Saturday, July 11, 2009

Favourite Things Part 2

Finishing is a tricky subject – it can make or break a project. There are many different finishes, and almost as many different ways to apply them. After using most of the types of finish available I find myself reaching for the Shellac nine times out of ten.

So what is shellac? It is a resin excreted by the Lac bug which feeds on braches of certain trees. The resin is harvested and then purified – the different levels of purification give different shades of shellac, from dark brown through to clear. It is dissolved in alcohol (methylated spirit is fine) and by varying the amount of alcohol to shellac (or the “cut”) you can get different strength solutions (i.e. thicker for bodying up).

Shellac has some excellent traits :

  • It will bond to pretty much anything
  • It dries very fast
  • No strong smell
  • Easily removed – just wipe off with an alcohol soaked rag.
  • Each application melts into previous layers, so no problems with “sand through”
  • Most other finishes will bond to it, so it can be used as a sealer (i.e. between an oil based finish and a water based finish)

For me one of the best things about shellac is its versatility – you can wipe on a single thing coat to seal the timber against fingerprints (think Jim Krenov’s method of finishing) or you can continue to add layers of finish to get the desired sheen or thickness. And the speed with which it dries means you can make some serious progress – no waiting overnight for the finish to cure. Only a couple of minutes are needed for it to be dry.

Ease of application is another plus – I’ve used paper towels, rags, mini-rollers and brushes. You can also spray it, but I’ve never felt the need to.

So what downsides are there to shellac? Well, it is dissolved in alcohol, so shellac probably wouldn’t make the best finish for a bar top – a few splashed drops of whiskey would spell disaster. Its also not water proof, so is only suitable for indoor use. But that’s about it.

Shellac is a wonderful finish for wood – it brings out the beauty of the grain and figure and makes it shine. It is a natural finish that has been used for centuries and just looks “right”. My favourite technique is to apply a coat of oil to the piece, buff it dry and then apply shellac. This gives a deep shine and makes the figuring jump out at you. And its quick and easy to do!

One final comment – there are many different shades of shellac. Experiment with them on different colour timbers – I love garnet on walnut, and lemon adds an interesting “vintage” tint to most timbers.


Auguste Gusteau said...

If you want to add a good aroma to your shellac try to mix it with some Benzoin resin.
It will improve the elastic properties of the shellac and give to you works a special touch.

Ron Hock said...

Hi Philly,

I couldn't agree more about shellac's versatility, repair-ability, etc. Great stuff! (And one of very few insect products that we use.) As to the bar-top, you're right, but I tested it with wine, which dried without a trace, and vodka, which also dried with just a hint of gloss removal. But when a glass is left in a puddle of vodka, it softened enough overnight to leave an indented ring in the shellac. So, clean up after the party and you should be good for the next morning (hangovers notwithstanding.)

As to water resistance, freshly mixed shellac is very water resistant (billions of lac bugs can't be wrong). I tested a sample by leaving it outside for an entire rainy February with no damage to the finish at all. (I had covered half the sample with foil to compare.) Shellac begins to degrade as soon as it's mixed and with time will not dry quickly or at all. Also, with time, its water resistance is reduced which is why so many people think it is not very waterproof. Fresh shellac is the answer to many problems.

The problem I've found with shellac is its low melting point. A nice hot cuppa will leave an unsightly ring sure as heck. So, unless you want to end up like your a aunt, always rushing in with a coaster, I don't recommend shellac for a tea tray, etc.

Keep up the good work!


The Village Carpenter said...

Phil, shellac is one of my favorite finishes, too. I've never applied it over top of oil, though. How long do you wait for the oil to dry before shellacing? A week?

One time, I used shellac that had gone bad (never dry) and it was a blessing that it could be removed so easily with alcohol.

Philly said...

Auguste- might try that, thanks!

That makes a lot of sense to me - we take so many aspects of woodwork for granted, assuming that what we read is correct. You really have to experiment to find out the truth - just because something has "always been done this way" doesn't mean its the most efficient way (or correct!!)
I'll make sure I keep my cuppa somewhere safe - like in my hand :)

I have wiped the shellac on immediately with no problems. I usually give it ten minutes though, to make sure its well absorbed.
Its pretty easy to tell when shellac is off - fresh stuff sets almost immediately.
Best regards

Woodbloke said...

Hi Philly - shellac does it for me as well. I've used the oil technique as well on several projects but I generally leave it overnight to dry completely before I attack with the shellac. The handles of the 'Blokeblades' are now done with shellac and it takes me from about T to bed time to get enough coats on to get a decent depth of finish...and I always leave overnight with that much polish on the wood to fully cure. Good stuff! - Rob