My thoughts on Finishing

[JohnB]

Finishing,
G'day all, there have been a lot of positive comments made regarding my finishing of projects, and I thank you all.

I'll try to pass on some of my techniques and the reason behind them.

Please bare in mind that this is what I was taught while doing my Cabinet making and Furniture design apprenticeship over 35 years ago.
I only mention this as products and tastes do change with time.

The reasons for Finishing
1. Protection of product
2. Allow cleaning of product
3. Enhance natural timber colours and grain.

The number one thing to keep in mind is "The finish is only as good as the preparation"
When sanding timber, you can only sand it as smooth as the pores will allow. What this means is that there becomes a stage where you can not get the wood any smoother no matter what grade paper you use. It may feel smoother, but what is happening is the fine dust is filling the pores and grain and when you remove this dust prior to applying a finish, the timber will return to it's smoothest attainable state.
As a general rule, 240g - 280g for hand sanding is sufficient, as you must sand with the grain.
If using a Palm sander or ROS 320g is probably more than fine enough.
It is important that as you go through the paper grits to get you final finish, to dust down the project between grit changes.
Eg. When you swap from 80g to 100g dust own the piece properly or else what is likely to happen is some loose grit from the 80g will stay on the work piece and the 100g will move that around under the paper, thus producing swirlies.

GLOSS = SMOOTHNESS
When applying the first coat of any type of finish, you will notice the grain will raise (Varying amounts depending on product and Timber) this is called the Bloom.
Sanding this coat down when dry to remove the bloom requires 240 - 280g paper. Sanding with the grain. If, because of the design of the project it is not possible to sand with the grain a finer, 320g, paper should be used.

The trick from now on in is to fill the grain, without giving the item a plastic look.
To achieve this, light coats of finish are better than thick ones, and cut each coat back with 280-340g paper.
Dust of, either with a soft brush, slightly damp cloth or compressed air, and apply another coat.
Cut this coat back and apply a third.
Your project will now be becoming smooth, and glossy and shouldn't look like it's been wrapped in cling wrap.
Another coat or two may be required if the timber is an opened pore variety.

SATIN and SEMI-GLOSS
The exact same technique is used as above except the product you use will be designed to give one of these finishes.

If you purchase your finishing products in large containers and use varying gloss's it may be beneficial to purchase only a semi-gloss finish.
The flattening agent will settle to the bottom and by scooping the product of the top off the can you will have gloss and by stirring you will have a satin finish.

Remember, Timber is very tactile and purchasers will like to feel it. So it MUST not only look smooth it must feel smooth.
Just think how many times you have looked at a piece of furniture and ran your hand over it.

Another thing to consider is the ease of cleaning.
If pores are left open dirt will accumulate in the grain and the item will require much more effort to clean.

Hope this helps out a bit and gives a bit of material for thought.

[campasano]

John thank you for the tips, I will store them in my folder...MIKE

[Tor]

Good ideas and tips. Thank you for sharing.

Tor

[Rolf]

Thanks John

[Doc249HMCS]

Good advice, John, Thanks

[Mike Crosa]

Thanks John, excellent primer.

[stevebuk]

great info john, could i ask what finish you would use on 1/2 inch Oak. I have been using gloss varnish, but i feel its too thick and dont like the way it goes on, or is there a way to thin it down.
thanks..

[GrayBeard Phil]

John:

Very well written. Thank-you for spending the time to compose that excellent post.

I do have only one, very minor, point of addition to add. I suggest you add that the finish selected should not conflict with the intent of the project. If the project is all about the missing pieces of the fretwork, then the finish should not draw attention to the wood itself. Very shiny wood (gloss or semi-gloss) draws the attention of the viewer, but a matt finish (or maybe a satin finish) will divert attention away from the wood.

You may disagree, John.

Steve:

Can you purchase a spray can of Lacquer on your side of the pond? Or can you get a spray gun to apply your varnish?

A light spay coat may solve your problem. Brushing Varnish goes on thick so the chemicals that cause product 'levelling' (flattens out brush strokes during drying and curing) to function. Spay applications goes on with a lot thinner finish coat.

Phil

[PuzzledMoose]

Originally Posted by GrayBeard Phil

John:

If the project is all about the missing pieces of the fretwork, then the finish should not draw attention to the wood itself.

Phil

The holes are the easiest bit to finish though ...

Seriously, thanks for the post, John. I've been sanding a few smal bowls down to around 800 grit as an experiment - dry sanding to 320 and then oiling the bowl with mineral oil between other grades. Gives a nice surface - smooth a baby's bum .. no idea why it seems to work though.. ..

[JohnB]

G'day Steve,
Like Phil says.
Varnish is inherently thick as it is designed to be brushed and self levelling.
I'll assume the finish is a polyurethane type, and if so you can give this a try on some scrap.
Thin some to about 50% with turps, stir well, and using an old soft cotton rag eg TShirt, dip it in the varnish and wipe it on. Wipe with the grain and only go over the piece once or twice. you do not want the Poly to start to go tacky while applying it. Let it dry, cut back and reapply. Do this 3 or 4 times and according to Hoyle you should have a nice gloss looking project with out the glad wrap look
Keep a small paint brush handy to catch any runs on the inside of frets etc.

Phil,
I do agree with you. I like to give most of my small hanging items a satin type finish and larger pieces such as furniture I usually use a gloss. Some things however tend to be traditionally gloss such as Jewellery boxes, especially those made from Dark wood.

Ian,
I think what is happening is that the dust and mineral oil is forming a slurry and being forced into the pores and grain. As you sand with the finer papers the slurry becomes finer and so can fill smaller gaps. There is also probably an element of burnishing like mentioned in another thread. I have heard of this method of polishing, using oils but have never tried it.

Just some ideas.