Sanding question.

[JJ1]

I've just read a short article and it states that sanding hardwoods beyond 220 grit offers little benefit and 180 grit is the sweet spot if intending to stain the wood.
I was wondering if this also applies when using an oil finish. The reason I ask is I'm sure I've heard others mention sanding with 400, and even 600 grit prior to finishing.
As an example, I've just finished sanding an Ercol elm coffee table top prior to finishing with Danish Oil and I wondered what other forum members would have sanded the top to.

Any advice/opinions would be much appreciated, thanks.

 

[Peter Sefton]

I assume your Ercol is Elm, for an open grained ring pours timber like this I would say sanding with 180 grit with the grain is plenty high enough. If you were sanding a finer timber or end grain you may go higher.

If you over sand you can burnish the timber and stain or finish may not grab, and delaminate later.

Cheers Peter

 

[CHJ]

Very rarely do I sand my turnings below 240 grit, and as Peter says as long as you sand with the grain very few woods show any sanding blemishes.
If going for a gloss finish it is the polymerised oil or sanding sealer skin that takes the gloss polishing, not the wood base on the pieces I make.

 

[JJ1]

Thanks very much for your help

 

[rafezetter]

I assume your Ercol is Elm, for an open grained ring pours timber like this I would say sanding with 180 grit with the grain is plenty high enough. If you were sanding a finer timber or end grain you may go higher.

If you over sand you can burnish the timber and stain or finish may not grab, and delaminate later.

Cheers Peter

This^^^

Oak, ash, elm, walnut, chestnut and the like don't need anything above 180grit - or should I say will not gain anything from going higher. A simple rule of thumb is if you can see the open grain pores, 180grit is high enough. 240grit+ is only really needed on tight, closed grain woods like maple, beech, birch etc etc.

However, the point about burnishing is well made - consider that most surface finishes; laquers, shellac, varnishes; require a surface "key" to have something to hold on to - if you go too high and the wood starts to become glossy and polished on it's own it would have the effect of putting varnish on glass, it'll stick for a while, but won't properly bond and it'll just delam later on as Peter said.

 

[JJ1]

That's superb advice and giving an indication of which species benefit from a slightly higher grit is very useful indeed. Many thanks


One other issue that comes to mind, is, Ive been reading up about using scrapers and smoothing planes and I've heard it said by many that the surface from a scraper and/or smoothing plane is often preferred to an abraded surface from sanding. How do you deal with finishing a surface in that instance? I'm assuming a well-planed or scraped surface would be similar in smoothness to a very high grit abrasive and may, in that situation, be too smooth to successfully apply a finish to, or is that not the case. Any thoughts or opinions on that particular scenario?

 

[mouppe]

That's superb advice and giving an indication of which species benefit from a slightly higher grit is very useful indeed. Many thanks


One other issue that comes to mind, is, Ive been reading up about using scrapers and smoothing planes and I've heard it said by many that the surface from a scraper and/or smoothing plane is often preferred to an abraded surface from sanding. How do you deal with finishing a surface in that instance? I'm assuming a well-planed or scraped surface would be similar in smoothness to a very high grit abrasive and may, in that situation, be too smooth to successfully apply a finish to, or is that not the case. Any thoughts or opinions on that particular scenario?

Yes, sometimes the surface left by a smoothing plane is so smooth that it needs to be passed over with a fine sandpaper so it can take a finish. Depends on the finish too of course.

Sanding also raises the grain more than a planed surface.

 

[Peter Sefton]

The finish and smoothness that can be achieve from a well tuned planed is fantastic on a drawer front for instance. But furniture is made of many shaped and varying surfaces coming together with different grain directions and shapes. The idea of finishing straight from the plane or scraper is in my opinion romantic and totally out of kilter with commercial furniture making.

Sanding with abrasive papers or Abranet prior to finishing will give a far more consistent surface. When applying a finish across the various materials being prepared including solid and veneered work both flat curved and moulded (in solid work). It should also give confidence that no wax or other deposits from the planes sole are left on the pretreated surface prior to finishing or staining were all problems then become apparent.

Sanding in it's self is a very important technique to master and I have seen many a great piece of work spoilt by either poor or a lack of enough sanding. Leaving either machine scoops, pencil lines or tool marks left in for history to judge.

Cheers Peter

 

[YoungSalt]

When talking varnish, I would sand to 180-220 (maximum 220, but it depends on the timber) before varnishing, but then work up between coats to 320, 400 before the final coat...don't know if that really answers your question though!

 

[JJ1]

Thanks again for the excellent advice and the advice to finish with Abranet suits me just fine as I'm a lot more comfortable with that than I am with my fairly limited smoothing plane skills