Finish Sanding - How Fine is Fine Enough ?

[Owego]

Building a pair of end tables - curly maple.  Have all pieces currently sanded to 220 (rubin paper, RS 2E).  Finish will be lacquer, clear (maybe satin). 

As sanded (bare wood), with 220, looks and feels pretty good to me.  Will I get much of an improvement with finer grit(s) ?  If so, what is practical limit, there are four more finer grits in the Granat line, 240 up to 400.  Will finer finish be noticeable after applying 3 coats of lacquer ?  Is it necessary to step through each grade ? 

Tom

 

[mouppe]

My opinion is you don't need to sand the bare wood higher than 220. In fact, it could make the finish worse if you do because the surface will lack "tooth." Higher grits are used for sanding the finish itself, whether it be lacquer, poly, shellac etc.

 

[tjbnwi]

Look at the piece at angles with raking light. If there are no sanding marks, finish the piece. It is rare I sand past 180 on bare wood.

Tom

 

[WarnerConstCo.]

I use a scraper on curly maple.

 

[Holmz]

My first thought was 240, as 120 clearly leaves swirls.

I use a scraper on curly maple.

^Good point^ - The scraper is really optimal on hard wood.

 

[AlexThePalex]

As sanded (bare wood), with 220, looks and feels pretty good to me.  Will I get much of an improvement with finer grit(s) ?  If so, what is practical limit, there are four more finer grits in the Granat line, 240 up to 400.  Will finer finish be noticeable after applying 3 coats of lacquer ?  Is it necessary to step through each grade ? 

With laquer there isn't really an upper limit of grit you can use. The finer the grit the smoother the surface becomes. Laquer is a layer of paint that lies on top of the surface. Whether you actually see any difference if you go beyond 320-400 is in the eye of the beholder.

If you would apply other finishes like stain, it is better not to go beyond the 180-240 range because you might close of the pores of the wood, and a stain needs that because it is pulled into the wood instead of laying on top of it.

How you apply the laquer is also of matter, if you spray it, you can get a very smooth mirror like surface, and very fine sanding can help there. But if you brush it or use a roller, you leave a texture in the laquer itself, and then sanding to a very high grit has less effect.

In my father's spray shop we sprayed a lot of furniture with paint and laquer, and mostly sanded no further than 240. Only for high end specialty items did we sometimes go to 320 or beyond.

 

[Birdhunter]

I am an avid amateur so if I'm telling you something you already know, please excuse me.

When I started building projects and finishing them, I'd sand until the surface looked smooth, usually 220 grit. I'd put the first coat of, say, varnish, and see areas that needed more sanding, snipe marks, squeeze-out glue, etc. frustrating!

I'd then have to sand out these hidden flaws and remove the finish I'd just applied.

I learned to wipe the piece with mineral spirits or water to precheck for flaws before applying the first coat. I also learned to only sand to 180 if the wood was fibrous as the first finish application would raise the fibers. I'd let it dry and then sand down to 320 grit. Sanding to 320 and then applying the first coat was a complete waste of time.

 

[Scott B.]

Generally 150-180 is far enough on raw wood for most applications. Then, you always go up in steps between each coat of finish. For every coat, another step until you are satisfied with the look and feel.

It can be a mistake to go too far on the initial raw wood sanding. The "tooth" factor (mentioned by someone else in this thread), referring to adhesion of the initial coat.

The smoothness you end up with is a result of the in between coat sanding on the finish. I do think it is important on the final sand of the raw wood to do a careful inspection (as Tom mentioned) with inspection lighting and even a damp rag wipe to expose any sanding imperfection. Your eye for all of this develops the more you do it.

 

[rst]

I started my work life in a custom kitchen factory.  Bare wood sanding on every thing from pine to maple stopped at 150.  Sanding sealer was done at 220.  First coat of laquer was 320.  Second coat was 400, then steel wool with oil (it was 1970), water now days depending on type finish.  I now use fine conditionings pads, buff with Johnson's paste wax and extra fine conditioning pads.

 

[jbasen]

I go to 220 for my furniture.  One trick I learned was to go one step finer on end grain.  Going one step finer cuts down on the absorption on the end grain which naturally pulls in more stain and becomes darker than the rest of the piece.

When building furniture I do extensive dry fitting of my pieces.  Then I finish all my pieces before doing my glue-up.  I am very careful to mask all gluing surfaces so the finish doesn't affect the holding power of the glue.  Once everything is finished and dry I do my final assembly and glue-up. 

I know this probably wouldn't work for everyone but, for me, it solves a few problems

1) I never have light spots in the stain because of glue squeeze out that I missed
2) I get perfectly even staining in all the corners
3) Easier to control drips when spraying lacquer
4) Easier to get even covering of the entire piece when spraying lacquer.

It takes more time but, as a hobbyist, that isn't a big concern to me.

One other thing.  I work primarily with QSWO and part of my finish is using water based dyes.  Unfortunately the water will raise the grain on the QSWO.  So, I sand to 220, wipe the wood down with distilled water, and resand again with 220.  It is important to use distilled water as iron in the water can react with the tannin in the wood and cause problems.

Hope this helps

 

[Cheese]

One trick I learned was to go one step finer on end grain.  Going one step finer cuts down on the absorption on the end grain which naturally pulls in more stain and becomes darker than the rest of the piece.

Good tip...that's one I'll use. [thumbs up] I may even try 2 steps finer and see how that looks.