Getting a smooth surface for varnishing

[Kallie]

Hi,

 

How do you get a perfectly smooth surface for varnishing when making a violin? It seems there is always a few tool marks left over when I try. Any advice on this?

 

Thank you.

[Violadamore]

Do what GDG did and ignore it.  People like me will call it "character" and be less likely to confuse it with Chinese when looking at it  .

[duane88]

practice, practice, practice...a sharp scraper, more practice...resist the urge to attempt to smooth and flatten with sand paper. it won't work.

[not telling]

Shaving grass is lovely too. Also...what VdA said.

[Stephen Faulk]

*caution: file nerd talk* 

 

I probably should not say this, but on some convex surfaces I use flat metal files for some smoothing. It has limitations because you can't really fine file concaves, but many things that can be done with knives also are good with fine files.

 

On the cello back I built I used a technique called 'draw filing' to do some smoothing. You hold one end of the file in each hand with thumb and finger tips and draw it over the surface towards you. The file teeth are then at a angle to the direction of the draw over the work and they cut like a line of tiny scrapers. It has limitations, but it is a good technique to know for many applications. If you see tooth marks or chatter marks turn the file like a drivers wheel until it stops. Practice on scrap wood to learn. 

 

Files also have, usually, a 'back' and 'belly' sight down the file and see which way it warps. Half the files you see in the store are warped, a  few are perfectly flat. Keep that belly and back side idea in mind when setting the file down on things you are working on. A file can have a lot of belly and be more aggressive in the middle of the blade, then flip the file over and the ends become more aggressive. Check it out on big files. Usually larger Bastard or Mill pattern files have back and belly sides. A 10" Rough Mill pattern file with a pronounced  belly side means business! 

 

 

 

Other than that, keep your scrapers sharp, wear gloves and go slow.  

[JohnCockburn]

Hi, as well as getting your scrapers sharp, it's important to use light wisely to reveal the lumps and bumps that you're trying to eradicate.

A low angle single point light source in an otherwise darkened room is very effective, but I always find it useful to combine this with looking under diffuse daylight. One method always seems to reveal bumps that the other doesn't. To me, anyway.

[Kallie]

Thank you for the replies so far. I have been using scrapers, but even they seem to be leaving scratch marks. Would that mean it is maybe not sharp enough?

[Kev Chanot]

Thank you for the replies so far. I have been using scrapers, but even they seem to be leaving scratch marks. Would that mean it is maybe not sharp enough?

The edges of your scrapers need to be smooth before you put a burr on them.This should eliminate any scratching.

[Davide Sora]

Thank you for the replies so far. I have been using scrapers, but even they seem to be leaving scratch marks. Would that mean it is maybe not sharp enough?

 

Mostly yes, but even that probably you are using too much pressure.

To obtain a surface as smooth as possible with the scraper (if this is your goal) is necessary to make the final steps being very very light with the scraper, the smoother surface is obtained by pushing the scraper instead of pulling (90° cutting angle required).

Probably GdG  never used this technique (too many tool marks on the finished surface) but maybe Strad sometimes........surely not on the Messia top, otherwise there would be less "corduroy" effect.

 

Davide

[Kallie]

Thank you for the replies. Will try the advice given and hopefully it will fix the problem.

[FredN]

As someone mentioned scrapers shouldn't leave a scratch unless there is a nick in the blade or the corners are a problem. A good step before varnishing is to use pumice with small various shaped wood blocks that sort of conform  to the area smoothing (eg,dowels for the gutter area). Don't go parallel to the grain or you'll remove the soft summer wood from the top. Compare what you are doing with dry pumice and wood blocks, I think you'll find an improvement.  fred

[Smith]

.

[Kallie]

There used to be a self taught violin maker here named Dale Stevens that did amazingly clean varnish jobs, and he told me how he prepared his instrument for varnish. He would sand the surface of the instrument down three times with increasingly finer sandpaper, in between each sanding he would wet the wood to raise the grain. Then he would take an extremely sharp scraper and scrape the wood gently all over just to get rid of the sandpaper dust and bring back the sheen to the wood. I don't know if he did that to the top or not, but the maple I'm sure. Its also really important if you want to hide any scraper marks to put down a couple of coats of clear or golden varnish first, and gently rub it down a bit to smooth it out. If you go on with a lot of color early on, when you rub the instrument down then all those scraper and sanding marks will stick out like a sore thumb. So part of the trick to hiding the marks which you didn't see is in the initial coats of varnish.

 

Thank you very much for the advice.

[Michael_Molnar]

The edges of your scrapers need to be smooth before you put a burr on them.This should eliminate any scratching.

Very true!

[Bill Yacey]

Also keep in mind, the larger the burr, the coarser the cut. For really fine finishing use very light pressure on the burnishing tool when turning the burr.

[skiingfiddler]

Do what GDG did and ignore it.  People like me will call it "character" and be less likely to confuse it with Chinese when looking at it  .

That's definitely a possibility.

 

Kallie,

 

I saw a fiddle in the late 1990s from an up-and-coming, professionally trained, professional maker who deliberately scalloped the violin top in very regular, shallow rows, creating a kind of subtle fish scale effect.  It was beautiful.  I also believe that some contemporary makers will scrape the back in such a way as to create a bumpy surface, where the bumps correlate with the flames.  This is in imitation of what you see on some very fine old Cremonas, the Kreisler del Gesu in the Library of Congress, for example.

 

So, there are alternatives to getting a perfectly smooth surface.

 

Steven Csik

[David Burgess]

If you want a really smooth surface, sharpen the scraper edge smoothly (no pits or bumps) to the point where it shaves hair before turning the edge over. Or sand the chit out of everything, using progressively finer grades.

 

I don't consider that kind of smoothness to be desirable though. What kind of look are you going for? Can you post some pictures of things you like?

 

Keep in mind that we're not out to make modern geeeetars or bowling alleys here.

[Urban Luthier]

what about simply scraping with a sharp scraper and burnishing with a rough piece of linen afterwards? 

[Kallie]

That's definitely a possibility.

 

Kallie,

 

I saw a fiddle in the late 1990s from an up-and-coming, professionally trained, professional maker who deliberately scalloped the violin top in very regular, shallow rows, creating a kind of subtle fish scale effect.  It was beautiful.  I also believe that some contemporary makers will scrape the back in such a way as to create a bumpy surface, where the bumps correlate with the flames.  This is in imitation of what you see on some very fine old Cremonas, the Kreisler del Gesu in the Library of Congress, for example.

 

So, there are alternatives to getting a perfectly smooth surface.

 

Steven Csik

 

Thank you, Steven.

 

 

If you want a really smooth surface, sharpen the scraper edge smoothly (no pits or bumps) to the point where it shaves hair before turning the edge over. Or sand the chit out of everything, using progressively finer grades.

 

I don't consider that kind of smoothness to be desirable though. What kind of look are you going for? Can you post some pictures of things you like?

 

Keep in mind that we're not out to make modern geeeetars or bowling alleys here.

 

Thank you David. My objective isn't necessarily to get the surface absolutely perfectly smooth. Just up to the point that there wont be scratch lines visible underneath the varnish. My main reason for starting the topic was to learn how to eliminate the scratch marks caused by the scrapers. The last thing I want is visible scratches underneath the varnish - that which causes it to look like someone sanded it with heavy grid sandpaper

[David Beard]

It might be interesting also to note some older art and woodworking practices, even if they aren't currently discussed much for instrument making.

 

Besides scraping, and rubbing with 'rushes' or horsetail, or sharkskin, there are some other smoothing abrasives that behave differently than either sandpaper, files, or loose grit.  Various natural materials present abrasion in an erodable strata.  These would include various grades of actual pumice stone, rather than powdered pumice, and also include materials like cuttlefish bone.   Such 'erodable strata' abrasives strike a middle ground between the action of a file which follows your hand instead of the wood, and things like sandpaper that tend to follow the wood too much leading to lumpiness.  Erodable abrasives strike a sort of calculated average between the carved shape in the wood and the direction of your hand's motion. 

 

Also, after scraping or abrasive smoothing, many practices (perhaps virtual all traditional work????) included sizing of some kind immediately prior to applying varnish or other finishing materials.  Sizing can mean many things, from garlic juice, to hide glue, to very thin varnishes, to egg white or starches, etc.  Sizings generally help create a more unified and even texture and tooth, lending evenness and predicatablity in applying the next coating. 

 

Whatever the kind, sizes should be thick enough to effect and unify the texture of the material, but thin enough to not 'cover' at all.  They should not present any shininess over the material once dry.

[not telling]

Garlic juice?

Do tell. Have you used this?

[Carl Stross]

Garlic juice?

Do tell. Have you used this?

 

It's excellent. Myself can't use it though : I'm allergic....

[Kallie]

Garlic juice?

Do tell. Have you used this?

 

Atleast it will keep the vampires away.

[not telling]

Seems like a lot of effort. I like plant-origin sizing options though.

[David Burgess]

It's also great for preventing unplanned pregnancy. Eat a bunch, and then rub the rest all over your body, particularly the nether regions. Cat poo works almost as well.