Sanding vs screening

[Rob Blaustein]

I did some searching here on this question but I'm still not sure I understand the difference between using say 100 grit sandpaper and 100 grit screen. I ask because I'm going to try my hand at some floor refinishing in a small room (around 8' x 9') and the instructions on the finish (Bona Mega--a waterborne finish) for prepping the surface read:


"For a stained floor, make your final cut with 80-100 grit paper and screen to 80-100 grit. For an unstained floor, make your final cut with 80-100 grit paper and disc/screen to 120-150 grit. This burnishing will reduce the amount of grain raise."

Now it's a bit academic because I don't actually have anything that will accept screens since I'm going to try to use my 6" random orbit sander for the sanding (hooked to a vac). The floor isn't in too bad shape but I will have to sand off the old finish. I was going to try 36, maybe 50, 80, 100 or 120 grits (but I'm open to suggestions), then stain, then a few coats of finish. Is there some equivalent substitute sandpaper grit that I can use to get the same effect as the 100 grit screen?

--Rob

[Doug Shepard]

I'd never even heard of sanding screen until an ex-neighbor who was a building contractor gave me some 180g screen when I was working a particularly non-flat plane sole. Cant tell you what it does on wood but it significantly sped up the metal sanding. I believe it's due to the swarf being cleared out by falling through the screen holes. You might want to wet down the floor after sanding then hit it again after it dries to knock down the raised grain.

[Charlie Plesums]

If screen is Mirka Abranet, that is a wonderful version of sandpaper, but I don't understand the instructions you listed in this context.

I started using Abranet in 600 and 800 grit because it was hard to find a non-sterated paper in that grit, and fell in love with it. It does not clog, and lasts far longer than traditional paper. I have a sample pack with a variety of grits, and will probably go to it for most grits as I use up my inventory of conventional paper.

If you have a Festool sander, the hooks in their hook and loop are extra long, and extend through the screen, and are sanded off. It didn't take long for me to have frisbees instead of sanding discs. I replaced my festool pad with a Mirka pad that has perhaps 50 or more holes... lots of small holes for the screens, 9 holes for the standard Festool paper, plus 6 holes for the standard 6 inch sandpaper. I love my Festool sander even better now.

[Rob Blaustein]

Charlie--there was no spec re type of screen. From what I've seen searching around about floor refinishing, the use of screens is common for that purpose. I think this is a question for the flooring gurus.

[Doug Shepard]

Apparently the finer grit screens are pretty standard with drywallers. The stuff my neighbor gave me was something left behind on one of his jobs by a drywall crew.

[Charlie Plesums]

When I was looking for a good price for Abranet sanding discs (the stuff I love, which looks like a screen backing with abrasive) someone referred me to this place which sells the Abranet at a good price, and also sells screens.
www.supergrit.com/products/products_sheets-sandscreen.asp

I haven't determined if the screens are the same material as Abranet but in sheet form - if you go down that path, I would love to learn

[Matthew Poeller]

I am not sure about the difference in the screen versus abbrasive and what not but I have been redoing my floors room by room in the house with great success.

These are the origianl white oak floors and they are all surface nailed.

Tools:

Varathane Sqar Buff Sander (jitterbug)
5" ROS Sander (6" would be nice but I do not have one)
Bona Kemi Bona Seal
Bona Kemi Mega

Process:
36 grit on the jitterbug (tried 20 on one floor but the scratching that it left took me too long to get out, but to just stick with the 36 and spend more time if needed)
60 grit
80 grit
100 grit

Vacuum, wash, surgically clean (unless you have a dog, then just pray)

Apply Bonaseal

After dry, knock the grain down (waterbased raised grain) with 150 grit in the ROS (yes longer than if you were to use the scotchbrite pad on the jitterbug but cheaper since I did not have to keep the sander the extra day).

After that vacuum and damp mop apply Mega. I have been doing 3 coats with about 24 hours of dry time in between and that leaves a very nice finish on the floor.

I could be all wrong and the floor gurus may laugh at me but this has been working. My wife likes it and I like it and I am pretty anal retentive.

Matt

[Jason Roehl]

Here's my take, having finished quite a few floors. You're going to hate it if the only tool you use is an ROS, especially if you plan on staining the floor. The bottom line is that an ROS just doesn't remove much material, finish or wood, even using 36 grit (been there, done that...with a Rotex in aggressive mode). You're going to have a hard time getting all the finish off so that the stain will go on evenly. Not impossible, it will just take a long time and a lot of sandpaper.

As for screening, those are used on 16-17" floor machines--like the ones used for buffing floors, only low speed (ours is 175/300 RPM) We use a burgundy 3M scratch pad attached to the hook pad of the machine, and then that burgundy pad grabs the sanding screen.

For staining, the key is that during sanding you have to remove all the scratches from the previous grit. Since you're sanding with such a small device, be a Southerner--don't skip any grits. When you get to staining, keep a piece of 100 grit sandpaper in your pocket, so that if you see some egregious scratch marks highlighted by the stain, just sand in the stain at that spot parallel to the grain. It's amazing how well this works.

Your knees and back are going to think that room is 60'x60' by the time you're done...

BTW, I have put on a coat of shellac and 3 coats of Mega in under 8 hours on ~1100 s.f. of floor before. That's definitely pushing the dry times (dry air, high temps), but it works.

[Howard Acheson]

Screens are used for sanding floors as they do not clog as readily and can be cleaned by banging them on the floor mostly.

Now, let me strongly suggest that you use a commercial floor sander, not your own hand sander. If you plan to stain, you must get all the old finish off including that which is deep in the pores. Most small ROS sanders do not do a good enough job and the staining ends up uneven do to the residual finish in the pores. Many places rent the floor sanders and it will make the job a lot easier.

[Rob Blaustein]

Thanks for all the replies. I'll try some test spots tonight with my ROS and see if I make any headway. Depending on how this goes, I may end up rending a U-sand which people have found helpful. But my sense is that that machine uses 4 random orbit sanders at once. If that's the case, then it seems that one hand-held ROS should be able to accomplish the task, though perhaps much less quickly and with more back and knee pain.

[Andrew Long]

Thanks for all the replies. I'll try some test spots tonight with my ROS and see if I make any headway. Depending on how this goes, I may end up rending a U-sand which people have found helpful. But my sense is that that machine uses 4 random orbit sanders at once. If that's the case, then it seems that one hand-held ROS should be able to accomplish the task, though perhaps much less quickly and with more back and knee pain.

I used the U-sand unit to do my floors. Yes it is four 6 inch ROS... absolutely NO comparision to the hand held ROS we use for project finishing. And that comes from someone whom owns a Festool 6" ETS, which is the most versatile ROS I've experienced. I wouldn't consider using my hand held ROS for a real floor project, unless I was doing a very small room or closet and I had a ton of spare time (I don't).

Do yourself a favor, rent the U-Sand, I believe there around $60 for 24 hours where I live. You can get a lot more work done with those babies; use an assortment of grits depending on what your starting to get them baby behind smooth (a big plus -barely any dust). You typically need at least 3 grits to get a nice finish grade, possibly a fourth if you cutting down old worn floors and removing finish.

[Rob Blaustein]

Well given the results of the experiment I just did, I'm going to have to agree with the advice that Jason, Howie, and Andrew provided and not try to do this room with my ROS. I ordered some 40 grit Cristal paper for my Festool ETS 150/3 sander and it just came today. Although it did remove a lot of the old finish I can see that removing ALL of it will be way too time consuming. It took me a while and I still couldn't totally flatten and remove the finish in a 1' x 2' area in the closet. So it's either a Rotex, which I'd have to buy, or rent the U-sand. I haven't needed a Rotex for anything yet, and it is pretty pricey, so I think the U-sand is the way to go here.

If I rent it for a day to do all the sanding, would I also need it for any buffing in between stain or coats of finish, or could I do this by hand with a maroon pad (or the ROS)? I'd rather not have to keep for 2 days.

--Rob

[michael osadchuk]

[QUOTE

If I rent it for a day to do all the sanding, would I also need it for any buffing in between stain or coats of finish, or could I do this by hand with a maroon pad (or the ROS)? I'd rather not have to keep for 2 days.

--Rob[/QUOTE]

rob,

I believe Matthew answered this question (smiley)

michael

[Rob Blaustein]

[QUOTE

If I rent it for a day to do all the sanding, would I also need it for any buffing in between stain or coats of finish, or could I do this by hand with a maroon pad (or the ROS)? I'd rather not have to keep for 2 days.

--Rob

rob,

I believe Matthew answered this question (smiley)

michael

Ah yes--thanks for pointing that out. Not sure why I didn't remember it, it was only a few posts ago.:confused:

[Jason Roehl]

Rob, if you're staining, I wouldn't do any sanding between coats of finish--only before the last coat. One coat of finish is not very thick, and it's very easy to sand through that and the stain. I never power-sand once finish is down, either--the finish is just too soft for that to work well (BTDT). A pole sander with 3M green sandpaper (150-220 grit) goes pretty quick and takes off any dust nibs handily. Of course, you have to vacuum and damp-mop carefully after that.

P.S. Rob, I got your PM, I just figured I'd keep the discussion here so that questions and answers can benefit everyone!

[Rob Blaustein]

Thanks for the additional tips Jason!

[Rob Blaustein]

I had a nice conversation with a tech person at Bona the other day. He was very nice and also quite helpful. I had a few questions about using their stain and Mega finish and I then asked him about sanding vs screening. His suggestion, if staining, was to sand to 100 or 120, then screen with 100. He said the higher the grit of sandpaper one uses the more one closes the pore and burnishes the wood, and the less the stain will penetrate. That matched what I've read and experienced. But he said that using a 100 grit screen opens the pores up without disturbing the level of prior finish (this I found a bit confusing) and allowed the finish to penetrate better. He also said sandpaper won't conform to the floor and so will level it. But the screen is usually placed on a cushioned surface like a synthetic buffing disc (like the 3M pads) placed on the ROS pad sander or buffer, and it will therefore form a more flexible surface that will conform to the floor so won't level it.

[Jason Roehl]

That's all good, Rob, save for one thing, and this is from experience. 120-grit screens are better than 100-grit screens. 100-grit screens just leave too many scratches and shed a lot more of the abrasive grit. The tech is right about the sandpaper vs. screens, but that doesn't mean screens will get down in everything. If you leave a little divot somewhere, you'll see it when you screen because the fine dust will settle in there.

[michael osadchuk]

I had a nice conversation with a tech person at Bona the other day. He was very nice and also quite helpful. I had a few questions about using their stain and Mega finish and I then asked him about sanding vs screening. His suggestion, if staining, was to sand to 100 or 120, then screen with 100. He said the higher the grit of sandpaper one uses the more one closes the pore and burnishes the wood, and the less the stain will penetrate. That matched what I've read and experienced. But he said that using a 100 grit screen opens the pores up without disturbing the level of prior finish (this I found a bit confusing) and allowed the finish to penetrate better. He also said sandpaper won't conform to the floor and so will level it. But the screen is usually placed on a cushioned surface like a synthetic buffing disc (like the 3M pads) placed on the ROS pad sander or buffer, and it will therefore form a more flexible surface that will conform to the floor so won't level it.

Rob,

Two comments, one on sanding, the other on staining.

I wonder if the Bona representative was talking about the use, typically by professional flooring workers, of screening on ROTARY sanders with a hard platen, as a second step following the use of a BELTED sanding machine; a flat, hard platen on a rotary sander will obviously not follow any remaining contours in the floors and therefore would do the final levelling of the floor before any finish is applied. The third step would be the use of screening on the same rotary machine, but with a soft platen, which would follow the floor contours - and therefore be less likely to cut into finish you have applied - to remove dust nubs and provide some "tooth" or grip to suceeding finish coats if using a polyurethane finish.
If you are using the U-Sand - with 4 rotary sanding heads - you would be doing the above "steps" one and two with that machine.
This is my 'guess' at reconciling the information you received from the Bona rep with what you already knew. Others here may be better informed.

Staining.......
When I tried to use stain on a large Murphy bed project made with oak, I was unhappy with with the uneveness of the color - swirls, etc.
Then I tried some water based dye - from Lee Valley - and achieved a much more controlled and even application of the color.
I gather that the difference between a dye and stain is that the color granules is the dye are much smaller than in a stain and therefore penetrate the wood while a stain sits on top of the wood.

I think in the U.S. a popular dye is called trans tint or something along those lines.
The LV dyes are sold in one once packets of dry powder which is dissolved in water..... one packet would be enough for the room size you are doing.

I gather with stains some woods are more difficult to color so if using a stain, it would be more important than usual to do a trial (on a piece of closet flooring perhaps)

good luck

michael

[Rob Blaustein]

Thanks for the comments, Jason and Michael. I think I'll not end up using screens and just go with sanding, probably to 120 since I don't want too much stain to absorb. That seemed to work well in a small test area.

As to stains--I'm sticking with the Bona stain since the compay has tested it extensively with their finishes and know it works well. I have used transtint dyes and others on ww'ing projects with waterborne finishes, often with shellac, and like them but for this flooring project I'll stick to the Bona combo.