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Does sanding go more quickly as you move up the grits?

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Forum topic by HarveyDunn posted 12-05-2020 12:43 PM 434 views 0 times favorited 4 replies Add to Favorites Watch
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HarveyDunn

417 posts in 2700 days


12-05-2020 12:43 PM

I’m sanding poplar and pine boards to 320 with a ROS, using the pencil trick: marking numerous light lines/squiggles before each grit, so that I know I’m not “done” until every bit of it is gone.

It seems to go more quickly with each higher grit. Is that just because the graphite doesn’t penetrate as deep in the smoother surfaces? Or is it a real phenomenon?

How does the pencil trick compare to “trace coating”.

Any other advice? I’m relatively new to this and would like to execute it well & efficiently.

My finish will be dye and then shellac.


4 replies so far

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EarlS

4208 posts in 3317 days


#1 posted 12-05-2020 12:57 PM

As the grits get finer, so do the scratches they leave in the wood. That also means the depth of the scratches decreases. You have to take off less material to remove a shallow scratch. Since the graphite fills the scratches, there is less of it in a shallow scratch

I tend to look at the sanded surface with a strong light at an angle to make sure I’ve gotten out all of the coarse scratches. Sometimes I will also wet the surface, which also helps raise the grain.

I use the pencil trick if there are high/low place, or where boards are glued together. Seems like there is always one or two spots that show up when stain or finish is is applied.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

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HarveyDunn

417 posts in 2700 days


#2 posted 12-05-2020 01:43 PM

Do you raise the grain with each new grit?

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Madmark2

2056 posts in 1557 days


#3 posted 12-05-2020 03:08 PM

Don’t bother sanding poplar or pine past the 180-220 range. The wood won’t go higher. Only really hard hardwoods need higher grits.

Poplar is generally considered “paint grade” because of its crappy color over time. Those lovely green flashes in poplar will eventually turn an ugly tannish brown.

You should be able to feel when the grit stops cutting. I make even “out and back” passes with the ROS, counting as I go. Usually around the 6th or 8th “out and back” I feel the ROS get … lighter … on the the wood.

Do your grit steps about 1/2 more than the last pass. Say: 80, 120, 180. No need to hit every grit in between.

-- The hump with the stump and the pump!

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CaptainKlutz

3991 posts in 2463 days


#4 posted 12-05-2020 03:19 PM

Sounds like too much sanding to me?

- Try using side light and looking at your scratch patterns.
When scratches disappear from last grit, time to stop and move to next grit.

- I almost never sand past 180grit when adding color to wood.
If you polish the surface with fine grit 220+, it absorbs less color. Less color is ok, if that is intended purpose? Finely polished wood is very hard to make a dark color.

- Beware of over sanding, especially on softwood like pine.
There is large difference in hardness between early and late wood in softwood grain. If you sand too much, the surface will be smooth to the touch, but will not be flat due difference in hardness and slight give on the ROS pad.

You sure do ask a lot of finishing questions. Maybe you need a good book or two on subject?

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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