc. cannot be compared easily, as well as gel strength, although there seems to be a trend. High gel strength glues seems to be suitable for glueing patches (less penetration in the wood, so a thinner glue joint, meaning less tension and less distortion in the plate), and ground preparation/isolating the wood . Low gel strength had generally a stronger joint. To achieve a reasonable viscosity, high gel strength glues usually have to be diluted a lot for difficult jobs, resulting in a weak joint, so I try to avoid them for anything that has to withstand a lot of force. If the gel strength is extremely low like in bone glue though, the glue might penetrate to deep into the wood, also resulting in a weak joint, especially with a high water to glue ratio. Since there seems to be a strong correlation between gel strength and viscosity, it seems to make sense to use low gel strength glue for difficult jobs, like glueing cracks, or jobs that need more time like glueing a top. For spruce center joints I would not recommend the highest gel strength, but a low glue to water ration (low gel, thick glue!!!), also since glueing is pretty straight forward. For maple a thick bone glue might be the best option