Finishing with a scraper as opposed to sandpaper...

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Finishing with a scraper as opposed to sandpaper...

Postby Zach Schryer-Lefebvre » Sun Feb 12, 2012 9:20 pm

I had a question that is based on violin luthier beliefs.. Does it really make a difference to finish surfaces with a scraper as opposed to sandpaper (acoustically speaking).
Sandpaper tears the grain and scrapers shave it, so should I avoid using sandpaper at all if it's possible?
Thanks,
Zach
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Re: Finishing with a scraper as opposed to sandpaper...

Postby John Hamlett » Mon Feb 13, 2012 12:09 am

Sandpaper is basically a whole bunch of little scrapers glued to a piece of paper. The cutting action with sandpaper, though locally somewhat less controlled than a metal scraper, is the same type of cutting action; scraping. If anyone claims to be able to hear a difference they'll have to show me double blind test results to convince me. I believe we're in the realm of differing traditions here, and no more.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Michael Lewis » Mon Feb 13, 2012 2:36 am

If you are going to finish with scrapers you had better keep them sharp. Scrapers also tear wood grain if not kept very sharp.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Øyvind Taraldsen » Mon Feb 13, 2012 7:05 am

Acoustically there is no difference assuming you remove about the same amount of material.

Edit: I have seen very few violinmakers claim that scraping makes a difference to the sound, it does however give a slightly different look, depending on how you use it. When scraping a spruce top with a somewhat dull scraper, you can get a sort of reeded surface texture due to the alternating hard and soft grainlines of spruce, and when scraping flamed maple you can get a sort of washboard effect because of the way the scraper follows the flame. These visual effects are sometimes dessireable on violins, because they are found on the italian instruments.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Alan Carruth » Mon Feb 13, 2012 4:09 pm

Even when scraping soft wood with a sharp scraper you'll get that 'reeded' look. The scraper unavoidably compresses the softer earlywood and cuts the hard latewood lines in between. Later, the earlywood swells back up, and you get that 'corduroy' appearance. Since this is what Strad did, it's a look that's prized by the violin community, and, of course, it _must_ sound great because that's what Strad did, right? ;)

Guitar players are used to seeing sanded surfaces, which will either be perfectly level, if you did it right, or have the softer parts slightly below the level if you didn't. A scraped top on a guitar is a terrible flaw, from their perspective, and, since it looks so bad, it must sound awful, right? ;)

It makes no sense, but that's the way it is.

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Re: Finishing with a scraper as opposed to sandpaper...

Postby Barry Guest » Wed Feb 15, 2012 7:34 am

So that's the way it is? I say hogwash!!!! The acoustic properties of wood are not dependent whether a surface is sanded or scraped. Some idiots in the violin world, a prominent Texan included, pretend that the wood they use is somehow different, and requires different treatment from the wood the makers of other stringed instruments use, even though it may come from the same tree!

I for one, cannot believe the crap that has been written ad nauseum about the "secrets of Stradivari" et al. Can someone close to the top of the tree (no pun intended) come out and say that Stradivari and his peers had NO secrets....That they were part of an age that practiced perfectionism and were included in an evolution of deign and form that manifested itself in their time. .... something like Edison and the light bulb.

Anyway, Uncle Tony used sharkskin!!!
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Charlie Schultz » Wed Feb 15, 2012 8:15 am

Speaking of Strads, an interesting article here: http://www.npr.org/blogs/deceptivecaden ... -the-strad
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Steve Senseney » Wed Feb 15, 2012 12:05 pm

Nice link!!
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Barry Guest » Wed Feb 15, 2012 5:07 pm

Well there you go Charlie. More proof that the secrets don't exist. But somehow, that research will be discredited and the "protectors of the myth" will come through it unscathed. You see, it's all about greed rather than excellence, and we plebs swallow it every time because we love a good mystery!!

Can't wait for the revolution!!!
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Bill Hicklin » Wed Feb 15, 2012 6:53 pm

I suspect that there's a lot of cork-sniffery in lutherie- "Our Superaxe guitars' tuners are attached with titanium-alloy screws for improved tone!"
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Re: Finishing with a scraper as opposed to sandpaper...

Postby John Hamlett » Wed Feb 15, 2012 9:22 pm

Charlie Schultz wrote:Speaking of Strads, an interesting article here: http://www.npr.org/blogs/deceptivecaden ... -the-strad


I guess those 'new' violins were scraped, not sanded, or they surely would have heard the difference.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Clay Schaeffer » Thu Feb 16, 2012 12:09 pm

And perhaps their varnish was shaken, not stirred.<g>
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Bill Hicklin » Thu Feb 16, 2012 12:44 pm

"it's all about greed rather than excellence"

Not necessarily- a lot of builders truly believe in 'magic', especially if it's hallowed by tradition.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Alan Carruth » Thu Feb 16, 2012 1:19 pm

A big problem is that we simply don't know what makes a great violin (or guitar) great. In the absence of real understanding, tradition is the only guide, and makers are afraid to change anything at all. The designs we have are pretty highly optimized, after all, and this means that the difference between the best and the worst examples is likely to be in the details. Strad seems to have understood more about how these things work than we do ( the utility of a living tradition), at least at a gut level, and to have made changes all the time to achieve a more or less consistent result. Pehaps that's a big part of his fame; it's not that his best was better than anybody else's, but maybe he simply was more consistent in producing at a high level. We can see the changes, but have no idea why he made them (assuming there _was_ a 'why'), so we just copy as well as we can, and hope to hit it right.

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Re: Finishing with a scraper as opposed to sandpaper...

Postby Bill Hicklin » Thu Feb 16, 2012 3:43 pm

I would say also that there's an element of conditioning as well- we say Strads sound the 'best' because 'best' has become defined as 'what a Stradivarius sounds like.' This wasn't always the case: there's a letter from Leopold Mozart to his son advising him to buy an Amati or Stainer but *not* a Strad, which L considered loud but "coarse." It seems that Stradivaris didn't gain their reputation as superfiddles until after 1800, perhaps because that volume was by then desirable against the growing orchestra of the day.

Something similar applies with "good" amplifier tone, a tone which arose not by design but rather out of Leo Fenders' adapting fairly crude RCA handbook circuits, and blues players cranking them into hard clipping to be heard in noisy bars. Therefore we expect a "good" amplifier, whatever its guts, to sound like an overdriven tweed box of tubes.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Andrew Porter » Thu Feb 16, 2012 4:19 pm

Returning to scrapers, any recommendation on types and source. My big box store thinks they're only for removing paint.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Ron Belanger » Thu Feb 16, 2012 6:00 pm

Lee Valley and Woodcraft have good selections of cabinet scrapers or you can make your own out of any good steel such as old handsaws or bandsaw blades. For smaller scrapers I use single edge razor blades and the blue steel razor knife blades (from Canadian tire here in Canada)
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Re: Finishing with a scraper as opposed to sandpaper...

Postby John Hamlett » Thu Feb 16, 2012 7:21 pm

I've made scrapers from saw blades with varying degrees of success, saws are not created equal.
I use different scrapers for different purposes. For rough work, and for maple and other hardwoods, I use a standard "cabinet scarper", actually a hand scraper, sharpened to 90 degrees at the edge with a burnished hook on each side. I burnish more or less hook depending on the situation. For spruce and for finer work, I use thinner, smaller scrapers sharpened to about a 45 degree angle with only a light rolled burr, or none at all.
The hand scrapers I have are German (two cherries, perhaps.... not sure anymore) and Scandinavian (Sandvic). Both are OK, I like the German one better, my favorite was an old Diston, made in USA, but you can't get those anymore.
The "violin" scrapers I have came from International Violin.
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Re: Finishing with a scraper as opposed to sandpaper...

Postby Alan Carruth » Mon Feb 20, 2012 4:51 pm

The best design for a scraper that I've run across is one I picked up from Carleen Hutchins, and she from Saconni. It's a piece of fully hard tool steel, something like .1" thick or so, and ground to any shape you choose. In use, you lap the faces flat, and then hollow grind the edge perpendicular to the faces, in the same way that ice skates are sharpened. You don't turn a burr (you couldn't anyway: the tool's as hard as your burnisher); the burr from the grinding is the cutting edge.

In use, the scraper is held as close to upright as possible while still getting a cut. This 'backs up' the edge best, so that it lasts a long time, and produces the best cut. Because it's made of hard steel, this sort of scraper can hold an edge for a long time. It also does not get nearly as hot as a thin spring steel scraper. You don't 'spring' it in use (if you can, my hat's off to you...), so it can be used with either hand, in either direction. This sort of scraper in much easier to sharpen than the traditional one. When using it for scraping arches, or on figured wood, I find it much easier to get a good surface with no chattering with the heavy scraper, due to the added mass.

Up until fairly recently the only way I could get one was to make it. This proved to be a drag: all of my students wanted one as soon as they tried mine, and we ended up making them during classes. Then I got a student who's brother-in-law runs a machine shop. They're now getting things going with Stew-Mac, and the scrapers should show up in the catalog pretty soon. I report with some embarassement that they're talking about calling them the 'Al Carruth Ultimate Scraper' or something like that. I hasten to point out that the _only_ benefit I'm getting from this is that I no longer have to dunk pieces of red-hot steel into cans of oil in the shop; which is benefit enough for me! Anyway, there's nothing that says you can't make one for yourself, and I think that, once you try it, you'll like it.

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Re: Finishing with a scraper as opposed to sandpaper...

Postby Bob Menzel » Tue Feb 21, 2012 3:05 pm

That sounds pretty cool Al (cudos?), but how does one hollow grind it? As an alternative I guess I could take the blades off my CCM's and have them sharpened at the rink and use them as scrapers. (kind of seriously)
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