sanding beyond 220

Re: sanding beyond 220

john lucas

>Tom I am a turner and have always wondered about sanding to finer grits. I usually sand to 400 unless it's something like ebony and I'm going to use an oil finish. I usually finish with lacquer so I wondered how far you need to sand with a thick bodied finish like lacquer. I took 4 board (I would have to dig them out to tell you what species for sure but I think it was cherry, walnut, maple and oak)

I sanded them in sections from 220 up through 12oo and then finished some with and oil based finish(don't remember which one without looking at my samples) and finished the others with several coats of laquer. Then I buffed them all with the Beal buffing system.

When I passed the samples around our club no one could tell a difference in anything beyond 600 grit and on the lacquer samples 400 grit. I really expected more brilliance in the figure or something but to my eye with these particlular finishes, sanding beyond 600 was a waste.

Now this wasn't a turning with highly figured wood and grain running every different direction. The maple was fiddle back.

In short it was an interesting test but requires more testing to be really useful. I didn't have planed and non sanded board. I only used 2 finishes and of course I mentioned that it was only flat wood.

For me I will continue to sand to 400 and rarely higher as long as I'm using lacquer as my finish.

Because of OCD

Clint Searl, at the base of Haycock Mtn

>

um, Optical, uh, Circumference...

Tom Sontag - St. Louis

>Optical Circular Delusion?

No, no, it must be Opticular Circasian Development. Nope.

Google says its Obsessive Compulsive Disorder! So, I take it your not a believer huh?

because they can

bill tindal, E.TN

>You are correct if there is little finish above the surface of the wood then sanding finer matters. But the ease of doing it on a lathe encourages over sanding.

220 is the practical limit for a finish that has some build and that would be varnish, lacquer, shellac, for example. The grainy wood I don't sand beyond 180- eg oak.

Re: sanding beyond 220

Ellis Walentine

>John, I suspect that by buffing all your samples, you may have masked the results of your test. The buffing step is a great equalizer and tends to hide the flaws of the larger grits of sandpaper.

On flat work, where the Beall buffing system isn't an option, you need to rely on the combination of surface quality and finish depth to produce the desired appearance. I agree with Bill that 220 is about far enough to sand if you're planning on applying a film finish. I suspect that if you really examined the finished surfaces at higher magnification, you would be able to see some difference in the clarity of wood sanded to finer grits, but for all intents and purposes, the extra sanding is lost on the viewer.

On very hard, dense woods and exotics I often go farther, say to 320 or 400 -- rarely 600, particularly when using a close-to-the-wood finish like a Danish oil -- because often these woods have a cell structure that seems to have more depth and shine when polished to a higher grit. The finish just provides a window into this depth, sorta like a glass-bottom boat.

Ellis

Re: sanding beyond 220

Barry Irby

>Tom, I am having more and more trouble teling when I am finished sanding. (Age induced eye failure?) I sand until I think I'm finished and then take the piece out into the sun. Then I sand some more. IT'S the SUN!!! Don't let it see your work! It burns scratches into it instantly!

I think turners sand to extremes because they are almost always sanding across grain. Aslo many of there shapes are very distint and geometric, sort of inviting close examination and making any imperfection stand out.

On flat work we have the option of usually sanding with the grain which tends to hide some of the fine scratches. Somewhere along the way, I thought I was given to understand that part of what sanding did was to remove The bits and pieces of torn wood cells from the surface, leaving mostly complete closed cells. Don't actually know if that's true, but it might have some effect.

I usually sand flat work to 220 and give it a light pass with 320 on the ROS. Then let the sun see it.

FWW just did a test

Joe Piotrowski - Chicago Burb's

>like most it's subjective but the author found you don't need to sand too much.

he says that less than 220 on most woods. he used three finishes on three woods. basically open grain woods like oak or figured woods like tiger maple did not need to go over 220.

only blotchy wood was better at 400.

the article is decent but not complete enough for me. It seams open to a discussion of the effects it has on a topcoat you use.

this finishing part drives me nuts. it seams that if you find a process with results you like, it the right one.

personally, I hate sanding so if 150 will do for oak, I'm ok with that!

Re: sanding beyond 220

Lee Ohmart

>I agree that on oak, 220 is good enough. When I recently worked with some ash, when I got up to 220, I noticed a wavy figure appear. Earlier reading about chatoyance had included the advice to sand to a very fine grit or use a scraper to enhance this property so I kept going finer in grits until I got to 600 (the finest I had at that time). At each stage the chatoyance became more noticable. Given this experience, I will continue to sand up to this point on dense wood where there is a possibility of capturing this beautiful look.

Re: Some Tests

Howard Acheson

>Sanding wood--hard or soft--beyond 220 does little more than burnish the wood making staining difficult. This is particularly true if you are using a pigment stain which sits on the surface and relies on "nooks and crannies" to impart color. Softer more porous woods can be sanded to to 220 but harder less absorbent woods may stain best if only sanded to 150.

A number of years ago a large cabinet/custom furniture shop I was involved with did series of adhesion tests with various finishes and sealers. As part of this test we explored adhesion based on sanding grit. We found about the same adhesion up to 180 - 220. Beyond 220 adhesion dropped off due to burnishing of the underlying wood particularly when non-linear machine sanders were used. This was tested on birch panels. We also found that the resulting smoothness of the first coat of finish was not materially affected by the smoothnes of the underlying wood for sandpaper grits between 150 - 220.. The smoothest surface substrate for final finishes was obtained by sanding lightly after the first coat of finish was applied and dry. Which makes the case for a thinned first coat of finish.

So our conclusion was that sanding beyond 180-220 was not necessary and could be actually detrimental.

But, most important was that there was a big appearance affect if the surface was not HAND sanded in the direction of the grain using the highest grit used on the sanding machine. A flat pad sander produced a much flatter surface than a ROS. However, both required final hand sanding with the grain for optimum appearence. If not hand sanded, swirl scratches could show. Final hand sanding using a sanding pad in the direction of the grain is a must.

To carry it one step further, sanding at 320-400 grit after the first coat and subsequent coats was the optimum. No improved appearence was noticed by between coat sanding beyond 400 for varnish. 400 was the sweet spot for thinner finishes. Between coat sanding was always done by hand whether for flattening or for adhesion.

I think you will find similar thoughts in the popular finishing books but YMMV.

A final point. ANY finish causes little shards of wood to swell, raise up and harden. It's these shards that cause the rough feel after only one coat of finish. Sanding after the first coat has dried removes these shards and future coats dry smoother.

Re: sanding beyond 220

Robby Wright in San Marcos, CA

>One thing I haven't seen mentioned was the feel of the finished item. I was given a Japanese lantern a few years ago and the feel of the finish was incredible. I don't know how it was done, but it was silky smooth and a lot of fun to handle.

Robby Wright