Corduroy texture on Adirondack top?

[PhilQ]

Well, this is my first build with a red spruce top. So far I had only used cedar or sitka. When I finish-sanded the top down to 220 or 320 before finishing, it was perfectly smooth. I french-polished the top with shellac as I usually do and it looked great. I let it cure for a couple days before leveling the shellac, and when I got back to it, you could see and feel ridges on the top following the grain lines. I decided to sand through the shellac, to the wood, and re-smoothed everything. Re-finished. A week later, same thing.

So I kept going, finished my french polish, and leveled at the end, but because of the ridges, the sandpaper hit the high spots more than the low (of course) and I ended up with differences in color. I fixed that as best as I could and let it cure for almost three weeks before I would do a final polish on it. Just got back to it this morning, and the ridges are back. It's like they always want to pop up. And when I sand, I hit the ridges again, and accidently went to bare wood on the ridges again. Frustrating.

What can this be due to? It looks to me (now, I didn't realize it at the time), that the top isn't perfectly quartered. The grain lines are straight and go vertically up and down the top, but looking at the end grain, it's like they are cut on a slight bias. Could this be the reason?

Humidity is pretty constant in the room and has been the whole time...

Thank you

[WaddyT]

Pretty much standard fare for a French polished top. Sometimes it helps to seal the top with egg white and sand back a little before putting any shellac on it. It would also do that less if you didn't sand the top, but did your final prep with scrapers or a hand plane with very sharp blade. Sandpaper tends to sand deeper in the soft wood between the grain lines.

[PhilQ]

i did use a scraper, but finished with sandpaper. I wonder why this never happened with other tops. Maybe because the grain lines are pretty far apart on this one?

Strange that it looks dead flat after sanding, and the texture reappears later...

[Ned Milburn]

Originally Posted by WaddyT

Sandpaper tends to sand deeper in the soft wood between the grain lines.

And scrapers can do the opposite, leaving the between-the-grain to spring up higher than the grain lines.

Either method requires a delicate and fine touch at the end. But, also, finished wood will often show its grain lines. Nitro finishes do this, and even plastic finishes put on thin will do this.

After you have a build of shellac, it is usually not advisable to sand or else you run into issues including those you have experienced and reported.

[PhilQ]

Originally Posted by Ned Milburn

And scrapers can do the opposite, leaving the between-the-grain to spring up higher than the grain lines.

Either method requires a delicate and fine touch at the end. But, also, finished wood will often show its grain lines. Nitro finishes do this, and even plastic finishes put on thin will do this.

After you have a build of shellac, it is usually not advisable to sand or else you run into issues including those you have experienced and reported.

Thanks Ned. I was following the method on LMI and trying to level the finish.