Sanding to perfection question? Need Help

Before you finish ...

Michael Farinella

always shine a bright light perpendicular to the surface.

Re: Sanding to perfection question?  Need Help

Dick Coers

Try magnification. Head band magnifiers even have LEDs on them now. My first step after super rough sanding like that is a French curve card scraper.

Raking light

Jack Guzman from Maine

When I am sculpting a windsor chair seat,and nearing the end, I will turn off the over head lights. This makes it easier to see defects in the surface. The light comes from windows but any raking light should do the same if you are in a room with no sunlight.

Scrapers

I'm impressed, Thanks to all of you & Q No 2

Barry Irby

Thank you all. Good ideas to try. Not sure about the lighted magnifiers....seems like I would be admitting a problem....

I will work on the lighting and flashlight Ideas.

Does anyone have any experience with fuming? Specifically repairing a fumed surface? I wonder if you could sand out a spot and put it back in the fumes? Would it come out even or would the spot always show? And to compound it even further, what about after the urethane finish has been applied?

I am thinking you would have to sand all the way back to raw wood on the entire surface.

Re: I'm impressed, Thanks to all of you & Q No 2

Jesse Cloud

Hey Barry,

Don't dismiss the magnifiers too quickly. I use them for post sanding inspections and they help a lot, even though I have the old school magnifier visor without light. The slanted light is also a winner.

One other quick thing I do is to wipe a thin coat of thinner on the surface. The irregularities will be the last thing to dry and will really stand out. Draw a pencil line around them so you won't forget.

I haven't fumed anything for decades, but my guess is that you are right about having to sand down the whole surface.

Jess

As others have mentioned...

John in NM

bright light, I like raking myself, but a variety of angles is a good plan too.

I also put a rinse of alcohol, mineral spirits, or even water over the wood before finishing. Like the first coat of finish, it will reveal things you missed. I like water in particular if I've been doing rasp work on something like a gunstock - the rasp teeth tend to compress the wood and if its then sanded flat and you go over it with a water based stain or finish you'll get raised tracks in some places where the teeth passed but you didn't sand down far enough. I believe this is what was really meant by "raising the grain"... but hell, ya can't argue with the internet so I just content myself with the belief alone

Re: Sanding to perfection question?  Need Help

Don Stephan

You didn't mention the sanding schedule. Not sure what should be the starting grit after the grinder but if I use 80 grit I follow with 120, 180, 220/240, 320. After 320 if i wipe the surface in small circles the fine sanding dust packs into coarse scratches, highlighting them. I think 400 does an even better job of packing into scratches and highlighting them.

Re: Sanding to perfection question?  Need Help

Barry Irby

I sculpted the butt print into the seats with a Harbor Freight carving disk 4 1/2" in diameter. It is very coarse. I smoothed it a bit with a 60 grit flap wheel on the grinder. Then I sanded with 60 grit on a 6" Festool Rotex sander. Actually, that fine tuned the sculpting. Then 80, 100 and 120. Then wet it to raise the grain and finished sanding on a five inch ROS at 220.

There was a lot of looking and feeling to get the lumps out and fair the curves. The sanders do a pretty good job of that.

Part of the problem is the seats are Quarter Sawn White Oak. Coarse grain with a lot of character and medulary rays. Lots of Stuff to hide scratches. I did four chair seats and a bench. Was trying to keep them very similar.

I am satisfied with the sanded surfaces as far as the 220 grit goes appearance wise except where I failed to see the scratches. Clearly needed to take the time and effort just before fuming them to see that there were spots that needed touching up.

At this point the defects may be left in place and become patina. These go with a table that was built to mimic an antique tavern table. The top of that was lightly sculpted with a plane with a curved blade to give it a very gentle scallop. Can't really see it but you can feel it. Considered "antiquing" the chairs with some intentional patina. Maybe I should have.

Re: Sanding to perfection question?  Need Help

AZ in Colorado Springs

Barry, if you went from 120 right to 220, I'd guess that's the problem. It's a big jump in grits. I don't skip grits.

I believe some on this forum have suggested 100, 150, 220, etc, but I don't do that myself. But going straight to 220, that's asking a lot of that finer abrasive.

Re: Sanding to perfection question?  Need Help

Barry Irby

No, that is not the case, at least this time, that is not what I am talking about here. On each chair I have a patch where I failed to notice scratches that were clearly left by the original grinding wheel. A little dish or depression that you could cover with a thumb print that got lost in the character of the oak.

I spent a lot of time "fairing" the seats, smoothing out even subtle high spots so the surface would appear to be long flowing curved surfaces without facets or bulges. These spots were missed by every abrasive after the grinding wheel.

I feel like this would have been a lot easier on a classic pine seat, for two reasons: the wood would have been a LOT softer and sanded to a "fair" surface much easier and there would be a lot less character in the pine to disguise the marks.

Another part to this is I was ready for this project to be over and to move on to the next one. I made four chairs and a matching bench. Lots of repetition. Sort of reached my limit. I should have disciplined myself to inspect them better.

Re: Sanding to perfection question?  Need Help

Don Stephan

I'm not sure 220 is fine enough when using a random orbit sander to avoid circular sanding scratches. My experience is it is necessary after the ROS to sand in linear fashion with the grain to remove 220 circular scratches.

Finish expecting...

david weaver

...that you may find something when finishing that you won't see without finishing.

I don't sand much, but when I do sand, I look at what I've sanded twice. Once with raking light in the shop, and if lucky, with daylight at some point, but if not, a second look with raking light. Sometimes the second look (spread apart by more than seconds) finds things - just something about how our brains work.

But you will still sometimes find things (because I sand rarely, it's more often scraper ripples or something of the like) you didn't expect to once you add the reflectivity of finish.

I almost always seal with shellac - padded or brushed, so spot removal, correction, and then pad shellac back on where spot removing - no problem.

Shellac is a pain to sand off, spot removal is always with a scraper if something was sanded, and then resand the spot so as not to load up a bunch of sandpaper and burnish or mark up a surface.