Jump to content
Maestronet Forums

David Beard

Members
  • Posts

    3118
  • Joined

  • Last visited

Posts posted by David Beard

  1. I reduce larch balsam down to a rosin. I've added a small bit of hydrated lime putty, following an old recipe. But I remain confused about the procedure and how to judge the effectiveness of the liming. Any details on the process would be great to see.

  2. Thanks for the encouraging words!

    Good eye on the one violin. That is the first, and very much a non-standard experiment. The violin is also rather asymmetrical.

    That chin rest is something custom I made years ago. I don't like using shoulder pads, and back when I was younger and thinner I had quite a crane neck on me. This chin rest served me well. Now however, I can get along with a standard chin rest when need be.

    In that first violin, I let the build proceed very flexibly. I planned to keep the first instrument for myself, and saw it as an opportunity to get a better feel for limits and functionality in the build. The end result is asymmetrical and very free. Surprisingly, it feels relatively normal in the hand when played. The FB is very thin also, and has a bit of a maple wedge under it. Later I will restring it in gut for period playing.

    I didn't indulge in the same liberties with the second instrument, or the others in process now.

  3. It's probably healthy to remember that gesso grounds with a protein binder were pervasive through all the arts of the period. It would seem highly unnatural if luthiers of the time didn't at least make some attempts along these lines. Gessos weren't necessarily gypsum, or purely one material. 'Whites' with a 'lean' binder is more accurate.

    Such grounds had multiple purpose, including allowing fine finish and shaping of the surface, and providing even texture/absorption/tack for subsequent coats. Authors also sometimes recommended blending in a minute amount of the subsequent layer's binder in order to improve the bonding. So I guess the that means the gesso also provide an 'anchor' for the next layers.

  4. Just to be consistent with the world outside luthiery, 'elastic' has a very specific meaning which is not the same as 'flexible'. Flexible encompasses 'elastic' and 'plastic', which are two very distinct ideas. 'Elastic' materials spring back after being flexed, returning a major portion of the energy which bent them, spring steal and spruce are good examples. 'Plastic' materials flex but are deformed in the process and don't return the energy that bent them, lead and peanut butter are good examples.

    However, with varnish I'm not sure how much we are interested in a preference between 'plastic' or 'elastic'. Both qualities involve the delaying of energy transmission by investment into a bending action. I think we are rather interested in quick transmission between the wood’s motion and the air. To me, that sounds like we probably want coatings that are rather non-compressing in a direction normal to the violin’s surface, but which do not resist motion of the surface either through elastic or plastic absorption of energy.

  5. I "think" I know what you all are talking about, so I'll respond to that... If I'm mistaken, please forgive me.

    I "think" we're talking about the orientation of the bar to the plane of the ribs, not the angle of the bar as it pertains to the center line of the top, right?

    One of the advantages of working in a larger shop is observing results of various ideas and even noting results of "mistakes", all in addition to your own experiences installing bars. I've noted results I felt were "good" when the bar is perpendicular to the plane of the plate/parallel to the ribs, or the top of the bar SLIGHTLY turned in (toward the center line). I'd say too much isn't good while an appropriate amount is good. I'd also say that I haven't seen good results when the bar is angled at all towards the outside.

    These are. of course, general statements. I do often have the advantage of knowing what the instrument sounded like before the bar is replaced, but not always. On the other hand, there is often much other work going on so the results of the new bar is only one factor of the result.

    I'd also say that a bar either "works well" or it "doesn't work well". It's almost a pass/fail thing. I don't credit bars with miracle tonal improvements... They seem to contribute more to response/resistance issues.

    The last thing I'll mention is that I often install bars in older instruments with little or no "tension". In a number of cases, when a plaster cast is available, I will install the bar with the plate in the cast. Installing with more tension may well yield different results, and slightly different results pertaining to the angle of installation.

    Thank you for sharing these observations.

    What are the indications of a 'failed' bass bar?

  6. In my reading notes I paraphrased his advise as:

    The Bridge

    • advisable to powder the feet with chalk (not just for fitting, but leaving chalk for grip)
    • string height is to be adjust per player preference.
    • Joachim played with the E just under 4mm and G just under 6mm above end of fingerboard
    • A high arched violin does not require as high a bridge as a low arched instrument
    • A violin with a thin belly needs a thicker bridge
    • bridge proportions must be very particular, and according to the hardness and softness of wood, and strength or weakness of the bridge
    • If the bridge be thicker than normal in the lower part and thinish above, the tone will be clearer than if these are reversed
    • If the heart is cut smallish and highish, the tone will be harder. A large cut heart will yield a fuller tone.
    • hard belly wood needs soft bridge wood, and vice versa. Likewise tight grained belly wants loose grained bridge, and vice versa

    The Sound Post

    • post should be 6mm diameter, ideally showing 10 to 12 annual rings
    • for a thick belly, the post should be up to 1mm thinner
    • in position, its year rings must be perpendicular to the bellies rings
    • it should be of such a height as to raise the belly 1/2mm
    • the post must be placed on the belly under the outer edge of the E string bridge foot, but rest on the back 2 to 4 mm closer to the center line
    • in normal position, the post should be place the thickness of the belly behind the bridge.
    • if located differently for tonal result, the position should not be modified more than 1 or 2mm
    • a post only 1/2mm taller renders the tone sharper and thinner. If moved toward the bridge, made clearer and more acute. If moved toward the center, the G gets clearer and firmer, but the E grows slacker and softer. If moved 1mm further behind the bridge, tone becomes softer but also more muffled.
    • it is not advisable for players to indulge in tinkering with post and bridge position'
    • Ole Bull was a hopelessly perpetual tinker with bridge and post. Still author says he learned from observing Ole Bull. He would blow into the sound holes before going on stage. Saying the warmth helped the instrument speak better.

    The Strings

    • With a larger the violin, the lower tension strings should be used

  7. .... so it poses the question. "Can an instrument be manipulated by playing to vibrate in a different way or to correct a defect?"

    Bruce

    Maybe so? Along the lines of manipulating an instrument's tone, for many years I've found you can signifacantly open up a violin that has sat a little too long unplayed by driving strong disonant beats through the instrument.

    Just play some very tight quarter step double stops against the open strings. You can also play octaves, tightened or stretched a quarter tone to produce strong disonant beats throughout the instrument's range. You can easily create powerful beats.

    I don't know any tricks for wolf tones. But this is definitely a manipulation of instrument tone through playing. It can quickly open up a sleepy violin.

  8. I like sugar just fine. As you say, sugar and more often honey are many of the old recipes.

    I agree that it is optically pleaseing (enhances wetting) and has an affinity and bonding with wood, and that under the right circumstances it can be completely durable.

    I just thought some of the particle ideas about might not be so valid, at least not under common circumstances.

  9. Again I would ask, what cyrstal material could have been nanoized to that consistant of a size back in the 1700's?

    I'm not so convinced about the notion that sugar forms nano particles in water? I believe the sugar actually dissolves; a process that proceeds all the way to a molecular level -- much finer than any particles. When you get a clear liquid as the result, you have dissolved the sugar. If the sugar was still in fine particles, the fluid would be milky. Many other crystalline substances also dissolve in water. Various salts are a good example. When the water leaves, the material can recrystallize, but the crystal sizes can be highly variable.

    An example of a common material that often only partially dissolves, leaving ultra small particles in a somewhat milky fluid, would be various starches.

    In the research paper I think they were cautious enough to only state that the varnish samples show a structure which gives the APPEARANCE of having seeded around nano particles.

    Such structure might also form from the drying of an emulsion of two materials with different drying rates. The faster drying material might form seeds, which the second material then dries around. An emulsion can have many of the properties of a particle dispersion.

    As to actually production of nano particles in that era, I wouldn't dismiss the idea too fast. Levigation was a fairly common process in handling materials. This was the way to separate 'impalpably' fine powders. It really isn't so difficult to get super small particles this way. I've experimented with it just a bit.

    In one varnish experiment, I wanted to make some quite fine lime putty. What I did was stir up a bit of lime putty into the water of my little lime pit, then collected some of the resulting 'lime milk'. I then used a few stages of levigation followed by filtering and partial drying to extract a very fine lime putty. I wasn't trying to create nano particles, but I accidentally did! My fine lime putty came from what was captured in the filter. But when the waste water dried, to my surprise the residue was a strong violet color. The majority of the white lime particles were actually of the size of violet light wave lengths! If one wanted, you could collect more of this material, and then levigate even further.

  10. No I think I'm not being very clear; what I'm looking for is a thixotropic/firm varnish/medium that can be diluted with solvents. The idea is then to rub up some oil with oil and then add this varnish/medium,

    There is another line of attack for this. Emulsions are a very very complex topic, but can offer the behaviors you describe. Tempera Grassa is a conjectured classical version of this, which unfortunately never appears in the contemporary literature of the era. However, the National Gallery has recently demonstrated the presence of tempera grassa type passages in some paintings from the era, particularly in places like deep madder glazes.

    Emulsions are tricky. Here are a few things I've found helpful:

    * pigment in size will emulsify readily into oils

    * oils can easily be emulsified into water using egg yolk (just like making Mayo)

    * waters can be emulsified into an oil using a hydrated wax as an aide. (first melt a bit of the hydrated wax into your oil, then you can emulsify water into the oil) This technicque is documented since the time of Galen 150 A.D. Hydrated oils are the 'white waxes' of early art literature: spermaceti, Punic wax or beeswax treated with sea water,tallow, or beeswax modified with a small amount of borax.

    * proportion ingredients strictly focused on establishing your emulsion. Once the emulsion is established, you can add more of any of the ingredients to get the color or texture you desire.

    * don't neglect the use of fillers. particle fills can improve the emulsification process and the thixotropic behavior of the end product

    * once you get the hang of whipping up stable emulsions, they can be thinned with either oil or water solvents.

  11. compared with what is seen in most Cremonese, which mostly appear have a deep golden brown abrasion-resistant colour "in" rather than "on" the wood.

    It's very limiting to mostly learn from pictures, but... There seems to be coloring in the wood. For this reason, I'm inclined to believe some sort of yellow staining is appropriate in preparing the wood. I think Buchthorn, Madder, and Saffron tinctures are very likely candidates.

    Besides 'white grounds', artist of that time also worked with colored or tinted grounds. As Mike says, reflecting light back up and through the work was a major goal in grounds (see Cennini), but still they didn't always work from a bright base. An earthy sienna like note appears to be part of many of the classical grounds, but some seem whitish and many seem quite yellow. In relatively early cabinet maker texts, staining seems to figure prominently in any discussions of wood finishing.

    In my more successful small tests and in my first few instruments, I've used some yellow staining into the wood. I've also used a light wipe of bone black and colored earth to bring out contrasts in the wood texture.

    Using the OPs notion of a sequence of finishing goals, I:

    a) work toward a good surface texture, sealing, grain contrast, and glowing golden yellow into the wood.

    b. )then a white ground for light play. This then gets oiled out to transparent, then stained to yellow with an earth note.

    c) then a charged color layer.

    d) then a clear 'body varnish'.

    e) then a surface polish.

    Don't know what I'll do next month, but for now this is an interesting line to pursue.

  12. Hi Jacob (Kotie),

    I survived the long haul and am finally here. Not much different to Cape Town .. mountains, sea and great weather !

    Welcome to Santa Barbara!!

    If you have time, drop by the contradance this evening. Live fiddling and fun.

    The Carrillo Recreation Center is located at 100 E. Carrillo Street in downtown Santa Barbara at the corner of Carrillo and Anacapa Streets.

    David

  13. From my reading the end of the 1500's beginning of the 1600's was the period when distillation became more common and distillates of both botanicals and alcohols became widely available.

    Oded

    Exactly! This makes distillate dependant processes less likely for practices that are seen at the beginning of the Amati family's journey; but reasonably possible for processes that developed later.

  14. David, When you say vernice rosin, are you referring to raw pine gum or the liquid larch rosin you just cooked?

    That's something I have to cook for myself. I start with true Larch Balsam. 'Venice Turpentine' is generally supposed to be Larch Balsam, but most things sold as 'Venice Turp' aren't really. Very often they are common rosin reliquifid with thinner. Or often they are some larch balsam and some common rosin. So getting a good quality natural balsam is the main trick. Then you just cook off the volatile components until you have a rosin. To check, I put a drop of the cooking balsam in water and see how hard it gets. You should get something as solid and glassy as violin rosin.

    Again, this is dangerous. You have to get the temp up high enough to drive off volatiles, which you see rising off like a white steam. At the same time, you don't want to get too hot. If the 'white steam' starts to darken your too hot and need to back off pronto. Also, as your cooking progresses, you need a higher and higher temperature to drive the remaining volatiles off.

    COOKING is DANGEROUS!!!!! Even cooling your work off can get you in trouble. If you cool something suddenly, you may get violent and dangerous splatter. If you go to hot you might get fire. If you don't have good ventilation, the air around you might ignite.

    So back to topic. 'Venice Rosin' is my shorthand for 'Larch Balsam' cooked down to rosin. You can get very related rosins from other balsams.

  15. Like Joe said, varnish cooking is truly dangerous. That's the reason for the various temperature rules Jacob was complaining about.

    I'm very afraid of a cooking fire, so I take lots of precautions, watch stiring and temperature closely, and always proceed as if the worst that could happen will happern.

    Also as Joe said, I tend to cook small batches -- partly to keep the risks more managable.

    I keep my cooking very simple. First I make a rosin by driving off the volatiles from Larch Balsam. Then I carefully cook together sun thickened linseed, mastic, and my 'Venice Rosin'. I do the thread test and that's it. I keep cooking at as low temp and short time as will get the job done, because I don't want my varnish to color or go dark.

    I don't use any spike or turp spirit or alcohol in my cooking. For one, thery more dangerous to heat. Second, you'll mostly just drive them off anyway. I just heat the oil first and slowly add the other ingredients in crushed/powdered form until they incorporate.

    My varnish is super thick after cooking, but I thin durring the cool down with spike.

    I'm inclined to believe that Marciana and similar old recipes are refering to rosins cooked out from balsams. To me that seems more natural and consistent to the period than any other explaination I've heard or can think of. Also, I tend to believe when those early text don't say "SPIRITS OF turpentine", then they don't mean "spirits" -- what we commonly mean when we say turpentine. I rather think they either meant the balsam or the rosin, depending on context. IMO

  16. David, thanks for that info.

    When do you add the spike to the varnish and how do you measure amounts ?

    Cheers.

    I stick to simple (and rough) proportions in my recipes. So I don't really measure beyond eyeballing things like 1to2 versus 1to3 versus 1to10, etc. Beyond that, I use Spike as a thinner. So once a recipe is prepare, I just add more as needed until I have my desired consistency. Considered that evaporate solvents are always coming out as you work, what is the point in trying to strictly control this moving ratio?

    Also, many of the same resins that desolve in turp spirit will disolve in Spike. But you have to test. There are some exceptions.

×
×
  • Create New...