Birch plywood finishing

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
How do you finish good quality plywood?

Using russian birch ply I've sanded down with 180 grit and applied danish oil which results in a blotchy finish. Trying it over an undiluted pva base makes the finish even but with a bad surface finish.

Is the best method to apply many diluted pva/water coats and sand down each coat etc. before applying any oils/waxes?

Please share your favourite method of finishing ply to give me some inspiration! ;)

The 1/4 slice is the one applied over the PVA.
 

Attachments

  • dsc03390.jpg
    dsc03390.jpg
    95.3 KB · Views: 3,542
Don't like the 1/4" slice...

What's wrong with tht 3/4" slice? Looks gorgeous though just like that!

The blotchiness you describe may be tearing in the grain. Plywoods are prone to this because they are peeled and not oringinally flat. I suspect this because the light spots do seem to follow a certain alignment in the grain.

Try sanding with 320 or finer... birch is hard as hell and will reward your results.

Not that I couln't learn something new... but what is up with using PVA as a finish? That's a new one on me. Curious, but I don't think I would mix it with oil.

Are you going for a blonde finish?

:)
 
In most cases you shouldn't really sand plywood because
it's just a thin veneer of the quality wood on the outside.
Lightly sand with a few strokes if anything.

Please share your favourite method of finishing ply to give me some inspiration!

There are a zillion recipes for wood finishing, I've tried many.
Sometimes the simple recipe works best like applying some
stain, let dry then apply a thin coat or two of polyurethane by
spray or wipe on method.
 
The blotchiness is caused by the same effect as solid wood: differences in grain absorbing the colour coat to a varying degree. IME, the fix is the same as with solid wood: apply a sanding sealer as a first layer before you apply your colour/finishing layer. With birch ply, I've done sanding sealer + natural colour stain + polyurethane protective coat and was very happy with it. I use MinWax products because they are cheap at Wal-Mart.
 
Looks familiar!

What you are probably seeing is the oil accentuating the natural characteristics of the wood. Oil is noted for this effect.
Birch can be unruly. Especialy radialy cut or "peeled" veneer as in your example.

If what you have is not appealing try a surface finish like lacquer or water white varnish. Water borne varnishes/poly's and most lacquers will do less to accentuate the wildness of the grain pattern.
Avoid finishes with high oil content or that appear amber in the can.
Most water borne varnishes fit the bill perfectly.

You could also try sanding sealer as a first coat. It has a high stearate content that fills and blocks the grain somewhat for a more even finish. Follow with lacquer as a top coat.

An oil based pigmented stain, not dye, that is nearly the same color as the darker portions of the raw wood can even the tone some too. But it will make for a darker finish.
Don't use Minwax stain, too much dye in it. Use varnish as a top coat.

A coat of very dilute blonde or bleached shellac* may be necesary before the varnish if the wood is very ill behaved.
You can try the dilute shellac before the stain too if the stain appears too uneven.

*Very dilute is like 4 to 6 parts alcohol to 1 part pre-mixed blonde or bleached shellac. Or 1-3 teaspoons of flakes in a pint of alcohol. You'll know it's right if it seems too thin at first, as though nothing is there, but it works wonders.
 
I'll pick up some sanding sealer and see how that goes.

On the pic below I've tried a few coats of pva (left for 10 mins) and then a single coat of danish oil (left overnight) followed by generous amount of aerosol applied lacquer. This looks to be one way to go (but with a better base instead of pva and proper 2pk lacquer). It looks better in the pic then in the flesh.

An externally hosted image should be here but it was not working when we last tested it.
 
I wouldn't trust myself with a plane. I barely trust myself with a sander. I remember when I was building my first ever speakers at uni, I used a powered planer and ripped the MDF cab to shreads. My house mates laughed. A lot.

What wax do you use pm?

I'm looking for a light overall finish but one that still shows up the natural wood veins. I'm not after a rich/dark or amber looking finish so the danish oil will probably be dropped.

A final color something like this would be ideal (or even the table the round scrap ply is sitting on in the pic a few posts up):

kroll2.jpg
 
Ex-Moderator
Joined 2002
This is a cabinet scraper. It's a great tool for finishing, and once you get the hang of it, really nice to work with.

As for finishing, for I would guess for 90% of my projects, I use Mylands Antique Wax, it has a slight brown stain that really brings out the wood. Below you can see some samples, bottom is raw wood, middle is with the acrylic, and top is with a final coat of the above wax. Birch is quite difficult to get good grain figuring unless you use some sort of colour somewhere in the process.
 

Attachments

  • birch copy.jpg
    birch copy.jpg
    83.3 KB · Views: 2,969
Actually Vikash,

The burnisher Pinkmouse talks about is not that unwieldy of a tool. I have made some out of spent blades from block planes. And this could work wonders getting rid of your 'blotches". These are what real men used before sandaper. Finding one might be your challenge.

Seriously, try sanding, by hand, with finer grits... The reason you are seeing white areas is because the light is diffusing instead reflecting coherently. This comes from rough, splayed, stressed fibers at odd angles.

Many people are recommending oil this and oil that... even so far as to put oil between layers of polymers. This is asking for disaster. Don't get me wrong... I like oil finishes, but oil between or under laquers and poly's is asking for trouble. Especially Danish oil which contains Teak oil (wax really). It is oil after all... and the first thing you read on any paint can is: "remove all oil, wax, grease, and dirt". You don't see thes instructions on clears intended for wood... the reasons are less than honorable. Have you ever felt wood finishes that are always sticky or soft? Oil stain... with diluted polymer over it... never really dries.

I have restored the woodwork in many of the Rolls and Bentleys you chaps built. While true that these finishes see temperatures and humidities that a speaker won't; having to do that same woodwork over again because the finish peeled six months later taught me enough.



:)
 
Vikash said:
Yep, I have plenty of sanding supplies but reading up on this scraper thing has got me sold. It comes across as an almost magical thing that will leave the surface near perfect in a fraction of the time. I can't resist that as sanding is the bane of my cabinet building life.

Give Lee Valley Tools a try. Scrapers work great on solid wood, and even MDF. You will need to watch any exposed edges of plywood as they can chip out. You will never get rid of your sander, but you can certainly cut down it with a scraper.

G.
 
Ok,

I would still try sanding though... even if only on a small piece to verify that tearing is indeed the cause of the blotches.

Keep in mind, when scrapers were in their heyday, there was no such thing as peeled veneers. So, a scraper might do the trick, or it might aggravate the tearing.

Some of the tools required for scrapers have simple subs... a steel for your kitchen knives will serve as a burnisher, as well as a round screwdriver blade.

A couple coats of sanding sealer with light sanding in between might do it as well.


:xeye:
 
It's defintely tearing. I've just tried sanding with 180 grit and it doesn't get close to flattening it properly. On close inspection you can clearly see the tear outs when you move the piece around under light.

I've used Axminster before. They have the stuff, but I still don't know what I need to pick out exactly :dead:

I need someone to lend me a pre-prepared scraper, or perhaps a fine plane (hint hint).

Otherwise I'll try the sanding sealer and see if I can live with the results.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.