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Mike_Danielson

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Everything posted by Mike_Danielson

  1. Transtint dye in black. Dissolve in alcohol. Apply multiple coats until black enough. Then french polish
  2. They appear to be metal pins which means the glue joint is weak between the pins and the wood. This is not the way this tip repair would be done today, and it violates all the modern rules of repair since you want the reinforcement to be as close to the tensile axis as possible to prevent the crack from re initiating. As is said. "let sleeping dogs, lay." I cannot see the glue crack; so, the crack was correctly closed and the evidence of a break gone except for those pins. Without the pins, you would not be able to know there was a repair--which points out the danger of buying a bow with repairs well-concealed. I would play it happily until there is an accident and the crack reopens--then it can be repaired again in more modern ways (but probably without the metal pins which would be removed) Mike D
  3. As I recall, this was a piece of clear packaging tape applied to the side, near the neck. Since this is on the back, I do not recall a fix for this using tape. Does he want some restoration of the varnish or just protection? That will determine what to do next. Here is a simple idea for just the finish: use an air brush to spray shellac over the area. Now here is the trick--put the instrument in the UV box and subject it to overnight UV treatment. This will set the shellac. Repeat as needed to get adequate build. Shellac hardens under UV and gains wear resistance. Can be repeated indefinitely. Your choice as what type of shellac to use, but for maximum wear resistance, use dewaxed. Mike D
  4. I insert a 1/2" dowell in the neck/root of a new cello. You can set the overstand on the button--this dowell stabilizes the neck. AS far as wolves on A and D, look for the resonance region on the treble side of the instrument. If you use a Krentz unit, insert it below the soundpost and experiment with the position. The wolf is probably on the G-string as well---fix that with a weight on the afterlength.
  5. Difficult to know where the problem lays. Contaminated varnish? Contaminated violin surface? Maybe the work bench is contaminated. Strip the finish off and start again. Test the ground and varnish on another piece of wood--multiple coats before going back to the instrument. May have to toss the varnish. Shellac cures all problems. Wash your hands before working on the instrument. I had this problem (fisheye) on a piece of furniture--my response was to immediately wipe the finish off before it had dried using solvent. Gave the surface a quick wash coat of shellac, and "Bob's your uncle", the problem went away when I recoated it. Mike D
  6. John, it looks like you killed the conversation by introducing some useful technical information. I appreciate your efforts. For those who do not want to read the technical paper of Tirat, let me mention that she has found about 400 varnish recipes over 3 centuries of varnish data. These recipes have as a fundamental characteristic a composition of a drying oil (linseed) and colophony. She includes detailed recipes for 12 in her paper. So, it is pretty well established what these historic varnishes have to be. And a reasonable composition (but it does vary all over the place) is equal weights of oil and colophony cooked to a very high temperature. She could not go above 250 C in her laboratory. The varnishes are thixotrophic which is very useful if you brush.
  7. The quotation comes from "The Wolf Man" movie of 1941. The old gypsy woman foretells what will happen to Lon Chaney, Jr. I left out the part about when the wolfbane blooms he will turn into a wolf and kill. Mike D
  8. Varnish making is simple and inexpensive if you use a recipe like Hargrave's. Cooked flaxseed oil with a resin (colophony, for example) has been used for centuries, and they have a known track record. See Mrs. Merrifield's book. The uncooked rosinate varnishes like Michelman's are a failure. This is well established. The long term performance of cooked rosinate varnishes is unknown. And I suspect they are very hard (not as flexible) as the Hargrave-like oil varnish. Long term stability of the color is also an unknown--all that iron in the iron rosinate could be a problem, and use of madder has a well-known problem with color stability. I would worry that the varnish will eventually alligator or breakdown as in flaking. ASTM has published methods for rapidly testing varnishes for long term performance--this should be done to this new type of instrument varnish to help establish some kind of confidence. But maybe, because you guys are "pure of heart and say your prayers by night", these potential shortcomings will not occur. Mike D
  9. I am curious--what is the recipe? Mike D
  10. On the rare occasions I make this repair, I use a knife to score a cut down the center, widen it with a very sharp edge triangular file, followed by a narrow hand sand, followed by a wider hand saw. I use a wood of close annual rings--sometimes cherry, sometimes maple. I have used elm, a wood that is supposed to be very split resistant. The watercolor box can help hide the repair. The reason you have the grain cross the tip of the break (like Rico shows) is due to a fracture mechanics principle--you must prevent a crack from ever initiating. Rico, I wish you had gotten the crack to close tighter. Mike D
  11. Thanks for the information--the first time I read this, I was still in my cradle.
  12. Cameron, make your own stuff--it is simple. Follow Roger Hargrave's bass book recipe but take it up to 300 C; so the process is over in 1-2 hours. Time is determined by the color density you wish. You will get a red-brown varnish in any case. This recipe is a variation of the recipe in Mrs. Merrifield's book which goes back a few hundred years. Long term experience is what you have to depend upon for long term stability of the varnish. Add turpentine to thin and a few drops of Japan Drier before application. If you look at issues of The Strad magazine of a hundered years ago, you will find venders for Strad Varnish. These suppliers are long gone--wonder how that warranty held up. Watch out for cold varnishes--they resemble megilp which is famous for its ultimate failure. If interested in varnishes, look at the data on what oil painters have used over the centuries--They are the ones with long term experience on how this stuff holds up. By the way, ASTM has methods of determining the stability of coatings, varnishes, pigments, etc.--none of the modern violin varnish has been subjected to this testing for stability; so, it is all a guess. Mike D
  13. Brown needs to give us more information. Something gave it a deep gouge and then there is some dirt in the bottom. Anyone's guess--cryptic from the OP. As far as the varnish is concerned, this is what happens when you put too much pigment in the varnish--muddy.
  14. LL1985---I had this problem on a cello I made. It was a copy of the Andrea Amati of ca 1550. Wolf at F on the A-string was not controllable with the usual methods. The usual method being if you can control the wolf on the D-string, it will disappear on the A-string, but this did not happen. Here is what I did to solve the problem: I use a Krentz-type eliminator, but I put it on the Treble-side of the instrument about 8 cm below the f-hole. Note, this type of eliminator is normally used on the bass-side. There was still the usual wolf on the D-string but a brass thingy on the D-string afterlength took care of that. I use 35 grams of rare earth magnets as my version of the Krentz eliminator. I buy magnets that are 1/2 inch in diameter but at a couple of different lengths so that the smallest magnet is on the outside to hold the thing in place. And I use some cork on the outside magnet to prevent varnish damage.
  15. Rehaired a Glasser carbon fiber bow the other day. It had a plastic frog. Thought about this for a while--used one drop of medium thick superglue on wedge. I use hide glue on wood frogs. Mike D
  16. Give it a french polish. It will fill the scratches and give the right level of warm shine.
  17. Martin, I can understand how I accidentally "backed over" your red wagon since selling/buying old bows is part of your business. There is nothing easier to rehair than an old French bow that is in good shape. My problem is that some of them have been "ravaged" by earlier rehairers. The restoration work is too expensive for the owner, and so you try to do the rehair without doing further damage. It is a limping along. I do not do restoration work on frogs or on the lower stick end when there is a split or excessive wear. I send that work on. Mike D
  18. I read Espey's comments that nitric acid treatment is a surface effect; thus, it has no long term effect on strength. But it is just his opinion. I take no comfort from his conclusion. I am a materials scientist, and I would like to see some numbers on strength as a function of time. I have seen a violin which (apparently) had spruce top treated with nitric acid--the sign was a very dark brown color. Built around 1930s on the one I worked on, the wood was so weak you could poke a finger through it. I am going to do some work on this topic. Mike D
  19. I would suggest that you purchase a modern bow based on the playing performance. Forget the old bows. The old French bows have been treated with nitric acid to make them that a nice dark brown color, and I suspect the degradation of the acid treatment has weakened them. I have rehaired a lot of these old bows, and sometimes, they scare me. They can be good players and still fragile such that you can damage it. Significant, old repairs can be extremely difficult to detect. I can understand how an experienced person can miss them. What I say is not going to deter most people. Then, it becomes buyer beware for the old stuff. I am also troubled by the problem of identifying the old bows--it is so easy to make a mistake since there are not a lot of significant features. Mike D
  20. Thanks James and Violadamore for bringing this paper to my attention. I read it a couple of times. Yes, adding pumice and/or bone ash have a very beneficial effect on speeding up the drying but it is not any faster than adding lead driers--this is useful to know. The big surprise for me is that their analytical techniques were applied to over 30 different musical instruments. And the varnishes all had a similar composition--all based on a drying oil and resin from pinacea treas. This is additional confirmation of the work by Echard and many others that there is a consistency to the resuts. The particles in the historic varnish seemed to resemble pumice. Since they found phosphorus, that seem to be the driving force for thinking bone ash was added since that is a possible source. I suspect it could also be a contaminant that is present in the pumice, rock, or whatwas added to enhance the varnish coor. When the authors made there own varnish, they reached for linseed oil and pine resin. Cooked at 220 C for 6 hours. The varnish was extremely light colored. We know from other outside data that you have to cook it at a higher temperature if you want a dark red-brown varnish. The authors took a look at historic varnish recipes before they made their own; such as, the De Mayerne recipe and Strassburger manuscript--they did their homework. Anyway, I like the paper, and as time goes on, we will get an even better understanding of what the masters (there were a lot of them) were doing. My surmise is that it will be something simple and practical--no secrets. Mike D
  21. Roman, give the customer what he(she) wants. No lecture. Here is how I would do it: 1. Seal the wood--I would use several coats of dilute fish glue. 2. Use your least colored varnish varnish and put enough coats to completely seal/fill the wood. Rubbing on is probably enough. Your goal is to not allow the black to penetrate the wood surface. 3. Get a can of black spray paint of your favorite black. I would go with a semi-gloss. Mask off what should not be coated and put on several thin coats until color is uniform. 4. Finish with 2-3 coats of you least-colored violin varnish. For the neck, I would use black Transtint dye followed by french polish. I like these types of problems Mike D
  22. This product from Kremer is essentially pine resin or rosin dissolved in turpentine. You could make your own or even dissolve rosin in alcohol for a similar product. In any case, the solvent evaporates leaving the rosin behind. Some varnish makers offer a balsam ground which is probably similar to the Kremer product. In the short term, it is not going to dry by polymerization like an oil varnish does, but it will appear to be dry to the touch. Better try it to see if you like it. It would probably work as a substitute for sealing the bare wood by use of a protein such as glue. There is a lot of analytical chemistry work that suggests a protein sealer was often used. Mike D
  23. I think the world is ready for a new cello case design. I am talking about one that protects the instrument from the neck snap when the case falls over.
  24. Jackson has an extremely high regard for the varnish book by JG McIntosh. I looked in the book and I can find no instance where he makes an iron rosinate--that is strange since it is such an obvious thing to do. The rosinates made using cobalt , lead, and manganese, for instance, are used in small quantities as driers. Mcintosh makes mention of a cheap varnish using some kind of rosinate--I cannot remember the metal ion used as the rosinate salt. I cannot find any reference in the varnish making literature where the entire amount of rosin to make a varnish is presented to the linseed oil as a metal rosinate salt. In other words, the varnish is a cooked metal rosinate with linseed oil. I do not know the significance of this difference, but it is greatly different from the traditional making of a cooked oil varnish. Merrifield's recipe calls for only a small amount of alum to be added (size of a nut). My suspicion is that the rosin combines with the linseed oil by esterification during the heating process. With a standard rosin and linseed oil, the ester releases water which just evaporates from the hot liquid. With a total metal rosinate, a calcium hydroxide, zinc hydroxide, sodium hydroxide etc (it depends on what metal ion is used with the rosinate) is left behind in the varnish. I do not know if that product will continue to react with the varnish and have some later, long term effect. In particular, will the iron rosinate be color stable over time. ASTM has methods of testing varnish aging and color stability. I think you have to be very careful when beating the drum for a new method of varnish making that may have future problems. Be careful. Remember megilp and its dreadful effects. The initial response for megilp was enthusiasm. You can still find people that like it. I think Michael Darnton likes using a varnish for violins that is megilp--but maybe his thinking has changed. Mike D
  25. Rosin or balsam as a ground is not the same as linseed oil. At least linseed oil will harden as your chest of drawers shows. If you are using the rosin or balsam in small amounts as the ground, then why not use varnish in small amounts as a ground because it will fully harden in a short time. The refractive index is probably about the same for all these. Mike D
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