Welcome to part 2 of our series on wood types. This week I’ll be discussing oak & oak wood treatments. 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 around 20 years. 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?
Acorn of the mighty oak tree.
Treating Oak Wood
With regard 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 straightforward. 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.
Oak turned grey/silver by UV rays & water damage.
Oak barrels traditionally used for whisky and beer.
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:
- 1 coat of clear wood preservative
- Followed by 2 coats of Osmo UV Protection Oil 420 Extra
Osmo 420 Extra 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:
- 1 coat of clear wood preservative
- Followed by 3–5 coats of high-quality tung oil such as Morrells Tung Oil
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 clear Osmo UV Protection Oil 420 Extra
If blackening on exterior oak needs removing, then scrubbing with a fungicidal wash such as Barrettine Mould and Mildew Cleaner is recommended. On the other hand, it may be the silvering that needs removing. If so, a scrub with Osmo Wood Reviver Gel (which contains oxalic acid, amongst other active ingredients) is recommended.
Unfinished oak.
Treated oak.
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 a 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 dampen an area by applying some water with a clean cloth or sponge. The look achieved when the wood is damp/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. A more natural look can be achieved by using wood oils that have been specifically formulated to retain the natural appearance of interior oak. These products include:
- If an oiled finish is preferred, then apply two thin coats of Fiddes Hard Wax Oil Natural or Osmo Polyx Oil Raw.
- If a varnished finish is preferred, then 1 part Manns Classic Wood Dye can be mixed with 50 parts Manns Extra Tough Interior 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 wax, whereas 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 Osmo Polyx Oil Tints or Fiddes Hard Wax Oil Tints are ideal because they colour and protect 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.
Oiling Consideration
If oak is being oiled, it is a good idea to sand it with 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 can reach heights of up to 40 metres.
- Oak trees regularly live to be 500 years old, although 1,000-year-old oaks are also known.
- A mature oak tree can produce up to 50,000 acorns!
Need help finishing a project made with oak?
For more help and advice on how best to finish oak, contact our team of resident experts who are always on hand to help with project advice and product recommendations.
We love to see before, during and after photos of any wood finishing project. If you would like to share your project pictures with us and our followers, you can either send us some photos or share on our Facebook, Twitter, Pinterest or Instagram pages.
469 comments
Hi. We have an oak framed extension on our house that has now started to darken after 2-3 years. What’s the best action please. Should I sand back and preserve or will putting on a mould resistance treatment pull out the black.
I clear wax annually but it is still blackening with the British weather and south facing sun.
Please advise what’s best and if sanding what grades to use.
Much appreciated
Reply to Craig Keyworth:
Hi Craig,
Can you explain what you mean by ‘darken’ please. Is it an overall, general darkening of the wood or black patches? Do you know what product was originally used and can you tell us what you are currently using annually to treat the wood? Some pictures would also be helpful. Please use our contact us (https://www.wood-finishes-direct.com/pages/contact) page to send us some details or alternatively, give us a call and speak with one of our in-house experts to discuss this further. Once we have a better understanding of the issue, we will be able to recommend some actions and what products will be needed.
If it is indeed mould, the wood should be stripped then treated with a mould and mildew cleaner such as Barrettine Mould and Mildew Cleaner (https://www.wood-finishes-direct.com/products/barrettine-fungicidal-wash-multicide). This will clean and kill off any active or dormant mould spores in the wood. It can then be refinished with an exterior wood oil that provides UV protection. Osmo UV Protection Oil Extra (https://www.wood-finishes-direct.com/products/osmo-uv-protection-oil) is a popular choice and is available in both clear and colour tinted options.
In terms of stripping the wood, it depends on what products have been used in the past. sanding will work but if the wood has been waxed, the sandpaper will probably clog up quickly and will need changing frequently. do not sand any finer than with a P120 to P150 grit sandpaper. If the wood is sanded to finely, it will prevent or restrict the oil from penetrating into the wood grain.
I hope the above helps but feel free to contact us (https://www.wood-finishes-direct.com/pages/contact) with further details and to get further guidance with your project.
I have some fine internal oak doors which are about 20 years old, the two middle doors open outwards and fold backwards so that on nice days they can be open and facing the garden.
All of the doors could do with a revarnish, but as you can appreciate, the middle doors have faded quite a bit more than the rest because of their external exposure to the sunshine.
Can you please advise me how to best go about preparing and revarnishing the doors, and if there is any way of ensuring that the revarnished door colour looks consistent throughout.
Many thanks
Mike
Reply to Michael Arnaouti:
Hi Michael,
As the doors are being refinished, am I right in assuming that they are all being sanded back to bare wood? Sanding and re-varnishing all the doors will result in a better matching finish across all the doors. The colour of the doors that have faded the most will likely require a slightly more aggressive sanding, starting with perhaps a p40 or p80 grit sandpaper and working up to a p120 or p150 grit. This will remove the UV damaged surface fibres of the wood and reveal the naturally coloured wood beneath.
Once the doors have been sanded, they can be re-finished with either a wood oil or varnish that contains UV filters or stabilisers. This will help to protect the wood and will slow down the colour bleaching process caused by the suns UV rays, a little like suntan cream.
In terms of a tough, durable varnish that is suitable for both interior and exterior wood and contains UV filters, consider Polyvine Heavy Duty Extreme Varnish (https://www.wood-finishes-direct.com/collections/polyvine). This water-based polyurethane varnish is extremely tough and durable and is available in a dead-flat and satin finish.
I hope the above helps but if you would like to discuss this project further with one of our in-house experts, please feel free to contact us (https://www.wood-finishes-direct.com/pages/contact) at any time.
Kind regards,
I am building a green oak porch. I know that it is detrimental to treat it before it naturally dries out. This may sound stupid but, in order to retain the colour could it be treated on the front side , thus allowing it to dry out on the other 3 sides ?
Reply to Stephen Wilshaw:
Good Morning Stephen, thank you for getting in touch with your enquiry and I can see the logic in your theory, however I would still probably not advice it. Blocking one side will just prevent that side from drying out and could possibly cause warping in the wood, depending on thickness and exposure. My advice will be to allow all surfaces of the wood to dry out. It is always difficult with green oak the wood will naturally silver before you are able to put any product on it.
There is the option of once it is dry that you can use the Wood Reviver Gel (https://www.wood-finishes-direct.com/products/barrettine-wood-reviver) to get some of the original colour back to the wood, test areas are always recommended. And then consider application of a protective finishing product, colour will help to slow down any further UV damage as the pigments act as sunscreen.
I hope all that helps and if you do need any further advice please do not hesitate to get in touch.
Kind Regards Samantha.
Reply to Samantha Taylor:
Hi Samantha,
Many thanks for getting back. I thought that may be the answer. I’ll put the tin of OSMO in storage and test the moisture content periodically. The wood is 22% at the moment. I don’t suppose you know, approximately, what percentage it would dry out each year do you ?
Best regards
Stephen
Reply to Stephen Wilshaw:
Hello Stephen,
It would be difficult for me to predict as the age, thickness, environment are all factors in the drying of the wood. There is a general consensus that one inch per year is the drying time of green oak, but again I would not say this is a given. And actually if your wood is at 22% then it has dried afair amount already, it will be ready when it settles at its general level of moisture in the environment.I am sorry that I can not give a more definitive answer, just keep an eye on the wood and keep measuring, you don’t have long to go, I don’t think.
Kind Regards Samantha.
Hello,
We have an oak staircase which has a shiny look and feel to it so we think it has been varnished. We would love to remove the varnish and get it back to looking like unfinished/ natural oak.
Please can you tell me the best way to go about this?
Reply to Zoe:
Good Afternoon Zoe,
You could look at a stripper such as the Paint Panther Paint and Varnish Remover (https://www.wood-finishes-direct.com/products/barrettine-paint-panther-paint-varnish-remover) this is a quick working gel that makes the varnish bubble up to be scraped off. A light sand with a 120 grit and a wipe over with Methylated Spirits and you should be back to bare wood.
You can then look at application of a Fiddes Hard Wax Oil (https://www.wood-finishes-direct.com/products/fiddes-hard-wax-oil) which gives a natural look and feel to the wood, as well as great protection. Sample sizes are available and I would recommend this as the wood type, age and condition will all impact on the over all finish result.
For further advice please feel free to get in touch via or contact us (https://www.wood-finishes-direct.com/pages/contact) page.
Kind regards Samantha.