staining cherry plywood, lines showing up.

[Dennis Jarchow]

I had a bunch of cherry cabinet and bar parts stained and sprayed by a finisher at his shop. I had to stain the tops of the cherry columns on the bar myself as they surround steel columns and the finisher will spray them onsite. They were stained with Old Masters oil based wiping stain and will be sprayed with Gemini GemVar conversion varnish. The columns, which are cherry plywood, were machine sanded through 180 grit and then a final sand by hand with 180. On one side of one column, I got some light/dark sections that showed up when I stained them. The sections have pretty distinct straight horizontal boundaries. It doesn't look like the normal blotching you get with cherry. I am attaching a picture and you can see it in the lower half of the picture.

I tried applying some more stain to the lighter sections and all it was doing was making the neighboring darker parts darker but not affecting the lighter parts much. Any suggestions? Thanks

Column_stain.jpg

[Kevin Jenness]

I suspect incipient sandthrough. What was your sanding sequence? Did you run the plywood through a widebelt? Is the core veneer or something more uniform? Looks to me like you are just a few thousandths above the glueline in the light areas and the glue-saturated wood is rejecting the stain. As thin as the baloney is sliced these days there is not a lot there to sand after the factory gets through with it.

[Kent A Bathurst]

I'd try a sealcoat. May not be blotch, but it is giving me the same vibes in the photo, so maybe the same approach will solve it.

I always-always start cherry with 2 coats of 3/4# - 1# dewaxed ultra pale [etc] shellac. I pad on 2 coats, with the 2d reversing across the same path, so I get even coverage. Then barely scuff sand with 600g.

Or another seal coat material - I don't know them because shellac has worked so well for me, never felt a need to try.

[Dennis Jarchow]

I suspect incipient sandthrough. What was your sanding sequence? Did you run the plywood through a widebelt? Is the core veneer or something more uniform? Looks to me like you are just a few thousandths above the glueline in the light areas and the glue-saturated wood is rejecting the stain. As thin as the baloney is sliced these days there is not a lot there to sand after the factory gets through with it.

Plywood is combi core so there are mdf layers under the veneer and then veneer core in the middle. I used the same sanding sequence I used on the rest of the column and all of the other cherry plywood panels in the bar. Light sanding with 180 grit on the orbital, then a light hand sand with 180. This is the only one with issues.

Thanks!

[John TenEyck]

I think Kevin is right. The veneer is incredibly thin, and you sanded down into glue saturated areas. 180 grit with a ROS on commercial hardwood plywood is like playing Russian roulette. It's already been sanded to 320 or something similar. No need to start coarser, and not much need to start at all. Hand sand, lightly, with 320 grit and begin your finishing process.

Making it all look consistent is not going to be easy. I might think about using a mini sprayer/air brush and spraying a shellac toner on the light areas. That should get you close w/o darkening the darker areas. Then seal it all with a light coat of rattle can shellac. If the light spots are still too light, you could spray more shellac toner or try a gel stain or glaze and dry brush.

Or rip it out and start over.

John

[Kevin Jenness]

Plywood is combi core so there are mdf layers under the veneer and then veneer core in the middle. I used the same sanding sequence I used on the rest of the column and all of the other cherry plywood panels in the bar. Light sanding with 180 grit on the orbital, then a light hand sand with 180. This is the only one with issues.

Thanks!

That actually is similar to what I would have done, though I would typically end with 220 on the random orbit instead of hand sanding. When you said "machine sanded" I wrongly inferred use of a wide belt sander. You may have just come across a bad sheet with thinner veneer, or perhaps there is something else going on with those veneer leaves. I suspect you are going to have to replace that section. Maybe your finisher can seal the surface and tone it with tinted lacquer.

[Dennis Jarchow]

I applied some more stain like a glaze with a fine brush and then used a dry brush to blend it in. That minimized the differences. While not discounting sanding too much (I have a little of that on one of the mitered edges) the thing I noticed is that the darker/lighter bands are symmetrical with the bookmatch veneer seams, and while this was the worst offender I can see some of it on both columns. I found a scrap piece of the same plywood that had never been sanded. I sanded half of it, and stained the whole thing, and got the same look, though not as pronounced depending on the viewing angle. The good thing is my finisher came yesterday and sprayed both columns and the conversion varnish helped to blend in my repairs and things look pretty good.

Thanks for every one's help.

[John TenEyck]

I applied some more stain like a glaze with a fine brush and then used a dry brush to blend it in. That minimized the differences. While not discounting sanding too much (I have a little of that on one of the mitered edges) the thing I noticed is that the darker/lighter bands are symmetrical with the bookmatch veneer seams, and while this was the worst offender I can see some of it on both columns. I found a scrap piece of the same plywood that had never been sanded. I sanded half of it, and stained the whole thing, and got the same look, though not as pronounced depending on the viewing angle. The good thing is my finisher came yesterday and sprayed both columns and the conversion varnish helped to blend in my repairs and things look pretty good.

Thanks for every one's help.

Glad it turned out well, Dennis. Having a bag of repair options can often overcome such problems. Nice save.

I wonder if the veneer seaming caused it to be higher off the substrate along the seam, then when you sanded it, it would end up thinner?


John

[glenn bradley]

I found a scrap piece of the same plywood that had never been sanded. I sanded half of it, and stained the whole thing, and got the same look, though not as pronounced depending on the viewing angle.

Glad it worked out. So, it sounds like that specific material was going to do that to some degree no matter what. Obviously one to put on your "don't buy" list. I think we all run into one source/product or another that we don't go back to.