Monday, 18 July 2011

Red Wooden Heart - Mixing the Shellac for French Polishing

Today I'll describe how to mix the sanding sealer and french polish for our pretty red heart.  You'll need:
Blonde dewaxed shellac, Powdered wood dye and a tack cloth.

A note about Shellac: I chose the blonde dewaxed variety as it is well known for drying clear – I wanted to have a good clear base for mixing the dye, without tints of brown etc.

A note about methylated spirit – in the UK, meths is dyed purple, which can affect the final colour of your polish. I didn’t mind the purple tint for this project, but if I wanted to be sure of a pure, clear polish, I would have used Spirit Thinners.

First up, mix your sanding sealer – what’s the point of that I hear you ask? I mean we’re going to slap this sealer on our piece and then just sand it off – why bother? Well, it soaks into the wood raising and hardening the wood fibres, which then are easier to sand off and it fills the grain in the process. Which means the end result will be smoother. It also stops the following coats of polish from being absorbed into the wood, which gives a better shine. So if you like really smooth shiny things (and who doesn’t) use sanding sealer!

Sanding sealer: 1 part Shellac to 5 or 6 parts methylated spirit.

Put the ingredients in a glass jar, give them a stir and a shake and leave them until the shellac has dissolved. This might take a few hours. Persuade it a bit by agitating it occasionally. Don’t worry too much about getting the measurements exact, vaguely right is good enough.

Label and DATE THE JAR! I know it’s not jam, but it still goes off. After 6 months it might not dry properly, which is why it’s so much better to make your own sealer and polish, as who knows how long the ones in the shops have been sitting there for?

And unfortunately for those people living in sunnier places than Britain, it’s best to store it below 24°C (75 °F). So yes, it might rain a lot here, but at least we can store our sanding sealer and polish.

(Incidentally I’ve read that some folks prefer 1/3 shellac, 1/3 meths and 1/3 boiled linseed oil (not raw) for their sanding sealer – apparently it extends the drying time, useful for big pieces I guess, but I’m not sure what else – has anyone used this mix??)

The mix of French polish is referred to as ‘The Cut’, and is traditionally expressed in lbs per gallon; meaning how many lbs of shellac are dissolved in a gallon of meths. E.g A 2lb cut is 2lbs shellac dissolved in a gallon of meths. A 2 lb cut is very popular – and it's worth noting that the more shellac you add, the harder it is to work. Some folks use a 4lb cut for ‘knotting’ to seal that pesky resin in, when working with knotty wood.

Now I don’t know about you, but if I started storing gallons of meths in my loft I think the fire brigade might have something to say about it, and I’d have to be polishing night and day to use that up within 6 months.

So, scaling things down a bit, a good ‘cut’ to start with is:

French Polish: 1/4lb (113 grams) dissolved in 1 pint (500mls) of meths. 

(This is still classed as a 2lb cut but without using a gallon of meths! And to be honest for this project you could probably half this, as you’ll still have loads left over.)

Label the jar with the ‘Cut’ and the date, then shake and leave it, just like the sanding sealer. Some folks strain it through cheesecloth when it’s dissolved, but frankly I didn’t bother. Some recipes for French polish also suggest adding linseed oil and sandarac (a kind of natural gum) which helps improve resistance to scratches, but I left these out as well.

Lots of layers will give a deeper colour.
At the moment, the polish is slightly purple (from the meths). To get that deep red colour, wait till the shellac has dissolved and add some dye. To control the process, I dissolved some of the red dye separately in a small amount of meths, with a tiny bit of black. Add the black in really small amounts (it’s really strong) until you get a good colour – then add to the polish a bit at a time to get the colour you want.

Remember you’ll be layering up the polish so the more layers you put on, the deeper the colour will be. I must admit, that bit can be kind of addictive as you see the colour developing – just one more layer…

But before we can get anywhere near polishing, there’s a bit of sanding to do… all covered in the next post…

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