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
Reply to lydia:
Hello Lydia,
The Oil that you have applied can be removed using Barrettine White Spirit (https://www.wood-finishes-direct.com/products/barrettine-white-spirit). You may need to do some light sanding as well but a majority will come off with a good scrub, using some finishing pads and then you could apply a product such as Osmo Top Oil Natural (https://www.wood-finishes-direct.com/products/osmo-top-oil) this is still a protective Oil but is design not to darken the wood as much.You should always do a test area first to ensure that you like the finished effect. Hope this helps and you get the finish you are looking for.
Dear Sam/ Nick,
Thank you for this extremely useful advice on oak finishes. It has been a pleasure to read!
I am an architect and we are specifying a lot of high-quality external joinery in European Oak and Oak glulam for a big project in Cambridge. We would like all the oak to be pre-weathered or bleached so that it has the silvery weathered appearance from day one. Research has led us to an American product called Cabot Bleaching Oil but they will not ship this from the US to the UK. Therefore we need to find an available alternative.
Are you aware of products that may be suitable? Ideally we would find something that does not require ‘staining’ the oak grey to achieve the weathered appearance. The Contractor has suggested Osmo Natural Oil Wood Stain (silver grey 905) but it would be good to find a ‘bleaching’ product.
Would the 1 coat clear wood preservative and 3-5 coats tung oil be suitable?
Many thanks for your help.
Tom
Reply to Tom McG:
Hello Tom,
My apologies in the delay in getting back to you, I have been speaking to our wood finishing expert Merv about this one as its not something I know a lot about. Here at WFD we don’t do any bleaching products or really encourage people to use them, but merely to allow the natural weather process to occur, if you would like that silvered effect. You can do this by using a clear product that doesn’t have UV filters in it such as the Osmo Decking Oil (https://www.wood-finishes-direct.com/products/osmo-decking-oil). And I would recommend using the Barrettine Premier Wood Preservative (https://www.wood-finishes-direct.com/products/barrettine-premier-wood-preservative) as a first coat treatment before the Decking Oil I appreciate that in your case you may not have the time to be able to do this and as suggested the Osmo Natural Oil Wood Stain 905 will be the closest finish that we would recommend. You should do a test area as I’m sure you are aware different woods will take have an effect of the final colour that is achieved. I hope that your are able to get the look you require.
Hi Sam
15 years ago, in return for a donation to the charity, the Woodland Trust provided a bench in memory of my belated parents which was sited in woodland in Yorkshire. It was made from a recently felled oak, and was or rustic design, with the both the seat and backrest sawn about 4" thick from the trunk. The planks retained the sapwood and bark on each edge. On each pilgrimage to the bench, the family lovingly applied oil, but this has done little to stop the sapwood rotting out (the heart is still sound) and the bench needs replacing. If we replace “like for like”, what is the best way to treat a bench made from unseasoned wood.
Thanking you in anticipation. Richard.
Reply to Richard:
Hello Richard,
Thank you for your inquiry, because the wood is new it will have a high moisture content and so is unlikely to take a protective product such as an Oil or varnish initially . What I would recommend is to use the Premier Wood preservative for a couple of years until the wood has weathered more and able to take a product such as Osmo UV Protection Oil Extra (https://www.wood-finishes-direct.com/products/osmo-uv-protection-oil) which is durable hard wearing product. It would need a maintenance coat every 2/3 years dependent on weathering and general wear and tear. Hope this helps – Sam.
Hi Sam
Thanks for reply, I added your suggestion to my basket, but before I complete can I ask one more question. I have used pine planks about 20mm x 200mm for the horizontals and found in the past they have over time warped across the width to kind of curl. Can treating stop this?
Dont want to postage costs, so if this is treatable I can order at the same time.
Thanks for your time
Jamie
hello sam
i am a builder and the architect has specified a no. of european oak feature walls externally.
he does not want a shiplapped or weatherboard look so i was thinking of using an engineered floorboard with a 6mm oak veneer and then sealing it with an oil based marine varnish, do you have any advice on this.
thank you in advance.
regards
matt
Reply to matt:
Hello Matt,
I had a word with some of my colleagues about this one and we all agree that this would not be a viable option that we would recommend. We believe de-lamination would occur sooner rather than later and would not provide adequate protection. It is difficult for us to advise you on this as we are not specialist in cladding or external features, but rather the best finishing products to use. It has been suggested however that you would be better off using solid Oak tongue and groove, that should be treated with a good quality finishing product on both sides before installing. We would recommend the Sadolin Quick Drying Wood Preserver as a first coat protective treatment and then a product such as Sadolin Classic Wood Protection (https://www.wood-finishes-direct.com/products/sadolin-quick-drying-wood-preserver) followed by Sadolin Extra Durable Clearcoat (https://www.wood-finishes-direct.com/products/sadolin-extra-durable-clearcoat) Sadolin produce the best exterior varnish due to its flexibility and durability. Hope this helps – Sam
Hi Sam
I have purchased some untreated planks of European Oak to make the uprights to shelf units (indoors) and want to keep them as natural as possible.
It looks like a clear wax is possibly the answer, I have some Autentico Furniture Wax in the garage, but not sure this is suitable.
Considering the outlay for the oak I want to protect it best I can and would rather spend a little more to treat it correctly.
Many Thanks – Jamie
Reply to Jamie Tully:
Hello Jamie,
A wax will give the wood a great natural finish but minimal protection. But you might want to consider a hard wax oil such as Fiddes Hard Wax Oil Natural (https://www.wood-finishes-direct.com/products/fiddes-hard-wax-oil-oak-lightening). This product will give more protection than a wax and still leave a Natural look to your wood. A little oil goes a long way as it must be applied thinly and worked in to the surface of the wood with any excess or surface oil being wiped off. Hard wax oils are very durable, easy to apply, maintain and to patch repair worn areas if required.