Sanding/finishing plywood

[motorhead9999]

I'm in the last stages of building a desk, and sanding/finishing is right around the corner. I've never finished plywood before, and I'm a bit nervous with screwing it up. I'm using a cabinet grade maple plywood with solid maple edge strips along it. I'm using a General Finishes Gel stain. Per General Finishes, "For softwoods such as pine, aspen, or alder, sand first with a #120 grit sandpaper, and finish sanding using #150 or #180 grit sandpaper. For closed grained hardwoods such as Oak, Maple or Birch, start with #100 sandpaper and finish with no finer than #120 sandpaper."

1) I have a Rotex 150 and an ETS 125. From what I've read, the Rotex isn't the best choice for this type work, and I'd be better off using my ETS 125. Is this true?

2) What settings on my ETS (or Rotex) should I use?

3) Being that it's maple, this suggests I should do 100/125 grit. But does it being plywood make a difference? Should I use those grits, or use the 120/180 option?

4) Any other tips or tricks when doing plywood?

 

[squall_line]

1. The only reason not to use the Rotex is if it's broken and can't be switched out of Rotary mode, and/or you have hundreds of square feet to sand.  Otherwise, you can sand without issue in random orbit mode and you have the advantage of a 6" disc, which is 44% larger than a 5" disc.  The trick is finding the right balance with the sander, as it can be a little large and unwieldy.

2. Use random orbit on the Rotex.  I don't have a speed recommendation for either sander (that's the only other setting I know of).

I'll leave 3 & 4 to others with more experience.

 

[Packard]

Make a test on the plywood with each grit to see how long it takes to sand through the surface veneer.  That will give you an indication of how much time you have for sanding.

Since the Pandemic, I have found that commodity veneers (red oak and maple) have become very, very thin and easy to sand through.

 

[Sparktrician]

First, watch this video and pay careful attention. 


Second, back the suction from your dust extractor down by 65-75% so you don't get sanding swirls in the plywood.  A Rotex will eat through the finish veneer ply VERY quickly, if you don't. 

YMMV...  [smile]

 

[Crazyraceguy]

Hitting on 3) and 4)

Stick with what the manufacturer says on the stain. They know what works best, through countless hours of testing. Too coarse will show scratches and pig-tails, too fine just burnishes the pores closed. Then the stain has nothing to grip onto.

 

[motorhead9999]

Hitting on 3) and 4)

Stick with what the manufacturer says on the stain. They know what works best, through countless hours of testing. Too coarse will show scratches and pig-tails, too fine just burnishes the pores closed. Then the stain has nothing to grip onto.

I guess that's where I'm a bit confused though. There's the two different scenarios (100/120 or 120/150). I'm pretty sure my plywood would be considered a softwood (even though it's maple) and would call for the 120/150 option, but then it specifically calls out maple for the other sanding grit combo. And then there's the fact that I have the hardwood edging around it, adding to the confusion. Which should I stick with?

 

[Michael Kellough]

With the thinness of face veneer on plywood these days I’d start with 180, but I seldom use stain.

120 grit on a sander is more likely to cut through and also leave scratches that are against the grain.

If I did want to use stain on plywood I’d probably hand sand with the grain at 150 since hand sanding generally makes deeper scratches than a machine at the same grit. So the scratches will be sufficient to hold the stain and they won’t be terribly noticeable since they’re parallel to the grain.

If you do want to use a machine use the gentler ETS 125.

 

[Cheese]

Wow... there have been many solutions contributed on this thread to your situation.  [smile]

120 grit is much too coarse for the thin veneer thicknesses we're forced to work with on the current veneered surfaces. I work in the 180-220 range when sanding veneer and that works well. Ya it may be a bit slow but at least you'll know when you're starting to sand through the veneer.

 

[smorgasbord]

Probably worth mentioning that most hardwood plywood is pre-sanded to a higher grit than 120.

 

[Packard]

I use a penetrating oil based stain, so I would not pretend to know how to prep sand for gel.

Luckily, there are huge amounts written on the subject online and a brief scanning of a few of the sites shows that much that is written in this thread matches other sites’ info.
https://www.google.com/search?q=sanding wood for gel stain&ie=utf-8&oe=utf-8&client=firefox-b-1-m

My problem with gel stain is based on my observation of the store fixtures in the local Barnes & Noble.  At every place where to wood is even slightly worn, a almost-white appearing substrate is visible.  That would not happen with penetrating stains.

If I were using a gel stain, I think I would first use a penetrating stain to prevent that wear-through look.

The big hit on penetrating stains is the tendency to blotch with certain wood species (pine and maple come to mind).  So if that is the concern, make tests first.

Cabinet.com’s article on staining tight grained wood is well-presented. (They do not recommend stains, but rather prefer dyes.  Read below:
https://www.cabinetdoors.com/blog/t...XU4XJq32bxtbCVYfnN7iTD8AWfaL5FSVunGQUrBOKMO4B

When I am working with a wood that potentially will have a blotchy stain result, I fall back on the suggestion that Norm Abrams gave me:  Use Minwax’s Polyshades, a finish and stain in one.  I’ve used that and it 100% works.

Note:  I met Norm Abrams at the National Hardware Show where he was hired to help out at the booth next to ours.  This was back in the early to mid 1980s.  He was as easily to talk to as you might assume from watching his shows.  A nice guy who seemed to know what he was talking about.

 

[Packard]

Here is a presentable looking display at Barnes & Noble.  I believe it was stained with a semi-transparent gel stain. 

Here’s what you see at a 6 foot distance:

And here’s what you see when you go to select a book:

I do believe that a big company manufacturing large quantities, did not use a wipe on gel stain.  I believe this is sprayed on, much like a semi-transparent paint would be.  It would then be top coated (I would hope).

In any case, a penetrating stain would present a nearly identical color when the top coat is chipped off, and the damage would not be anywhere near as obvious.  At this point B & N looks to be under-maintained, which might be the case as B & N has had a hard time competing with Amazon.

I would note that larger radii at the edges would be far less prone to this type of damage, and if your design allows for it, and if your application will see hard use, would be something to consider.

Right now, I am only considering the very decent cup of coffee that they serve in the cafe.

 

[Crazyraceguy]

Those stripes you see on that veneer plywood are a result of the way it is cut. I don't know why, but something happens when it is bookmatched. One half is almost always darker than the other, sometimes it is subtle, maybe not even visible until the finish is applied. Stained or not, it can show.
Slipmatched or rotary cut ply doesn't do this, but of course rotary is ugly and usually only done on softwood.
I thought I had a pic of a job I did several years ago, but I can't find it. It is simple clear coated Maple, and this shows on it pretty badly.