Finishing burr walnut

[Woodmonkey]

I'm in the process of making a sideboard with a veneered top in burr walnut. My go-to finish for table tops is osmo oil, mainly as i like the hard wearing matt finish it gives and ease of use, but I do think it can look a little flat and really want something that will pop the grain of the walnut, any suggestions? Should I fill the grain with something first?
I don't have any spraying gear.

 

[custard]

That's a big question Woodmonkey. Where are you with laying the actual veneer?

 

[ED65]

Burrs were very commonly oiled to make the most of their grain so that's how I'd start. This is with a plain oil, mostly some type of linseed in the past in our part of the world, not a blended oil finish like the Osmo but I don't see any reason this wouldn't pop the grain just as well as a straight oil. It's mostly the matt finish that would lessen the effect, same as a matt finish makes any wood look a little flatter or duller.

You can continue oiling if you want a straight oil finish which can be quite durable if you build it up, and it's possible to achieve a pretty good gloss on harder woods, if you're willing to take the time to do it right. Figure it'll take at least a couple of weeks, longer if your workshop is cold and you have to wait longer between coats. I wouldn't bother myself, I'd oil to pop the grain and then switch to wiping on varnish immediately. This will give you the same gloss as many applications of oil in a fraction of the time (two or three days), with far less sweat expended and giving better resistance to scratches and water.

Although it is good practice to grain fill with an oil finish whether to fill grain is largely a matter of taste. On furniture pieces I don't care for voids showing, but obviously other people don't mind it. If you want the surface gloss uninterrupted by little dark specs then yes, fill.

 

[Woodmonkey]

Custard - I have stuck the veneer to the substrate but haven't starting cleaning it up yet
ED65 - varnish on top of oil? What kind of oil/ varnish? My workshop is cold, and I'm not in there every day so don't really want something too convoluted

 

[custard]

IIRC you veneer with PVA or UF in a vac bag? If that's the process you followed here with a fissured and fractured burr veneer then the show face is likely to be heavily impregnated with glue as the vacuum will have pulled it through from the substrate.

This sounds like a substantial and important project, so I guess you really don't want to screw it up. Therefore you might want to quickly re-veneer a bit of MDF with an off-cut from your burr, that'll give you a test piece to work on.

Personally, if spraying (or subbing the job out for spraying) is off the table I'd grain fill with a tinted oil based filler then go straight to a quality varnish. Varnishing is a traditional finish for European Walnut and very lovely it looks too, the warmth of the varnish counters the cool tones you normally find in Walnut.

 

[Woodmonkey]

Yes uf glue in a bag press, I put some brown umber pigment in the glue so at least the bleed through is walnut coloured. The test piece is a good idea, I will do that.
Can you recommend any particular varnish, there are a lot to choose from...

 

[custard]

Can you recommend any particular varnish, there are a lot to choose from...

It depends what your priorities are, UV protection, ease of application, level of gloss, spill resistance, etc etc.

If you want a straightforward, great quality product with good technical support you could try the Epifanes range,

https://www.epifanes.com/page/clear-finishes

Or alternatively, if you fancy a bit of alchemy but don't want the hassle of brewing your own then you could go for something exotic like a violin makers traditional oil varnish,

http://www.hammerl.com/english/index.php

Incidentally, if you're going to grain fill first you'll need an oil based product.

Test the entire finishing regime first on some scrap.

Good luck!

 

[Woodmonkey]

Many thanks, have ordered a tin of epifanes, will see how I get on with that.

 

[ED65]

ED65 - varnish on top of oil?

Yep. New to you? This is extremely common now in case you've never come across it before, and of course historically woods were frequently oiled to enhance chatoyance and increase contrast prior to French polishing.

My workshop is cold, and I'm not in there every day so don't really want something too convoluted

You'd only be looking at a labour-intensive and long process if you were doing an oil-only finish where you have to do the usual apply oil, wipe away all the excess, buff, wait, repeat for as many days as your patience holds out.

If you're planning on varnishing as your topcoat you just need to oil once, and it can be as thin as anything and you'll still get the effect.

The oil type doesn't matter a great deal, as long as it's a drying oil of course. But the colour of it isn't a big factor. On a darker wood you get much the same reaction from walnut oil (very pale) as you do from a typical BLO which is usually that amber/tan colour we're all familiar with.

Varnish type? Whatever you're comfortable with already would have been my recommendation so you know what it does and how it behaves. All you need to do is thin it some to make it into a wiping varnish and start applying your coats, as many as you like. Three is the minimum I'd use, really no upper limit within reason.

 

[custard]

The issue isn't varnish on top of oil. The issue is finishing on top of UF glue!

Smart move tinting the adhesive, but with an extended setting time, a porous veneer, and an unheated vac bag that's still not a guaranteed success. If you're heavily invested in this project then test on similarly veneered scrap to prove a finishing regime.