Sand to what?


Marmotjr

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I've noticed a lot of people on the net state they only sand to 120 or 180 before applying a finish.   I've found I like to go to 320, 400, or even 600, especially with pens or other work on a lathe.  The higher grits offer such a smoother feel and look to the wood.  What I am missing here? 

I'm guessing they are using the finish to cover up any imperfections left on the wood, but wouldn't a smoother starting surface allow for less coats?   Or am I just making more work for myself? 

 

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Your final grit will depend on so many things. If I stopped at 180 on a walnut panel you would see every scratch mark when the finish hit. On some harder woods too high a grit will burnish the surface and change the effect of the finish. I exploit this to make exposed end grain match face grain.

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It may just be that I'm in a very humid climate, but I find that sanding beyond 220 leaves the wood feeling awesome for a day, a week, maybe a month, but after that the humidity creates ridges and roughness. If I'm working quickly it's not a problem, but if I am busy with my "real job," sometimes a project can just lay there for a month and all my super high-grit sanding undoes itself.

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It also depends on what finish you're applying.  If I'm applying something that's going to build a film, I rarely sand above 180 and I block with 400 between coats.  If I'm going to apply something more natural like an oil then, I typically go to 220.  Of course end grain always goes a couple grits higher.

I typically sand much higher on the lathe and nearly always burnish the surface with sawdust before removing it from the lathe.

 

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5 hours ago, TerryMcK said:

Finish does not cover up defects it actually highlights them.

Sand bare wood to 220 and apply finish. Then lightly sand between subsequent coats with higher grits (600, 800, 1000) and after final curing 2000 to 4000. You can even use a brown grocery bag and you end up with baby butt smooth finish.

Initial sanding any higher than 220 (except on end grain which can tolerate higher grits) is a waste of energy.

Agree - great advice Terry.

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If you are building cabinets or furniture to be stained (especially dark colors) don't sand too high of a grit or you will burnish the surface and it won't take the stain well. 120 -150 grit with a ROS and then sand with the grain by hand (which will minimumize any swirl marks). After staining and a couple thin finish coats to seal sand lightly by hand with 320-400 grit between coats. Be very careful sanding near edges and corners. If you sand through the stain it can be quite difficult to touch it up.

I also sand the scraps while sanding a project, same amount of time same grits etc. Then you can test stains , seal coats and finish coats along side the project. You can feel the sample scraps for dryness and not leave fingerprints in a still wet coat. If you make a mistake like sanding through the stain repeat the error on the scraps and practice your repair before you make the error worse. Trust me you can make a small error that's bugging you into a nightmare with a clumsy repair.

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26 minutes ago, wdwerker said:

If you are building cabinets or furniture to be stained (especially dark colors) don't sand too high of a grit or you will burnish the surface and it won't take the stain well. 120 -150 grit with a ROS and then sand with the grain by hand (which will minimumize any swirl marks). After staining and a couple thin finish coats to seal sand lightly by hand with 320-400 grit between coats. Be very careful sanding near edges and corners. If you sand through the stain it can be quite difficult to touch it up.

I also sand the scraps while sanding a project, same amount of time same grits etc. Then you can test stains , seal coats and finish coats along side the project. You can feel the sample scraps for dryness and not leave fingerprints in a still wet coat. If you make a mistake like sanding through the stain repeat the error on the scraps and practice your repair before you make the error worse. Trust me you can make a small error that's bugging you into a nightmare with a clumsy repair.

I'm certain at a one time or another I've burnished the wood just as you described. Is there a standard recovery method to re-roughen the surface after it has been burnished?

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3 hours ago, Denette said:

It may just be that I'm in a very humid climate, but I find that sanding beyond 220 leaves the wood feeling awesome for a day, a week, maybe a month, but after that the humidity creates ridges and roughness.

What would happen if, before your first coat of finish, you moisten the wood surface with water to raise the grain, sand it smooth again the next day, then apply your first coat? Haven't tried this, I just recall reading about it. Mebbe try it on a similar scrap of wood to see what happens?...

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6 minutes ago, ClassAct said:

What would happen if, before your first coat of finish, you moisten the wood surface with water to raise the grain, sand it smooth again the next day, then apply your first coat? Haven't tried this, I just recall reading about it. Mebbe try it on a similar scrap of wood to see what happens?...

I believe Marc has, in one of his free videos, a section where he uses his HVLP to spray a mist on a project to raise the grain and then sand it down before finish.

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