shellac finish?

[sunnybob]

I'm getting quite adventursome now, I've just made a garden coffee table that actually has JOINTS in the base :shock: :shock:
(its a garden table because those joints would not be allowed inside, but hey, they're better than the last ones I made when I was 12))
But I am not getting a good finish with the (new to me) shellac.
The edge of the top is in maple. I sand it smooth to 320 grit, and brush on thin shellac. the first coat dries almost at once.
The second coat takes a little longer.
But once dry, the maple now feels like I sanded with 80 grit?
So I sand that surface down to 400 grit and apply another coat.
When its wet it gleams, but when it dries it STILL dries like 80 grit.
What am I doing wrong please?

 

[CHJ]

Are you wiping the sanded surface down with a tack cloth to remove dust debris?

(Or wet wipe with spirits if you don't have tack cloth)

 

[profchris]

That's what I get with shellac too, though I wipe on thin coats. I think it raises the grain slightly, and because the coat is so thin it feels rough.

If you sand back thoroughly you expose more wood fibres, so you're nearly back to stage 1.

What I do is to sand back to smooth after coat 1, sand back less aggressively after coat 2, and thereafter I do little more than dust the surface with my fine abrasive, just enough to remove any roughness. After about coat 4 or 5 all is smooth.

Shellac goes on in really thin coats so you need lots of them - on a ukulele I might apply a dozen wiped on coats in total and get a film thickness that's maybe as thick as a sheet of copier paper, maybe even less. But they go on and dry really fast - on a UK summer's day I might apply 6 coats, in Cyprus you might apply all 12!

A thicker cut builds faster but dries a lot slower, and if you apply the next coat before the previous is fully dry you can get problems, with the finish producing sticky patches and distortions. Lots of thin coats is what works for me, and it's pretty much foolproof.

So it's both slow and quick, paradoxically. I'd guess brushing one thin coat onto a coffee table top takes 2 or 3 minutes, and then the same to dust it with abrasive once it's dry. So 72 minutes to apply 12 coats, but spread over 2 or 3 days.

 

[Rorschach]

I tend to do a few coats and then knock it back with at least 320, usually higher. You don't want to sand through the shellac, just take off the roughness, it might take two or 3 light strokes at most, then add a couple more coats of shellac. You don't need to worry about providing a key for the shellac, just making it smooth.

 

[sunnybob]

I use a soft brush to remove dust before applying the shellac. Never actually seen a tack cloth.
When i start sanding again I start with 220, then 320, then 400.

I've gone up to 5 coats before and still dont get a really smooth finish. maybe i should try some 0000 wool?

 

[xy mosian]

Did you raise the grain, with water, and sand again, when dry, before applying any finish?
xy

 

[sunnybob]

No.
But I have sanded the shellac surface three times if that helps :roll: :roll:

 

[profchris]

I reckon 5 coats is not even half way! If you scraped back to bare wood in one spot you'd see how thin the film is.

 

[profchris]

This what a dozen coats looks like - you can get shinier with a few more and then buffing with rubbing compound.

 

[sunnybob]

Define rubbing compound?
I have metal polishing compound in three different grades.

 

[profchris]

I use T-Cut automotive rubbing compound. I reckon metal polish would work well.

But leave it a couple of weeks to harden before you go down that route. I wet sand *very lightly* with P1,000 wet and dry, then the rubbing compound. Or sometimes I leave out the wet sanding. If you have no pores, or have pore filled, you can get a mirror finish by going increasingly fine with the rubbing compound. I stop when it's shiny enough for a musician

Don't forget it's a thin film, so don't go too wild!

 

[profchris]

Oh, one more thing - an outside coffee table? Shellac is rather fragile for that - UK rain won't do it any good (but you're in Cyprus I think, maybe your rain is OK), and coffee mugs leave rings. And it's alcohol soluble, so wine and beer glasses are a danger. OTOH it's easy to repair.

 

[sunnybob]

I was concerned metal polishing compounds would blacken the wood, I'll have to try it on a scrap piece.
Its a one piece ceramic tile top, with maple edging, on a frame of ... emmm, construction timber :roll:
This is a learning exercise so I wasnt prepared to spend money on good quality hardwood that could so easily have gone straight to the scrap bin.
But it is under cover so rain should not be an issue (it will be raised off the floor for monsoon season)

I'll take all this under advisement for future projects where a gloss finish would be more appropriate.
Thanks all. =D> =D> =D>

 

[xy mosian]

No.
But I have sanded the shellac surface three times if that helps :roll: :roll:

I cannot answer that as I always raise the grain, with water, before applying a Shellac finish. That goes for many other finishes as well.
I suspect that raising the grain before hand might well have significantly reduced the snags you have come across.
xy

 

[sunnybob]

I'll try that on the next table, thanks

 

[xy mosian]

I'll try that on the next table, thanks

I think you will find it very useful. There will be more experienced than me around these parts, they may have comments. Meanwhile I found this:

https://www.highlandwoodworking.com/rai ... osand.aspx

Be careful if your table happens to be veneered.

xy