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Deep scratches in ply after staining

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Forum topic by tonychanman posted 05-16-2016 02:29 PM 459 views 0 times favorited 8 replies Add to Favorites Watch
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tonychanman

8 posts in 204 days


05-16-2016 02:29 PM

A bit of a rookie mistake on my part, but I’m using some Cherry plywood which I’m turning into a dining table. I cut it into an oval shape, laminated the edges then sanded the whole thing with a random orbital sander with 220 grit.

All looked fine so I went on to the finishing stage where I applied some wood conditioner. Then some scratches show up, getting really emphasized by the wood conditioner. I’m using a dark-ish stain so I thought it would hide the scratches, but nope it made them worse. The scratches go mostly against the grain and some of the are actually quite deep.

My first thought is to sand down and re-stain, however the cherry veneer on the plywood is quite thin so I’m afraid that if I sand it down, I’ll go right through the veneer.

I’ll post some photos of the scratches on Monday, but I think everyone probably has a good idea of what I’m describing.

Any help is greatly appreciated. Thanks in advance.


8 replies so far

View rwe2156's profile

rwe2156

2192 posts in 943 days


#1 posted 05-16-2016 02:44 PM

Oops. Hate to say it, but this will be tough one to salvage. Once stain has penetrated a scratch you’re usually done with plywood.

I would probably overlay it with a new piece of 1/4” cherry ply and start over.

FWIW I rarely use a ROS sander, in fact I avoid it like the plague, especially in hardwoods. Probably also has to do with quality of sander.

With ply I just hand sand LIGHTLY with the grain using a sanding block and being extra careful at the edges.

-- Everything is a prototype thats why its one of a kind!!

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tool49

6 posts in 212 days


#2 posted 05-16-2016 03:07 PM

My experience has improved tremendously once I stopped trying to sand faster and actually letting the sander do it’s job.

Running through the grits and letting the surface improve with each pass. Another thing is to start low enough in the grits, removing router dragging scratches with 220grit will take all day and actually polish the surroundings of the scratches and make them look worse. Going back down to 80 grit will remove those scratches within a minute per square foot and moving up to 100, then 120, about 1 minute per square foot each grit.

Obviously on plywood you don’t get too many start overs but still. Are the scratches the common pig tail swirls or some other marks left by previous manipulations?

I would try to sand lightly (just the weight of the sander, no pressure or hardly any) everywhere again with a lowish grit (I would start at 100 to not eat through the veneer too fast) to remove the scratches, no other choice at this point… If it fails, you could always glue a cherry veneer on top of your plywood…

Spotting those scratches before staining is tough, do you have a good raking light? Before staining I also like to run mineral spirits on the surface on critical spots and scratches usually stick out better.

Hope this helps.

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tonychanman

8 posts in 204 days


#3 posted 05-16-2016 04:40 PM

This is certainly a lesson learned. I saw the scratches show up when I applied the wood conditioner and should have stopped there to resand the plywood before applying the stain.

I’m quite certain these are scratches from the factory/store. They’re not scratches from my ROS, looks like something was placed on top and then dragged. I’m using a Festool ROS with 220 grit which I’ve done many times in the past, I just missed the scratches this time.

I’m really hoping for a solution to salvage the piece rather than redoing the entire table top. It’s 42”x84” so not a small project. I can’t add a veneer to such a big piece since I don’t have a veneer clamp large enough for that. The Cherry plywood was not cheap enough for me to just buy another sheet either. I could but it would be really eating into my profits.

Is there any chance I can fill these scratches with something and then stain over to minimize their appearance? I’m thinking like some sort of putty or filler. Even applying it with a fine tool into each individual scratch, lightly sand to blend it in then stain again?

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devann

2200 posts in 2155 days


#4 posted 05-16-2016 04:44 PM

It sounds like if you want to salvage your plywood you’re at the touch-up phase. It’s not a good place to be, especially for those not experienced with the art of proper touch-up. You could be at a good place to start learning, what do you have to lose? You’re probably going to have to replace the plywood anyway. Sorry to sound so pessimistic but that’s the reality of where you are as per your explanation about your project.

Applying a veneer or high end plastic laminate is another option. Cost and end use are the considerations for these options. You’ll probably have to make a bullnose for the edges to hide the transition. I’m betting you were doing so kind of edge treatment anyway.

The good news is you’ve learned something.

When making something nice that is a stain grade finish, I like to wipe over the surface with a slightly damp cloth. Don’t get the cloth too wet, you don’t want to damage the wood. Mineral spirits is another option, be careful using near glue joints, again use as little as possible. The dampness will reveal all of the small scratches you thought were eliminated by sanding. Allow to dry and sand accordingly.

-- Darrell, making more sawdust than I know what to do with

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jbay

812 posts in 361 days


#5 posted 05-16-2016 06:03 PM

Photo’s might tell a different story, but without seeing it, I would wipe it all down with lacquer thinner and try to sand them out. Of course it depends how deep they are and how thick your veneer is and how talented you are being careful not to sand through.
Plan B would be to veneer over the top.
Plan C….Start Over
Plan D…Paint
:>/

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

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tonychanman

8 posts in 204 days


#6 posted 05-16-2016 08:46 PM

Do I need to use lacquer thinner even though I’ve only stained it so far? I would have though I could just start sanding right away.

View jbay's profile

jbay

812 posts in 361 days


#7 posted 05-16-2016 09:12 PM

The stain will just clog the sandpaper. try it and learn first hand. If it sands go for it, if it don’t, clean it with the lacquer thinner and try. Nothing to lose, knowledge to gain. These are school lessons, take advantage of the course. :)

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

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tonychanman

8 posts in 204 days


#8 posted 05-16-2016 10:05 PM

Well I tried to sand it down and sure enough, by the time I sanded out the scratch I was through the veneer. Time for a new sheet :(

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