Sanding inside bowl during finishing

[Dean Center]

This is a small problem, but it's been bugging me a long time and I'm having trouble finding a solution.

In between coats of any film finish, I need to get rid of the accumulated bits of dust and debris trapped in the finish prior to the next coat. It's a very old house and there are plenty of nibs to remove. I've used scotchbrite gray pads, but don't find it does a very good job. 600-800 sandpaper works much better, but leaves scratches, presumably from the edges or corners of the paper. I've tried using sanding discs which seem to be better than sandpaper sheet material, but it still has edges and develops corners in use, so there are still scratch marks.

What do other folks use inside bowls between coats? Are there secrets to your method you'd be willing to share?

Thanks for the help.

 

[David Shombert]

I've found the so-called "wave" sanding discs to be better in this regard. Not perfect, but better than just the flat circular discs. They avoid the problem of the edge digging in. Plus, the ones that Packard sells come with the grit marked on every disc, which is helpful. You might also try a Mr. Clean MagicEraser pad; get 'em at the supermarket, use wet or dry.

 

[Richard Coers]

Sanding sponges. I buy 320 grit between from Vince. He has it up to 1500 grit. Never heard anyone say 600 and 800 leave scratches. http://vinceswoodnwonders.com/siasoft-paper-and-film-backed-abrasive/ Scotch Brite won't cut off nibs like abrasive paper, it takes sandpaper to get it flat and smooth.

 

[Mark Jundanian]

Dean, you might try wetting your sand paper with mineral spirits, if the most recent coat of finish is cured. You could also try Micro-Mesh Cushioned Abrasives. These are fine and hyperfine abrasives bonded to a foam substrate with rounded corners. (Note the micro mesh scale is different from sandpaper).



I use a gel varnish product and do not sand between coats. The product I use is Bartley Gel Stain Clear which is an alkyl resin, polyurethane blend. The application is a simple rag process. Wipe it on with the first rag, wipe off the excess with the second rag and hand buff with the third rag. Wait 6 hours then next coat.

My house is old, my finishing area is the other side of the shop and while I may let the air filter run for a bit, I don't take any particular precautions. It's a nice satin finish with no dust nibs. I have on the otherhand tried various General Finishes products, including the gel formula, and been beset with nibs.

I think the reason the Bartley product works is that it is very viscous--like pudding as compared to honey for other gels. And I think it has less solvents, or at least sets up faster. By the time I've buffed there is very little tackyness left and really no tackyness after an hour or two.

 

[musky]

Really hard to imagine where 600-800 would leave scratches that would show in the next finish coat. What you may be seeing is marks from your sandpaper if it has plugged up finish on it. 600-800 is probably too fine of a grit of sandpaper to use for sanding between coats. I usually stop at 320, but sometimes will go to 400, but no higher. If your finish is not really hard and curred, you will plug the paper when using the higher grits. If you see any dots of finish on your sandpaper when sanding, that more than likely is where your marks are coming from. Then again they possibly could be in your wood, under your finish, from the start, and will continue to keep showing through your finish coats. I'm really confused by your post though, are you talking about a wood turned bowl, or a house remodel?

 

[hockenbery]

Scotch brite grey. Usually dry.
With the grain.
I use Waterlox most of the time and it doesn’t collect nibs very much.

 

[robo hippy]

Supposedly, grits in the 600 to 800 range leave scratches that are invisible to the human eye. I would expect some thing else is causing the scratches. If you are using stiff paper backed abrasives, the paper can leave 80 grit scratches. If you are using an interface pad and the abrasive doesn't cover the edge with a little extra, the hook part of the pad can also leave 80 grit scratches.

robo hippy

 

[Dave Bunge]

In between coats of any film finish, I need to get rid of the accumulated bits of dust and debris trapped in the finish prior to the next coat....600-800 sandpaper works much better, but leaves scratches, presumably from the edges or corners of the paper. I've tried using sanding discs which seem to be better than sandpaper sheet material, but it still has edges and develops corners in use, so there are still scratch marks.

What do other folks use inside bowls between coats? Are there secrets to your method you'd be willing to share?

I've had similar experience with sandpaper. I'll use 600 grit to sand before the final coat on the outside of a bowl with no problems. But on the inside, it's hard to avoid getting scratches from the sandpaper. I think you're right, that the scratches are caused by the sandpaper edges or by the creases/corners the sandpaper gets from being pressed against a concave surface.

For shallow bowls, without much curvature, I'll still use sandpaper on the inside. I hand sand with the 2 3/8" blue flex discs from Vince, using the softest foam interface pad he sells. The pad is smaller diameter than the disc so that helps prevent the edges being pushed into the surface. I try to use a very light touch, and concentrate on the areas that have a nib to remove. On the bottom inside of bowl, I'll use the whole disc for sanding. Going up the walls, I grab the disc near one edge and sand with the opposite side of the paper, away from the edge of the paper, back where the edge of the foam backer pad it. Hope that was understandable. It just occurred to me that a 1" disc should have less tendency to crease, so I'll try that next time.

For bowls that have a lot of curvature, I use 0000 steel wool. The surface is not as smooth as I get with paper, but it also doesn't leave visible scratches. I'm just bought some of the Scotch-brite grey pads to try as well.

 

[Mark Jundanian]

Remind me again what the color sequence iswith the 3M pads? I thought white was the finest?

 

[Dave Bunge]

Remind me again what the color sequence is with the 3M pads? I thought white was the finest?

White is the finest. Here's what 3M states:

Color (3M number) Equivalent Grit
White (07445) 1200 - Finer
Gray (07448) 600 - 1000
Maroon (07447) 320 - 400

Table above from p.4 of brochure at this link: https://multimedia.3m.com/mws/media...ng-systems-for-paint-preparation-brochure.pdf

 

[Tom Gall]

Two things...or three. What type of finish are you using? Do you brush it on or put on with a cloth? Do you wipe it off at all?
1) Use a clean brush with no dried particles or a clean cloth (rotate) to apply.
2) If you apply the finish and wipe it off (building the finish) there shouldn't be much of a problem with dust nibs.
3) If you just lay it on (no wiping) try placing your wet bowl (or any turning) on a clean surface and cover it with a clean cardboard box (or other tent type covering) until the finish sets up.

 

[Dean Center]

Thanks for all the replies, with lots of interesting ideas. Some I've already tried. The AAW has surprisingly little content on finishing in the video part of Explore, but the short one from Curt Theobald where he recommends putting the finish on one side of the cloth, then flipping it over prior to wiping in order to allow the cloth to filter debris out of the finish has cut my nibs by about half, FWIW.

 

[Tim Tucker]

I've found the so-called "wave" sanding discs to be better in this regard. Not perfect, but better than just the flat circular discs. They avoid the problem of the edge digging in. Plus, the ones that Packard sells come with the grit marked on every disc, which is helpful. You might also try a Mr. Clean MagicEraser pad; get 'em at the supermarket, use wet or dry.

Can you elaborate on these - and the use of them? I am curious as to the purpose they can serve in finishing.
Thanks!
T

 

[Don Wattenhofer]

Steel wool or scotch brite because they completely conform to the surface and always use a tack rag to clean up before the next coat is applied.

 

[David Shombert]

Can you elaborate on these - and the use of them? I am curious as to the purpose they can serve in finishing.
Thanks!
T

They're foam pads that are very mildly abrasive. You can soak them in water and squeeze them almost-dry; that seems to work well for me. The guy who told me about them usually used them dry. The supermarkets have them in the cleaning supplies shelves, and Amazon has them: https://www.amazon.com/Mr-Clean-Dur...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=.

 

[Ronald Diamond]

I normally use Watco and normally do not sand between coats, but if I do not like the surface and want to touch it up, I use a 3" random orbital sander that I got at woodturners wonders, and wetsand using whatever I am going to finish with and a 1500 to 2500 grit disc. There seems little point in going this fine on wood, but on a finish surface it seems to work better than 800 or below. This works equally well with wipe on poly

 

[Tim Tucker]

They're foam pads that are very mildly abrasive. You can soak them in water and squeeze them almost-dry; that seems to work well for me. The guy who told me about them usually used them dry. The supermarkets have them in the cleaning supplies shelves, and Amazon has them: https://www.amazon.com/Mr-Clean-Durable-Cleaning-Durafoam/dp/B08492Q875/ref=sr_1_1_sspa?crid=1TFEDWWSMURXJ&dchild=1&keywords=mr+clean+magic+eraser&qid=1587859096&sprefix=Mr+Clean+,aps,292&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQUEyR1g2Sk1KQkFFJmVuY3J5cHRlZElkPUEwMjYzMTU4MkpIMTIxVDBCUkcyRyZlbmNyeXB0ZWRBZElkPUEwNTAzODEzMk1URlVPRzcyNUJaUyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=.

THANKS David!

 

[Kevin Weir]

With wipe-on poly, my routine on most bowls is to use the superfine steel wool in between coats. The final coat is applied very thinly. I have also experimented with a rotten stone and oil mixture. This tends to produce more of a matte finish.