robertdo

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About robertdo

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  1. Yes but what if Guarneri was actually a fan of Mark/Schon violins and kept some in his basement as investments?
  2. I think that authors give away their copyrights to the publisher for a certain amount of time. So I would think that even in case of death of the author, the publisher has latitude to give permission for pictures reproductions
  3. You know you only have to mix NaOh with water at 10M (about 40g for 100ml of water) in a falcon tube to discover what an exothermic reaction is. I had to do it few time, and after 1 min or 2, you can hardly hold the tube in your hand (means temp increases above 50C )
  4. this "dark colophony" is not really that much darker than the usual colophony. Cooking inside a wood stove could indeed be a (funny) way to cook rosin. But to honest, reading this thread makes me feel like people are dealing with atomic bombs. I mean when you melt 30g of rosin at 100-200C on a large container on top of a heating plate in your garden, what kind of cataclysm can you expect? We are not talking about kilos of rosin cooked at 500C inside a non ventilated area with tens of kids running around.
  5. If I understand what I read, the black iron oxide is formed when oxidation of the rust is stopped. Does it mean that this black colour is due to the varnish part becoming less and less permeable to oxygen/water?
  6. Would you get the same result if you were to test the same violin with several different strings? And do a Stradivarius or a Guarnerius sounds the same if it is played by Kogan or by Menuhin?
  7. If we're to believe Dr Who, don' t close your eyes when you look at this angel...
  8. I think that would be the start of 20 pages of pretty useless discussion since you will find as many opinions as there are participants and in the end no one will agree with anyone...
  9. So how is your madder lake making going? Did you try again?
  10. No really more information. I just saw this small video on the french news. http://www.lemonde.fr/culture/video/2014/04/04/un-stradivarius-pour-45-millions-de-dollars_4396093_3246.html they say they expect even more than 45 millions.
  11. People seem to brace themselves for a new record at the auction of the Stradivarius MacDonald viola.
  12. I mus stay that the first picture doesn't show the right colour at all. It should be much much redder, a real deep red. It's strange because the picture you showed earlier in the thread seemed red. the problem comes from the lye solution I would say. Also after filtration there should be no particules left in the madder/lye solution. It seems that you still have a lot of debris.
  13. the strange thing is that once the madder alizarin is dissolved in the lye solution it becomes very red due to the basic pH (and it looks like it's really red on your picture). Precipitation with alum should not change the pH enough to lose this color. Do you remember if the color was still red when you added the alum? Did the color fade afterward?
  14. the colour looks right in the lye solution. After precipitation in presence of alum it should stay that red. Yes, 10g in the volume of varnish for 1 violin is too much. I can't give you a number but the best way is to experiment. What was the molarity of your sodium hydroxide solution?
  15. when you soak your madder roots in the lye solution it should immediately turn purple red. If it was not coloured at that time then there was already some problem with the lye solution most likely. you don't add 10 g of madder lake to varnish 1 violin...