What Everyone Should Know About Finishing Oak
Welcome to part 2 of our series on wood types. This week I’ll be discussing Oak. If you haven’t already read part 1, feel free to go check it out here: All about Pine Wood.
A little history of Oak
Oak(or quercus as it is known in Latin) is a hardwood with some 400 known species. It has always been a popular wood in The UK, but in recent times it is even more widely used in construction and also as internal fixtures in clubs and gyms etc. For furniture construction oak has become ever more the wood of choice, a trend expanding year on year since the year 2000 when China, India and Indonesia substantially increased their export markets. Pine has been the wood to suffer from oak’s popularity as it is more widely available in the Far East.
The flowers of many oak trees are known as catkins and they are produced by oaks when they reach their reproductive age which is typically aged 20. They are triggered by rising temperatures in spring. Ultimately it is the catkins of many oaks that turn into the acorns, so maybe that popular phrase… ‘mighty oaks from little acorns grow’ should be ‘mighty oaks from little catkins grow’ although it doesn’t quite have the same ring does it?
Treating Oak wood
With regards to finishing and treating oak there are numerous possibilities but there are certain requirements that are asked for time and again… Often we are asked how external oak can be kept looking natural. Whilst the question is easy, the answer is not so straight forward. These are the necessary considerations: -
- When water penetrates oak it reacts with the high tannin content within oak, resulting in ‘blackening’.
- The Sun’s UV rays will turn the oak to a silvery hue over time.
- Clear products are inevitably not completely clear so they tend to ‘bring out’ the natural colours of the oak, normally making it a bit darker and warmer.
- The levels of rain, wind and sun will make a difference to how quickly the oak changes colour.
If the requirement is to keep the oak looking as natural as possible, whilst preventing blackening or silvering as much as possible, then the following is the best system we know of: -
The Osmo 420 Wood Stain Protector offers UV resistance and also contains biocide which is important for external timbers as it prevents the wood from becoming diseased with wet rot, dry rot and blue stone etc. The oil also repels water, thus preventing it from going black.
If the requirement is to protect the oak whilst keeping the silvery appearance then the following is the best:
Tung oil is one of the clearest oils on the market and doesn’t offer UV resistance.
If the exterior oak needs to be coloured then the following system is recommended:
- 1 coat of clear wood preservative
- followed by 1 coat of your chosen colour of Osmo Natural Oil Woodstain
- followed by 1 coat of Osmo UV Protection Oil 420 Extra
If blackening on exterior oak needs removing then a scrub with a fungicidal wash is recommended, with various brands being available from DIY superstores and hardware shops. On the other hand it may be the silvering that needs removing. If so, a scrub with oxalic acid is required or even better, Osmo wood reviver (which contains oxalic acid, amongst other active ingredients).
One of the most common enquiries we get is how to keep internal oak looking natural. This is not just a case of simply applying ‘clear products’ as they bring out the natural colours of the wood, thus making it little darker and more golden. A very good indication of how your oak will look once it has been finished with a ‘clear’ coat is to apply water to a test area. The look achieved when the wood is wet is very close to how it will look once a clear varnish or a clear oil has been applied.
Some customers like the way oak colours when clear coatings are applied to it whilst others want it to be as close as possible to how it looks in its natural state. This natural look can almost be achieved by adding some white to your chosen top coat but test areas are vital because each wood needs a different mix of clear top coat to white. Here are some guidelines: -
- If an oiled finish is preferred then 1 part of the white hard wax oil can be mixed with 2 parts of the clear hard wax oil.
- If a varnished finish is preferred then 1 part white dye can be mixed with 50 parts clear varnish.
Clear wax polish is the one exception to the above… If a clear wax polish is applied to bare oak (or just about any other wood for that matter) then the colour is kept very natural indeed, it’s just a question of whether a wax polish is going to be durable enough. Internal doors, for example are considered, by most people, to be ideal for finishing with a wax, where as a floor will look nice once waxed but regular maintenance is required, so most people don’t opt for wax for this reason.
If the oak needs to be made darker then hard wax oil is ideal because it colours and protects the wood in the same application. It is always good to try and finish with a clear coat if possible because if the wood gets scratched it is the clear coat that scratches before the coloured coat and therefore the scratch is not as noticeable.
If oak is being oiled it is a good idea to sand it with a sandpaper that is no finer than 150 grit. The reason for this is that the pores of the wood are more open thus allowing the oil to sink into the wood better. Better absorption equals greater protection.
Interesting Oak Stats
- Oak bark is rich in tannin, and is used by tanners for tanning leather.
- Acorns can be used for making flour or they can be roasted for making acorn coffee.
- Tannin dissolves and escapes from the wood. Wine barrels are made from oak and it is the tannin that helps to give the wine its’ colour.
- Sessile oaks of Europe and can reach heights of up to 40 metres.
- Oak trees regularly live to be 500 years old, although 1,000 years old oaks are also known.
- A mature oak tree can produce up to 50,000 acorns!
For more information on Oak, see the following resources: -
Oakey Dokey then – tune in next time when we’ll be discussing………… Teak!