Finishing Products.

Why Use a Finish?

The three most common needs that a finish serves are:

Protection,  Stabilisation and Appearance.

Protection is basically keeping things clean and helping ward off dings and dents.

Wood with a finish will limit the amount of dirt and handling discolouration.

Stabilisation is the prevention of water absorption  and also where you apply colour to prevent oxidation and fading. However, the finishes that are used by Woodturners will not completely stop this process but will slow moisture transfer

Appearance – yes the finishing products we use can help appearance by the amount of shine we want or the colour we want on our finished piece.

So how do we select a finish – most of the time we select based on experience – If you’ve done it before and it was successful then that tends to make us use that finish again.

This is where being a new turner can be a help – you’ve no previous preferred finish and are open to new things.

I suggest you select your finish on end use remembering that if the piece is to be used with food it must be food safe!

A decorative platter to be displayed in the cabinet can have a very fine finish that doesn’t provide any mechanical protection. It won’t be handled and only needs occasional dusting.

A pen will need the toughest most durable finish you can apply

Looking at what might be called “the basic finishes” we have what Mark baker in his book “A Craftsmans Guide”  calls:

Penetrative finishes – which are basically oil finishes.

Semi – Penetrative Finishes – waxes

Surface Finishes – Sanding sealers, Lacquers and Varnishes.

Polishes – Products to enhance a finish

So this is the way I want to look at them tonight.

First – Penetrative finishes :

There are a number of oils on the market most of them have additives included to aid the chemical process.

Raw oils – Mineral oils, raw linseed, sunflower,  etc are non drying oils  they never really dry out.

The ones marketed for Woodturners all are a blend of oil, thinners, drying agents and whatever the manufacturer put in to distinguish their product.

Most oils will darken the wood so it’s always a good idea to use a test piece.

Understanding how oils works can help us to use them.

Oils are small molecules which soak into the pores of the wood and with time they polymerise into larger molecules with exposure to the air what we call drying.

As with most finishes we need to be aware of the climate around us avoiding conditions that are too cold as this will delay the chemical change.

The best method of applying oils is to flood the surface of the wood keeping the surface wet for about 20 mins letting the wood absorb as much oil as it can after this time wipe any excess oil off the piece and let it dry. Repeat the process reducing the time the oil is left to stand before wiping dry occasionally using fine grit abrasive with the oils as a lubricant. The slurry created can fill any tiny pores of the wood creating an even smoother finish.

Oil finishes can be buffed to the desired gloss level you require and most are toy safe and the majority food safe – But always check the labels.

Sem-Penetrative Finishes:

 These are our wax finishes.

They only penetrate the top millimeters of the wood and they can be used ether on the bare wood or over the top of an existing finish   (S.Sealer).

Depending on the wax used they usually give a good protection.

Again there are many waxes on the market and they are extremely versatile.

Wax is fast, inexpensive, dries in minutes.

It can be applied on the lathe or after the work is removed

It can also be used as a sanding lubricant or  with abrasive added as a final abrasive (Yorkshire Grit)

It can be used to add colour or enhance grain (gilt cream)

The finish is renewable – as the finish wears it can be touched up.

It can be applied with steel wool, Scotchbrite pads, lint free rags or kitchen paper – a shoe brush, Rag, kitchen paper or buffing wheel allows the wax to be brought to various levels of gloss.

However, wax isn’t perfect:

It will build up in voids scratches or any surface irregularity – You cannot hide bad work under wax.

It isn’t heat resistant and is not a durable finish.

The soft nature of wax can trap dust and dirt

We now have Microcrystalline Wax which does give increased protection against finger marks etc.

Most waxes and a blend of Beeswax, oils, Carnuba Wax and are generally known as Paste Waxes (Woodwax 22)

Some Paste Waxes are coloured (Liming Wax)

Carnuba Wax – derived from a S.American plant a hard wax normally mixed with beeswax to produce a high gloss finish.

Hard Stick wax normally applied with the lathe running to melt the wax onto the wood – care needed to avoid too much build up

Surface Finishes

These include Sanding Sealers, Lacquers and Varnishes.

They can be wiped, brushed or sprayed on.

Sanding Sealers

 Shellac

This product has been around for many years – It’s the basis for French polish and when I used to do Antique furniture renovation I used to use it a lot. However, now I very rarely use it as it does take some time to dry and cure sufficiently fully.

It has now been largely superseded by Cellulose Sanding Sealer which dry more quickly and more evenly that shellac

Cellulose Sanding Sealer can be used as a base coat to give a protective layer for most other finishes.

CSS can be used neat from the tin, however as it dries quickly this can produce streaks if if worked too much. I find it best diluted with cellulose thinners. – You can dilute it by up to 50%, but a 70 – 30 dilution is better.

If you do dilute it make sure you get a good brand of thinners – Thinners bought by the gallon from a car body shop may well be reclaimed thinners containing traces of water which can cause blooming in your finish!

Acrylic Sanding Sealer:

This is a relatively new product. They dry quickly and are easy to use. It is used when using acrylic paint or lacquer as a top coat.

They are best used in spray form.

Melamine:

Use Cellulose Sanding Sealer as a base coat to ensure a sound bond.

Melamine lacquer is cellulose lacquer with a melamine additive and is designed to be applied over the top of cellulose sanding sealer “basecoat” as part of a “system”.

The active ingredient is a pre-catalysed melamine resin.

It gives a hard glossy durable and water resistant finish.

It dries relatively quickly but can take up to ten days to cure completely.

It come in both tins and sprays.

If using from a tin, do not shake the tin as this produces air bubbles in the lacquer which can cause an orange peel effect on the finished piece.

If using a spray then give the can a good shake as it has a propellant in it and the spray eliminates the air bubbles.

 Lacquers

Acrylic Lacquer (Gloss & Satin)

A Lacquer is a clear or coloured varnish that dries to produce a hard durable finish.

Thy are available in spray or liquid form. For Woodturners the best form is the spray as this produces a very light coat and the application of several light coats is better that one heavy one.

As the name tells us they are acrylic based and are water soluble. They can be used over cellulose, spirit or acrylic substrates.

Cellulose or spirit products cannot be used over acrylic as these will dissolve the acrylic product.

All lacquers can be burnished to a high gloss.

Polishes

 Friction Polish;

 This is a shellac based product used to create a high gloss shine.

It should be applied sparingly with the polish being applied to the piece stationary on the lathe and then with the lathe going polish with a piece of kitchen paper.

Friction polish should only be used on small items as if used on larger pieces could result in streaking.

Friction polish is not a durable finish as it is easily marked and becomes dull.

Burnishing Cream.

This is a product that came from the automotive industry and is a liquid containing micro abrasives which cut very finely into the surface. They can be used on a variety of finishes however, beware of using them on open grained wood as they can leave a deposit in the open grain.

Polishing Mops & Buffing wheels.

These are used in conjunction with cutting and polishing agents to produce the required shine on many finishes.

These are available in a variety of sizes either stitched or unstitched and can be mounted on the lathe – a different mop being used with each cutting agent.

Bibliography:

Woodturning, A Craftsmans Guide. –  Mark Baker

Contemporary Woodturning – Nick Arnull

Woodturning Magazine – GMC Publications