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Help sanding between coats of poly

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Forum topic by yellowtruck75 posted 01-25-2012 03:13 AM 4716 views 0 times favorited 9 replies Add to Favorites Watch
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yellowtruck75

418 posts in 1754 days


01-25-2012 03:13 AM

The first coat of poly is dry on the red oak table that I am building and I need to sand before the next coat to remove any dust particles. I have never sanded between coats of finish before and it makes me nervous. Do I use 400 grit paper and can I use my Dewalt ROS to sand? What do I do after sanding to clean the surface for the next coat?

Thanks


9 replies so far

View JAAune's profile

JAAune

868 posts in 1003 days


#1 posted 01-25-2012 03:43 AM

I would avoid using power sanders unless the surface is large and flat and you are very confident with your ability to control the machine. It’s seldom worth the risk of burn through.

400 grit works fine but be sure to sand with the grain. My preference is 600 grit for scuff-sanding between coats.

A lint free rag lightly dampened with mineral spirits is one way to remove the dust.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View Clint Searl's profile

Clint Searl

1474 posts in 1048 days


#2 posted 01-25-2012 04:04 AM

You don’t need to sand unless you left streaky brush work, in wich case sanding back to bare wood is in order. The first coat is best applied as a thinned wipe-on. When it’s dry, the inevitable fuzz and nubs can be knocked down with maroon scotchbrite, folluwed by a wet dusting with naptha, Follow-on coats don’t need sanding in between. The final coat can be rubbed out or not, depending on the look you want

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

View Loren's profile (online now)

Loren

7732 posts in 2335 days


#3 posted 01-25-2012 04:44 AM

I usually hand sand poly between coats with 320 grit folded
stearated paper.

-- http://lawoodworking.com

View Howie's profile

Howie

2656 posts in 1610 days


#4 posted 01-25-2012 05:09 AM

I’m with Loren. Hand sand lightly with 320.

-- Life is good.

View IrreverentJack's profile

IrreverentJack

724 posts in 1530 days


#5 posted 01-25-2012 04:57 PM

I like to use a cabinet scraper (very lightly) to take off the dust and any high spots, then the 320 paper. -Jack

View Bill White's profile

Bill White

3496 posts in 2647 days


#6 posted 01-25-2012 05:27 PM

I’ve started using the synthetic pads. They won’t level a surface, but sure do a good job of scuffing between coats. Just a thought.
Bill

-- bill@magraphics.us

View bobsmyuncle's profile

bobsmyuncle

110 posts in 1378 days


#7 posted 01-25-2012 05:43 PM

When using poly, I think it’s important to sand between every coat for two reasons:
- Poly lacks the chemical “burn in” that adheres multiple layers into one. That is, while multiple applications of lacquer or shellac become “one layer”, multiple applications of poly become multiple layers. So it helps to have a bit of roughness for mechanical bite.

- Poly is very slow drying comparatively speaking. While it dries, anything landing in there from the air becomes embedded dust nibs.

I sand first with P400 paper. I like 3M’s 216u. At about a buck a sheet, it’s relatively expensive, but it goes a long way without clogging (assuming you let the poly dry enough). This gets out the big defects.

Then I use light gray non-woven abrasive (Scotch-Brite / Norton / Mirka) to overall dull the surface.

You are not trying to remove a lot of finish – just the defects and provide an overall dull surface. I would not use a power sander. It’s too easy to cut through the finish, especially on the edges where it’s thinner.

When I teach finishing, I tell students the two most common defects in poly finishes (the ones that make it look “plastic’) are
- Putting on too thick layers. Thin the poly and put on as little as possible to provide even coverage. Then “tip off”.

- Not sanding between coats.

View ChuckC's profile

ChuckC

697 posts in 1622 days


#8 posted 01-25-2012 06:06 PM

I sand by hand with a 320 foam sanding block between coats, cleaning with mineral spirits. The last coat gets anywhere from 600 to 1200, also by hand. Wax after that.

View cdarney's profile

cdarney

77 posts in 1717 days


#9 posted 01-25-2012 09:36 PM

I like to put on one or two coats of wipe-on poly then sand lightly – just knock the “shiny” off – with used 220 grit or 320 grit. I usually save my used 220 pads just for this purpose. After that I wipe off well with a tack cloth I put another very light coat or two of wipe-on. Depending on the piece, wax follows.

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