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Scraping vs sanding .weight difference on finished product?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=32838		 Page 1 of 1
Author:  wolfsearcher [ Tue Jul 12, 2011 12:58 am ]
Post subject:  Scraping vs sanding .weight difference on finished product?
Hello everyone
Just pondering a bit much proberly ,but i might as well ask
Ive never heard anyone mention if their was any weight difference in the final product ,
on the subject of planing vs sanding
Could say ...a sanded top be filled with dust more , than a scraped finish
would it have possibly more sealer absorbed ?

,and ive heard that a plane ''crushes'' the pores
so could that mean you have less sealer to apply ?
thanks again [:Y:]
tomas
Author:  Link Van Cleave [ Tue Jul 12, 2011 2:31 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
Tomas,
You have me confused.
Let see if I can sort this out.
Your title says.... "Scraping vs sanding"

Then you say......."on the subject of planing vs sanding"

Then you say........"a sanded top be filled with dust more , than a scraped finish"

And finally you say..... ,"and ive heard that a plane ''crushes'' the pores" wow7-eyes idunno [uncle]

I will tackle the last first. That is the polar opposite of what happens. A plane leaves open pores.

As for the weight difference, for any practical purposes, none, nada, nothing. Most all the top woods don't have very deep pores to hold any dust anyway.

As to comparing a scraped finish with a raw sanded top idunno

As to planing vs. sanding, a hand planed surface tends to have open pores and a sanded surface crushed or crumbled pores.
As to scraping vs. sanding, they are somewhat comparable at least under high magnification.
Check out Bruce Hoadlys "Understanding Wood" for high magnification photos of surface comparisons between scraping, sanding and planing.

L.
Author:  bluescreek [ Tue Jul 12, 2011 6:41 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
the difference would be subject to the techniques of the user. I think you are over thinking this a bit.
Author:  Laurent Brondel [ Tue Jul 12, 2011 7:40 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
I can't see what difference there would be. Dust in the pores is only superficial and blown out easily. It is very difficult to get a perfect scraped surface that does not show scratches under finish. No difference in the application of finish. The only difference I would see is in staining, the coarser the surface, the more colour it absorbs, the more uneven colour is between end and side grain, and the darker it gets.
Author:  David Newton [ Tue Jul 12, 2011 8:10 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
Maybe the OP is just looking for comparisons between scraping and sanding in a general sense.

A scraped surface can be smoother than a sanded one, initially, but once finish sanded and under finish, the difference disappears, for all practical purposes.
It can be difficult to achieve as "flat and smooth to the eye" surface with a scraper, over a broad surface like a top or back, compared to a sanding block.

But, in the ideal world of one's own making, wouldn't it be lovely to build guitars with a scraped finish, and a workman-like finish.
Author:  bluescreek [ Tue Jul 12, 2011 8:14 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
A note of caution . Too smooth of a surface and you can have finish adhesive problems . I don't go past 220 grit . That gives the finish some tooth.
Author:  wolfsearcher [ Tue Jul 12, 2011 8:37 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
Thanks for the replys guys
Sorry i could have mentioned in other factors
(like finish results)
mentioning hand planing b + s sets, and then the final binding scraping

and not doing the ''before you go to sleep post" :roll:
I just thought you might be able to get proof with a weight question .

Link Van Cleave wrote:
I will tackle the last first. That is the polar opposite of what happens. A plane leaves open pores.
L.

I thought i heard the opposite recently on some youtube vid
i think ill stick to this site for my education
and will buy understanding wood before i get some fancy wood

[quote="Laurent Brondel"] The only difference I would see is in staining, the coarser the surface, the more colour it absorbs, the more uneven colour is between end and side grain, and the darker it gets.

Thanks on the comment i was trying to get some info regarding this aswell but failed laughing6-hehe
thanks again ,i wont post when im sleepy anymore
tomas
Author:  npalen [ Tue Jul 12, 2011 3:14 pm ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
bluescreek wrote:
A note of caution . Too smooth of a surface and you can have finish adhesive problems . I don't go past 220 grit . That gives the finish some tooth.

John, I agree with you on this but there are some OLFers that will vehemently disagree.
Nelson
Author:  bluescreek [ Tue Jul 12, 2011 3:27 pm ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
I look at finishing as prep. I need the wood to be shinier than the finish . I agree some finishes will adhere but I use Nitro and have seen first hand the problem of adhesion issues. Remember todays finishes are not what they were 10 years ago . Still we agree to disagree . Looking forward to Woodstock and hope to see some of you guys there.-
Author:  jfmckenna [ Wed Jul 13, 2011 10:04 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
A dull scraper may crush the fibers but a properly sharpened one will slice them and leave them open. The last guitar I built I did with no sand paper at all. The Spruce top was very difficult and as a result it has some crushed areas where the annular grains stick up relative to the softer material between them but it still took the finish as usual. I just chalk it up to looking cool :)
Author:  John Arnold [ Wed Jul 13, 2011 9:53 pm ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
Quote:
Too smooth of a surface and you can have finish adhesive problems . I don't go past 220 grit . That gives the finish some tooth.

In my experience, it is incompatibility from oily woods that is the main problem with adhesion, rather than the surface texture.
With that in mind, my usual standard is to sand just fine enough so you don't see scratches under the finish. In most cases, 220 grit accomplishes that.
Whether you sand, scrape, or plane, there is some compression of the wood fibers. This is best dealt with before applying finish by raising the grain and leveling it with very fine sandpaper or steel wool.
I learned this after a hard lesson. I had some of my spruce tops thickness sanded with 150 grit at a local furniture factory. They ran the joined tops through at an angle of about 15 degrees. Even though I sanded the surface smooth with 220, the angled scratches still showed when the finish was applied. That is because the wood fibers were actually dented by the power sanding, creating 'virtual' scratches. It is the same effect as curly or quilted wood. The distorted fibers create the illusion of an uneven surface.
Author:  Laurent Brondel [ Thu Jul 14, 2011 7:18 am ]
Post subject:  Re: Scraping vs sanding .weight difference on finished product?
Nice to see you post here more often John. I agree about adhesion having more to do with oils and/or contaminated surfaces. I routinely sand my necks up to 400grit when I stain them. It gives me a more uniform colour, especially on the end grain of the heel and handstops. Also it is very difficult to eliminate all sanding scratches there as the grain changes direction, it is all the more obvious with dark stains. A good sealer, like shellac or thinned varnish, will adhere without issue on surfaces sanded even finer than 400.
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