Dominik Tomasek

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Posts posted by Dominik Tomasek

  1. Dear Maestronetters,

    reading the topic gave me this thought: How come do the 5 string violins play with it's "short" stop lenght/mensur? I do know that the dimensions of these instruments are sort of restricting the dark viola like sound but to my logic it seems that the problem could be, at least partially, solved by making the body a bit wider and the ribs higher. 

    Couldn't this be the way of stringing the small violas? Keeping the stop lenght shorter and using violin C string? 

    Sorry if I mix things up I just share what comes to my mind!   

  2. 9 hours ago, jezzupe said:

    to further point out my hypothesis, if we look closely at the first pic that is showing the blisters, we see that every single one of them is either on the more open porous spring growth line/delineation,or right next to a line,... and the effect on the back as the maple has different grain than the front, it is showing as more of an uneven orange peel'ish texture , some of which seems to be from application, and some from the under coat being not quite dry...imo

    but the top with every little bubble, bead, whatever you would like to call it, is on a line, which adds some evidence to my summary....for what its worth.

    IMO, inadequate dry times are a very common culprit in varnish problems, particularly with turpentine solvent based varnish, turpentine itself has the ability to REALLY soak into wood pores and stay wet for quite some time, thus wanting to off gas , which puts an exclamation point on the need for a proper ground coat that seals the wood with a dissimiliar base that will hopefully seal over the pores and not be resolventable based on being of a different base...

    beyond the dry times being pushed too close for recoating, the gelatin coat was most likely to thin and thus not that monolithic, which allows the following turp based varnish to fall into the pores...

    also, by applying the coat too soon to the first varnish coat, which may feel hand dry, it is only skinned and the second coat will resolvent the under coat and give the effect that is seen on the back, which is all the more reason to rely on your nose to tell you when something is dry rather than your hand.

    Dear jezzupe,

    thanks. Now I also do think that the probles is caused by not giving the varnish proper time to cure. It does not seem to be caused by the colourant as this would appear right after the first coat. 

    I'll run some tests as others advice me and I will see. Also I will kepp updating this topic if needed. 

    Thanky you all! 

    Dominik 

  3. 7 minutes ago, David Burgess said:

    Internet diagnosis can be really difficult. Next time I am in the Czech Republic (which I don't expect to be really soon), I'd be happy to get together with you, and we could probably nail this down in 15 minutes or less.

    Hahah, I see, that would be the easiest way to solve all these problems I have. Sorry for being so confusing - this is my first time varnishing and as you can see I am still not completely sure what I am doing! 

  4. 12 minutes ago, David Burgess said:

    I'm not seeing them as air-entrained blisters, since those tend to appear more whitish, due to the severe refractive index changes between air and varnish.

    Well, let's check that! If I understand that clearly, to ensure that the blisters are produced by gases they should be empty inside, filled with air, am I right?

  5. 16 hours ago, Mike_Danielson said:

    It looks like you goofed up and contaminated it with something like silicones.   That has already been pointed out to you.  Strip the instrument with alcohol.  

    Run tests on scrap pieces of wood to find out where the problem arises.

    Here is the secret that the old guys know--coat with a thin shellac coat between varnish coats to act as a contaminant seal.  If you never find the problem, this will still work.

    Mike D

    Isn't there any risk of combining oil varnish and spirit thinne shellac? 

  6. On 1/11/2019 at 7:33 PM, jezzupe said:

    Agree with David, if the "bumps" are not literally "wet" and are actually dry blisters, there is no mystery here at all, this is simply out gassing based on laying down too many coats with inadequate dry times in between....

    breifly, the gelitine ground, depending on the cut, most likely will not give a satisfactory seal, and or can, on a microscopic level not create a monolithic shell that will span the gaps in all the cell openings, this allows the succeeding solvent base coat to fill into these pores. 

    The problem then becomes relying on the "dry to the touch" declaration that it is "dry" and ready to be recoated. If the wood is then recoated with a second solvent base, as you describe, it will lay down, then start to dry, as it dries, it dries well over 99% of the surface, the "dry too touch surface" that it is adhering to, but what it is also doing is drying over pits and pores below the surface that act as "cups" that contain not completely dry varnish from the first solvent based coat.

    Once this second coat has skinned over the first, the solvents from the first coat will start to evaporate out of the pores and then these areas start to act like little hot air balloons , inflating the skinned over second coat , in the solvents natural attempt to evaporate. Once this happens you get what you have your work showing, dried bubbles,pocks or nibblets...

    IMO thats all nice fine and dandy, but you need to know what to do with it, imo I would not try to salvage this, I would whip out the turp rags and wipe it off, let it dry completely for several days, and then try again, giving more dry time in between coats...rely on your nose, not your hands for this, sniff the wood with your nose right on it, if you smell no solvent smell, then its good to go

    edit' also, if you do wipe it off, make sure you deal with and dispose of those rags properly so as to not start a spontaneous combustion fire, of you don't know what "proper" is, read up on it.

    From your describtion it seems that the problem could be the matter of not giving the varnish enough time to dry. The bumps really are sort of blisters or something. 

    Thank you for your advice. 

  7. Right - I have got this little update:

    I just varnished my viola. The steps were following: prepared surface, strong tea staining, gelatine applied. Then one coat of clear varnish. Once the varnish was dry I applied colourant on the back plate and put another coat of varnish. The result was nice, smooth and clear finish which I was satisfied with. Then I coloured the rest of the instrument and also gave it another coat over the colourant. This is still in the process of drying. But! Once I touched the already dry back plate (coloured and varnished) the sweating appeared! Absolutely confusing....

    Dominik

  8. On 1/9/2019 at 8:18 PM, Evan Smith said:

    What kind of oil is in the artist oil paint?

    Also it is best to not let the color coat completely dry before applying the next coat of varnish. It should be at the point of drying  that a bit of brushing will allow it to loosen up and start spreading around again. That way it will resolve and float in a layer in the varnish and not form a distinct layer and look like a layer of paint between coats of varnish. It can be tricky to do, it takes practice, timing is critical. Color it in several super thin coats instead of one thick one, thin color, thin varnish,, thin color  thin varnish, less is surely better. You can also add a bit of your varnish to the artist oil to increase compatibility, or put the artist paint into a jar of turp or whatever solvent you are using shake it up and let the pigment settle out, pour off the solvent then add the pigment to a small amount of your varnish to clean up the pigment and make it compatible. You can also add a bit of acetone or spike lavender or rosemary to your varnish to increase the wetting.

    Many cheap drug store versions have fillers in them, It is best to use high quality artists oils for color, use high quality,,,Old Holland, Schmincke, Daniel Smith,,,, no safflower oil.

    Dear Evan,

    thank you for you advices! These are my first instruments to varnish so...Long way to go I guess. 

    I have no idea what is the composition of paints I am using, it would be better idea to buy high quality ones I would say. Well, next time I will know. 

    Thanks

  9. On 1/9/2019 at 11:56 PM, FredN said:

    Hi Dominik, I've cooked  rosin with a saturated solution of calcium hydroxide wetted into crushed resin with umber pigment, cooked to dry, then added the oil for a final cook and never experienced  your problem. This makes me suspect the color coat or temperature of your cook. My cook is around 475oF for a few hours to where a drop on glass is no longer sticky when cool. Can you please describe the colored stuff and a little about cooking method.  thanks

    Hi Fred,

    to cook the varnish I melted 180 grams of colophony, into wich I added 10 grams of calcium hydroxide (lime) dissolved in about 30ml of water. Once the lime mixed with the colophony completely I poured in 180 mililitres of linseed oil and cooked the mixture for about one hour (the instructions told me to cook it for 30 minutes only but that was not sufficient). After one hour the varnish got darker thicker and had a decent string. I thought that one hour is not enough but since it was my first time cooking varnish I decided to stick to the instructions. After the varnish cooled a bit I added about 100ml of turpentine to thicken the varnish.

    Regarding the colourant - it is oil based artists' paint I have no clue what are its ingredients. It is not stated on the tube. That leads me to the point where I think that this might be the problem... 

  10. 50 minutes ago, HoGo said:

    I remember someone posting varnish experiment with undiclosed thinner that gave such bad beading with the second coat...  Year or so ago... Who was it? Don Noon or Mike Molnar?

    Yes that was Don's topic mentioned above. He had problems with thinner but it does not seem to by also my problem. 

  11. 36 minutes ago, Dave Slight said:

    Dominick, did you heat the oil before combining it with the colophony?

    Did you rub down the first coat with an abrasive before applying further coats?

    No I did not as this was my first time cooking varnish and the instructions did not say so.  I followed steps mentioned in this video: https://www.youtube.com/watch?v=gmHf5FHkh-c&t=18s .

    Yes I rubbed down the first coat on one of these instruments yet it was no help. 

     

     

  12. 8 hours ago, Dennis J said:

     The term sweating is relevant. Something is seeping through upper layers to the surface. There is a term used by artists using linseed oil based paints, and that is "Fat over thin." This means first coats on a canvas should be thin, plenty of solvent (gum turpentine) used to dilute the oil paint so that it dries or polymerises completely before thicker, oil-rich layers are applied.

    The culprit is either the final cooked oil varnish or the applications beforehand, or even perhaps a combination of both.

    It might be a good idea to check that your cooked varnish cures properly. If you applied a thick layer of this varnish to a piece of wood without any other underlying coats and allowed it to cure completely you should be able to detect any oil seeping to the surface. If it passes the test you will then know that the problem is probably with what lies beneath.

    I know that luthiers use all sorts of grounds and sealers under varnish for various purposes, but I'm beginning to wonder If they are more trouble than they are worth.

    I tend to think that a coloured varnish over bare wood may be the best way to go.

     

    I surely should do some testing on plain wood or to combine my techniques on some scrap samples to figure out what is wrong. I will definitely keep updating this topic. 

  13. 9 hours ago, Don Noon said:

    It looks similar to a problem I had with the varnish beading up terribly instead of wetting the surface underneath.  There was a thread about it here.

    In my case, it was due to the thinner that I used in the varnish.  I re-cooked the varnish to boil out the solvent, added a different thinner, and the problem was gone.

    In any case, it's a wetting problem... could be surface contamination, as David suggested.

    Thanks Don!

    I also thought it could be something with the thinner but I do not understand why it wouldn't occur when the first one or two coats are applied. Maybe the third + coat somehow reacts with the first two? 

  14. 32 minutes ago, David Burgess said:

    Dominik, it's still not clear what the pictures are showing. Is this a varnish which was applied, then formed this pattern and dried that way, or is it a liquid which has developed on the surface after the coating has dried?

    The varnish showed in the pictutres is in the process of drying. The coats applied before were all right. Once I applied another coat the problem occured as soon as the varnish touched the instrument.  

  15. 10 hours ago, FredN said:

    since you say it is an oil colorant I assume it is a metal based suspended  in the oil, so that is not a problem. Lime is used to reduce the acidity (ca 5% cooked in) to make the final varnish  more durable. Cooked in at around 400oF. Can you describe how you make your varnish, is the lime added directly to rosin, not as a mixture. Thanks

    Dear FredN,

    to cook the varnish I melt the colophony first. After all the colophony is melted I dissolve a bit of the lime in the water and slowly add it into the colophony. Once all the lime is mixed with it I add linseed oil and boil this mixture until I have decent string. After that I let the varnish to cool a bit and then I add a bit of turpentine to thin the varnish a little bit. 

  16. 4 minutes ago, FredN said:

    the gelatin is giving you a condition of "surface  tension" is greater than "surface attraction", ie, that there is no adhesion of the proceeding oil coat to the gelatin coat, so it balls up. My guess.

    I do not think so. The violin with the crack has no gelatine sealer and the problem still appears. 

  17. 1 hour ago, David Burgess said:

    Is this varnish which is beaded up on the surface? If so, it looks like the surface has been contaminated with some kind of oil or silicone. What exactly is the "lime" you mention in your list ingredients?

    The lime I am refering to is calcium hydroxide to bring down the melting point of the colophonny. 

  18. 49 minutes ago, James M. Jones said:

    Cooked varnish can vary widely with temp and time and recipes, decisions on when to quit heat , .... What does it do without the color layer, have you tested that? I,ve had similar experience happen both from over thinning with solvent and applied to thick, as well as miss matched varnish, ....I suspect. 

    Thanks for the answer!

    Yes, I have tested that. It dries after some two weeks and then the varnish is perfectly clear. 

  19. 3 minutes ago, Dave Slight said:

    Given that the belly appears to have dark cracks on the bass side, was this instrument stripped first, and if so, what did you use?

    When you were varnishing this, just how dry was the ground before proceeding?

    How long did the varnish coats take to dry, how many coats did you use?

    What did you use to dry the varnish? nothing, uv or driers?

    Thanks for the answer!

    There are actually two violins in the photographs. The one with the crack was stripped years ago. I simply scraped down the old varnish (for training purposes) with scraper, then applied the colourant and then the oil varnish. First coat was great, varnish turned out to be very clear. After two or three weeks I applied second coat and then the sweating happened. To dry the varnish I used just the sunlight. 

    The second violin, the one without the crack and the one made by me, was sealed using gelatine, then I applied thin layer of oil varnish, and then another coat of varnish mixed with artists' paint. Sweating happened.

    I have got another instrument - viola - that was also sealed, also had one thin layer of varnish, also had colourant and also had another coat of oil varnish and nothing happened. I am confused!  

  20. Dear with_joerg,

    as an amateur maker I was in the same position as you are and I have developed this rule - do it to liking. Unless you are copying an instrument, do what suits you, wheter it is 10mm or 15mm in the narrowest area, simply be somewhere close. This way you will learn to carve and the future scrolls are going to be better and better. 

    Best wishes!

    Dominik 

  21. Dear Maestronetters,

    I have absolutely no idea whether "sweating" is relevant verb thus I am including some photographs. 

    I have got this problem with my oil varnish - after it is applied it creates sort of tears, drops, lakes. My varnishing process is following - I prepare the surface, apply gelatine, than thin ground coat of my oil varnish (colophony, turpentine, linseed oil, lime), after it is dry I apply thin coat of artists' oil paint (colourant) and after the paint is dry I apply another coats of my cooked varnish. And then the problem begins. 

    What could be wrong? I understand that some ingredient is drying faster than the other but why would it happen when the artists' paint is completely dry (even for several years)? 

    Thank you in advance! 

    Dominik

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