HoGo

I agree that the main problem may be in distribution of forces against the plastic "dam".

After reading some sources and digging into my memory I'd expect they used common recipe of nitro lacquer after end of shellac. Those old nitro lacquers often contained other resins and shellac as well besides that nitrocellulose so the blend had desired properties (hardness, elasticity etc) Spruce rosin has been common material used in many industries and varnish making till fully synthetic resins took most of the uses. I still have a bag of old rosin from 70's or so I found on grandfathers attic (he used to work at chemical plant producing paints so I guess that is where it came from) My suggestion would be first test sample for color in lacquer itself - srape minimal amount from thicker bead and notice if the color is still there or the spot becomes lighter colored which would indicate color in fininsh. When you get past the finish you may notice whether the color sits on the wood surface or just below or is soaked deep that would tell you about possibla stain - penetrating or thicker one and it's color density. For re-creation of the lacquer you may look for MSDS of simple nitrocellulose lacquers - I'd not look into best modern producers but rather obscure producers from third world who may still be closer to simple old school lacquer and parhaps try mixing some rosin dissolved in acetone and perhaps bit of shellac or dark cooked rosin (like many makers use for violin varnishes) for extra color. You may try to make your own nitrocellulose lacquer from pure nitrocellulose (available on internet) by dissolving in mix of solvents (acetone etc. depending on desired speed of drying) and adding bunch of other resins and plasticizers it is not different from simple spirit varnishes that violin makers make. Of course the chemicals may be dangerous for your health so take precautions.

WIld pear is quite common in central european region and can grow to large size, It was prized also by woodcarvers so I think it was available to trade in most parts of europe. I know od one wild pear within 2 miles from me that is way over 1 meter in diameter and almost 30 meters tall. Another one I know is around 1m diameter and the trunk is at least 7 meters long before it splits into branches. Both trees are very healthy. Orchard trees are common source of pear these days but they are small as fruit growers prefer smaller grafted trees.

Unless the pics were calibrated and your screen is calibrated too, you will always see only aproximate colors.

To me it looks like student grade german/czech 20th century violin with plain maple back. I'd guess between the wars?

Ideally you use weigth that equals the tension when the bow is played and at 50% RH. Or use unicorn hair :-)

Find a new teacher. Teacher doesn't necessarily need to know every detail about construction of instrument but this is vital for good playing and teacher who doesn't know this and even prevents the correct setup for student should not teach at all. Muscle memory will thank you for getting the board setup correctly.

You can pre- stretch the hair by tying a weigth to it and let it hang for a while on a nail. Mark the starting position on the wall to check progress. You may wet the hair slightly to speed upp but some bowmakers may be against wetting hair. This was common technique of traditional bowyers (archery) when they used bowstrings made of sinew.

Actually he doesn't mention plate at all, he says kinda rhetorical question "how you bend wood and shape it and glue it under pressure... " that agrees with simplified process of making. You bend wooden ribs shape plates and glue it using pressure of clamps I don't hear any implication he is talking about plates exclusively.

Too bad it only goes to 93 degrees C....

I do build mandolins but arch top, not flat top and do not know anything about this maker but the first view of the violin screamed autodidact or first instrument of violinmaking student before he started school...

Sorry for side-tracking. Are you sure it wasn't nitric acid? Or alien blood? What was your violin varnished with? Dry oil varnishes are generally quite hard to dissolve with common solvents and solvent based "spirit" varnishes still take a while to dissolve even when hit with straigth alcohol or acetone. Mineral oil (which is major part of the Lemon oils) is quite benign and the worst I can imagine would be a hard-to-clean oily spot if it landed on bare wood. I've used mineral oil as lubricant for french polishing for two decades and it doesn't attack alcohol based varnishes at all.

I'd guess they thinned the ribs to thickness they could comfortably bend and which would be still strong enough. On cellos they knew the thickness is just barely enough so added the linen prevents cracks thay knew from older instruments.

Yes, the angle changes a bit. If you assume the stick is landed 15 cm from the blade and the spacer wood is 2cm thick and his movement range is approx 1cm, the angle change is around 0.5 degree. Many of the simpler jigs likely won't give you much better tolerance. From my experience the wood doesn't see what's behind the very edge of knife (it's microbevel) unless you are using some kind of chip breaking technique or use it like flat chisel (but for that single bevel knife or flat chisel is best). If your micro bevel is right for your application and steel type you don't have to care about that. I don't have grinding wheel and always rough sharpen at more accute angle so my final micro bevel at the very edge can be any angle I like. The only advantage of hollow grind is that you can lay the blade on flat stone that bridges the hollow ground sdge and allows easier control over angle (which is dictated by the original grind angle) while being honed. But you still have to take away twice as much meat during honing as if you only touch the micro bevel and you can only go to more obtuse angle from the starting grind.

You can use a wrap with thin silk but since the grain is running so angled through the whole end of bow visible in the pic you can expect new cracks start sooner or later anywhere in the unwrapped area. The owner and restores should decide what is worth doing.