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I bought a Jarvis/Fully bamboo desktop and am trying to darken the finish.

To do this, I started on the bottom of the desktop and tried out the steps on a small portion by:

  1. first sanding away the previous finish
  2. applying two coats of Varathane Gel Stain (picture attached), waiting a day or so before applying the 2nd coat.
  3. putting on 5 layers of Varathane water-based interior polyurethane, waiting 2-6 hours between coats.

I noticed the grain is a bit raised. This could be because I did not sand enough before putting on the gel stain or because the poly raised the grain. I don't remember how much I sanded to begin with, so I cannot say for sure. Regardless, I tried lightly sanding a spot with 220 grit sandpaper, against the grain (it was just a test, I know I shouldn't do this for the real thing), and I lightly sanded another spot with 400 grit sandpaper. In both cases, the sandpaper just about immediately took off some of the gel stain.

Is this likely due to the stain being a gel stain, which sits more on top of the surface than a traditional/real stain? Or do you suspect there is a different issue?

Note: my thought is that, for the real project, I will make sure to sand the surface up to a very high grit so the surface is very smooth. But this will not prevent the grain raise, if that was the issue in the first place. If there is grain raise, I'd like to be able to smooth it out.

lightly sanding with 400 grit with the grain (notice that some stain has been removed): lightly sanding with 400 grit with the grain (notice that some stain has been removed)

lightly sanding with 220 grit against the grain (notice that some stain has been removed): lightly sanding with 220 grit against the grain (notice that some stain has been removed)

Varathane Gel Stain (Kona): Varathane Gel Stain (Kona)

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    Even without the photo to go on (which appears to show very characteristic sanding/scuffing marks) there's no way you got through five coats of WB poly and through the gel stain to reveal bare bamboo with some light swipes using 400-grit paper. This would be unlikely even with the 220 (which is really much too coarse to use to safely sand finish). Wet a finger with saliva, swipe over the grey marks and they should instantly vanish.
    – Graphus
    Oct 16, 2022 at 12:57
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    "I will make sure to sand the surface up to a very high grit so the surface is very smooth." You don't want to do that, especially when colouring wood. We actually have Answers here that cover what the final sanding grit should generally be, both when staining and not, that you could do with hunting down. Additionally plenty of Answers touch on raised grain and how to prevent it or deal with it, as well as on how to sand finish. After you've read over those see if you think this Question is actually still necessary (bear in mind that SE doesn't allow duplicate Qs).
    – Graphus
    Oct 16, 2022 at 12:59

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Water-based poly will raise the grain, there's nothing to be done about that. You just have to make sure you lightly sand between coats - especially after the first coat.

I'm not 100% sure, but I don't think you actually removed the stain by sanding it. The sanded parts just look lighter because the surface is scuffed up. I bet if you put on another coat of poly, it'll darken again. Try it - if I'm wrong, all you've lost is a few cents worth of poly.

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    I re-read your post and noticed that you put on 5 coats of poly. 5 is a lot - a more typical number is 3. There's no way you went through 5 coats with some light hand-sanding.
    – Mike Baranczak
    Oct 16, 2022 at 12:35

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