Grit Choice for Sanding

Grit selection may vary depending on wood type and finish formula class. April 19, 2006

What grit sandpaper should I use to sand the sealer coat before the final finish?

Forum Responses
(Finishing Forum)
From contributor A:
I have had good results the last umteen years with 280 as my paper of choice. What grit have you been using?

From the original questioner:
I have been using 400.

From contributor B:
It may also depend on the wood. 400 may be sufficient for a closed grain wood such as maple, but for oak or mahogany you may want to step it down as low as 220. I have never used 400 so I can not tell you if what you have been using is acceptable, but I imagine if you have been eliminating the nubs and imperfections then you can continue to use it. Obviously if you lower the grit you will find the sanding will go a bit faster and you will experience less clogging of the paper.

From contributor C:
I agree - 220 up through 320 stearated paper depending on the woods being sanded.

From contributor D:
I think consideration should be given to the different type of coatings that are being used, as on evaporative coatings these coating will dissolve the sanding marks, whereas on reactive coatings courser sanding markings may show up as the coating dries out.

From the original questioner:
Thank you everyone for the input. This site has been a big help to me.

From contributor E:
To contributor D: What causes that difference?

To contributor E: The evaporative coatings open up and allow the each of the following coats to become a part of the first coat, these are one layer coatings regardless of how many coats you may apply, be they days or weeks later. Whereas, when reactive coatings dry, then you will be applying layer after layer because, these coatings do not resolvate.

So, sanding with the lower courser grit sandpapers the scratches will show up, because they will not reflow or amalgamate into the preceding coatings like the evaporative coatings do.

From contributor E:
To contributor D: I'd been thinking of the first coat over freshly sanded wood, and was trying to envision why evaporative and reactive finishes would, as classes, make a difference. I missed "dissolved" in your posting.