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David A.T.

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Everything posted by David A.T.

  1. I did not find 1/12 octave analysis free or cheap software. Most seems to be professionnal such as the ones used in acoustic Labs. Maybe Audacity will develop these options in the future. Only a 1/3 octave available here :http://www.ymec.com/hp/signal2/index.htm But I the think 1/3 is too rough. On the other side full spectrum as is doing audacity is confusing in high frequencies (my opinion). Then I make a record with Audacity and apply a 1/12 filter with an Excel file. I you want i can share the file with you and you can try to compare few records. I can also convert to google sheet and share it .Let me know.
  2. I seal both. For same reason as explained above.
  3. To the OP question. I had many issue to understand the acoustic charts from Violins papers, mainly because I found the high frequencies very confuse. Then I am dooing some records at the moment and applying a 1/12 octave filter. The steps are 1.Record a Note with Microphone - exemple above is a "B' done with a Bow on a Cello. 2.Extract the Audacity data (I use 8000 values) 3.Make a 1/12 filter done with xls file (a bit tricky xls file at the moment) 4.Do the same with a good record : I picked up a 'B' from a Strad on a record. Then compare. Don't know if it help in the discussion but I think it is the good topic to share it. I find the harmonics easier to compare
  4. I thought it was pieces of wood inserted, but maybe it is just some tape in fact
  5. it Looks nice. I though shellac was not compatible with linseed oil coat varnish.
  6. I was looking at the cello when I noticed the reinforcements in the bridge. Is it something commonly used with proved efficiency ? https://youtu.be/ysanMdsLhQM Note that there is also a wolf killer with 2 springs
  7. He' s wearing a red jacket and handle above a red carpet. It helps much to get red reflection with a gopro in the back. I personnaly have a mirecourt with red varnish. Light on right Light on left red in both angle. No Dichroism exemple.
  8. It can be found in the Capitel 495 from Collectanea-Chymica-Leydensia-Maetsiana-Margraviana the receipt (Edition year 1693): Maybe someone can find even older evidence of the process.
  9. I just took a look in Bonnani's book from 1723. here is one of the receipt of the italian varnish : take 8 part of Turpentine, put on fire till it reduce to 1 part.... The current usage is not so far. Note : no (washed or not washed) linseed oil in this receipt. then old evidence of cooking the resin at high temperature could be inside this book (1693) : https://www.amazon.com/Collectanea-Chymica-Leydensia-Maetsiana-Margraviana/dp/1166677524 while it is decribed as a text in Latin it is actually in german. https://play.google.com/books/reader?id=Lbc5AAAAcAAJ&pg=GBS.PP6&hl=f I will try to find the corresponding extract.
  10. The Strad published an article. It explains in few pictures. Put oil in a bottle, put same amount of water. Shake. Wait 24hours. Then 3 phases show up. Only the top one (oil) must me used. The middle is wax, the bottom is water. In my first project I did not perform this step. Maybe it explains why my varnish seems sticky. I wonder how to remove wax or to correct it once it is applied.
  11. Quick update : so far I am happy with the chamber. I added a 100w black light (60+60+100=220w total) the temperature is still acceptable. I will maybe buy an other 100w ( to get 320w). Then it cost a bit when running during severals weeks ( but not much in regards to the instrument) The driing time seems to be same as if the cello is behind a window but the big advantage is to be free from dust. it requires 1 m square place thought. the chamber is cheap, lamps are not cheap. I have no idea if the small lamp as asked above work fine - their function seems to be heat production. The big led panels have ip66 Label which for sure contribute to their cost.
  12. You don't and any focused and interesting discussion is welcome.
  13. True, I did not use your technique. But now I focus on cooked varnish to understand/see how it behave.
  14. I don t use liquid Damar. Yup, this is the case, I use raw resin piece. Kremer oil and Damar cooked together : which is a lot différent thant the result I got with 'cooked oil' from the shop. (First pics of the post)
  15. I read following books: Sacconi, Tolbecque(with lot of old receipts), Padding, Harmmel, Beament, Fry, Michelman, your article, M.Darnton's notes. I used Sacconi with propolis but had to redo the instrument because it was too soft. I used Michelman but failed because too long to dry and color fade (I don t want to retry these receipts), I used one of Milans one but color was not enough also. So I am still looking for how to make the dye (from madder / cochineal) not fading in the oil/resin. The only way I managed to keep the color was when I use alcoohol. I also bought oil varnish from Harmmel but would prefer to prepare one because I know what I put in it. I also view the strad articles how to make mineral dye (precipitate) and mix ot with the varnish before application. This way I did not try yet though. I would like also to avoir to cook above 200°C for safety reasons . I don t have equipment to keep stable temperature. I think you mean cooking rosin at high temperature when you say 'proven method' . Is that right? I am experimenting simply because in all these book there are plenty of options that let the reader chose its own way. And when having too many books, receipts, opinion (good or not) finally one can get lost. I think I am not far from something stable. Note : finally the Kremer oil drop dried through the window, but it took 3 weeks.
  16. I was also thinking to the pH. Thanks. I think I will continue my experiments. I don t want to bother you though. Was just asking a question.
  17. I took some of the Damar/oil mixture and mixed with cochineal dissolved in water. Then i heated during about 6 hours at 120°C to evaporate nearly completely the water. It leaded to the red/violet color on the left sample (one drop I spread with finger). But as still some bubles were showing presence of water in the mixture I did the bowling 2 hours more at 120°. Then it turned to yellow/Brown, sample on the right. Do someone has an explanation : did the cochineal burned ?
  18. Hello, High temperature but not too high and not too long, is that right?
  19. Exactly the issues I had. Wind, dust, and when it requires several days/weeks it becomes a nightmare.
  20. I put a plate with one coat oil varnish 10 hours in it. But it does not seem to dry faster than a second plate I put outside. - I can look for 2 spot more. - the plate is in the middle at 50cm from the spot . Maybe too far . - would a smalll fan in the chamber be usefull to bring more air on the surface ? to compare, for nail varnish they put 168watt very close to the nails. So it makes locally lot of energy.
  21. Understood, it is my sandbox.Decision is easier to take than on a cello made by someone else. Considering above answers I will not go further.
  22. Many reasons : wanted to change the tailpiece (ebony gewa i don t like it), wanted to reduce the fingerboard width by 1-2mm (my first cello, I had many uncommon and not convenient dimensions). Maybe soundpost change (1.5years old). 3 pegs to redo because they were becomming too shorts, holes were too large...and then it was opportunitty to try to kill the wolfnote. It is also opportunitty to better understand how all parts react together. This vidéo shows how i built it.: At 2:58 you can see the bass bar. I know now that I made it too weak. But the cello has à nice tone that I like . Just this wolf note is the issue.
  23. Really? So far I am the only one to notice the wolfnote on the cello. Then maybe I don t play it too bad .
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