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What finish for a Koa table top?

Roger99's picture

Hi all; I am making two end tables. They are Craftsman style mahogany wood frames with Koa board tops. The frame is finished in shellac and looks great. What finish should I use for the tops to both bring out the figure of Koa and protect it? I was thinking of using oil based poly on the table tops. Because it is oil based it does pop the grain, but I have never used Koa before. I am going to try different finished on a scrap, but still need advice. Thanks, Roger  rsolheid@sbcglobal.net


Edited 8/15/2006 11:58 am ET by Roger99

SteveSchoene's picture

(post #110639, reply #1 of 8)

I would not use a polyurethane varnish.  You don't need the special properties of poly since I doubt you will walk on the tables.  An traditional resin varnish will be essentially as durable as poly in that application. 


Personally, I would use shellac on the tops just as on the frames.  Looks great, as you see already, and will match nicely.  Shellac requires a little care, but is generally quite durable.  There are no polyurethane finishes that have passed the test of lasting for 75 years, but lots of shellac finishes have survived several times that long while looking well.  


(Yeah, I know poly hasn't been around 75 years)  But, in general, general environmental factors will damage shellac less than most finishes.  It's the old varnish and oil finishes that have turned antiques black and dingy.    

Test your finish on scrap, FIRST, or risk having to scrap your finish.

Kaleo's picture

(post #110639, reply #2 of 8)

I would use a straight oil finish. I know that alot of people don't likke to use just oil, because it takes a long time to do. Meaning that you have to apply a lot of coats to it, and there is usually about a 12 to 24 hour dry time inbetween coats. But nothing beats the look. I've used oil on a chair that I just made, I made it out of tasmanian blackkwood, which is in the same family as Koa. Also originally being from Hawaii, Koa is way to beautiful to put a Polyurethane on.

Kaleo

www.kalafinefurniture.blogspot.com

SteveSchoene's picture

(post #110639, reply #6 of 8)

A straight oil finish adds virtually no protection.  Cold glasses will leave rings--in the wood not just the finish.  Shellac is much better in that respect.  If you want an "oil finish" I recommend an oil/varnish blend such as Watco.  As far as appearance goes it will be extremely difficult to tell oil/varnish from oil, but the protection, while not great, will be quite a bit better than oil alone. 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

Kaleo's picture

(post #110639, reply #7 of 8)

That's not absolutly true. If you add enough coats of oil you won't get rings from hot or cold drinks. It's just that people don't want to take the time to do it. I have a coffee table that I made over 5 years ago with nothing but an oil finish and have never had a ring from anything. Oil and Shellac kare the only 2 finishes that I use. But I use Oil most of the time.

Kaleo

SteveSchoene's picture

(post #110639, reply #8 of 8)

Tung oil might get a little bit of water protection after many coats, BLO still builds to almost no protection.  But why mess with pure oil when the oil/varnish will look virtually identical, but clearly perform better.  But either oil/varnish or oil is irrelevant in this context since the poster had already used shellac on the frame or base.  Since he already has a film finish on part, a film finish makes sense for the top. 


I don't get water rings either, but I use coasters.  Frankly, I don't understand the aversion to coasters, or otherwise taking care of things.  Sure it is possible to avoid damaging oil finishes, but the poster didn't want to be careful.  If you don't want to be careful a varnish is the only way to go--just not polyurethane varnish. 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

ring's picture

(post #110639, reply #3 of 8)

I have to agree with the oil finish.  My son has a coffee table made with an 8' koa slab, finish is many coats of danish oil.  It's still beautiful after about 5 years of use.


DR

Elcoholic's picture

(post #110639, reply #4 of 8)

When I built my 8' (2 board top) KOA dining room table I was looking for durability so that we could use it everyday without ever having to worry about a glass or a spill.  I wanted to be able to enjoy the meals with family & friends, not play coaster police or hide it under pads or table cloths.  I did some experimentation and settled on BLO followed by a sprayed, dewaxed shellac barrier coat, leveled, and top-coated with sprayed Enduro Poly W/B which I tinted.  2 light coats rubbed out gives a lot of protection without it looking plastic coated. The only thing I have to worry about are trivets for hot dishes.  Granted Koa looks best with just oil, but I chose not to try to live with a gallery piece.  Besides I had a lot of tinted epoxy filled bark inclusions that oil wouldn't work on anyway.  End tables don't see the same use as dining tables, but mine see a lot of sweaty beer bottles, wine glasses, etc.  They're made out of some exquisite air-dried old growth walnut and are sprayed with EnduroPoly (Amber Overprint) too.


John O'Connell - JKO Handcrafted Woodworking


The more things change ...


We trained hard, but it seemed that every time we were beginning to form up into teams, we would be reorganized.  I was to learn later in life that we tend to meet any new situation by reorganizing; and a wonderful method it can be for creating the illusion of progress while producing confusion, inefficiency, and demoralization.


Petronious Arbiter, 210 BC

John O'Connell - JKO Handcrafted Woodworking

The more things change ...

We trained hard, but it seemed that every time we were beginning to form up into teams, we would be reorganized.  I was to learn later in life that we tend to meet any new situation by reorganizing; and a wonderful method it can be for creating the illusion of progress while producing confusion, inefficiency, and demoralization.

Petronious Arbiter, 210 BC

sapwood's picture

(post #110639, reply #5 of 8)

Oil, your choice of brand. So it might not be as durable as poly. So what? It will gain a patina. Just like you. Aging is natural and grand.