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 Sam,
I’ve got a white oak table with a few darkish brown marks on it and some slight black water damage from condensation on a glass. Two of the marks are where some olive oil was dripped and not wiped off properly during dinner. They’re not exactly horrific, but they’re annoying me! Do you think necessary to have to remove the finish and re-apply a new one or is there a trick that I’m missing? I live in an apartment and am reluctant to do some sanding inside. I would be ok dropping the shade of the table slightly, it would probably then match the oil marks. I can then keep topping up over the years to prevent further marks appearing. But, ideally, I’d rather keep it as light as possible! Any help would be massively appreciated.
Reply to Darren:
Hello Darren,
It will depend on what the current finish is on the table. An oiled finish can be patch repaired by simply sanding back the effected areas and re oiling with the same or a similar oil. If the table is varnished this is unfortunately a harder issue to repair and will need fully sanding back to bare wood in order to remove the marks and re varnish or oil. Feel free to let me know if you know which product is on the table or if you have any further questions. Or you can email me direct at wood@finishes.direct
Many Thanks Samantha.
Thank you Sam. So would you suggest the natural 429 is better to keep the natural freshly sanded look over the clear 420? I could buy a pot of each and test obviously but just wondered on your advice. Thanks again for your help.
Hello. I have just had some new oak sleepers and two 8ft oak gate posts put in my front drive. I have started to sand the gate posts and they finished look is exactly as I desire. How do I treat it and keep it looking as smooth and unfinished as possible? I have looked at previous posts and wanted to check if it’s a coat of wood preserver, 2 coats of osmo extra clear? I read about the white product or something but got a little confused. Any help would be appreciated. Thank you.
Reply to Ryan:
Hello Ryan,
Yes a wood preservative such as Osmo WR Base coat (4001) (https://www.wood-finishes-direct.com/products/osmo-wr-base-coat) or an alternative exterior wood preservative (https://www.wood-finishes-direct.com/collections/wood-preserver) is the best way to help prevent mould, mildew and rot. Once treated and allowed to fully dry, the wood can then be treated with two coats of protective oil to give UV protection and water repellency.
Osmo UV Protection Oil Extra 420 (https://www.wood-finishes-direct.com/products/osmo-uv-protection-oil) is a clear finish that will darken the wood slightly to give what we call the ‘damp look’ and the natural 429 contains a small amount of white pigment that counteracts the darkening of a clear oil to leave the wood looking more natural in colour. Test areas are vital as the natural is not always suitable for darker exotic hardwoods and may leave a slightly milky looking finish.
I hope that helps and if you have any further questions please do let me know.
Kind Regards Samantha.
We have had some landscaping done with some chunky oak edging (5″ × 10″).
Within weeks we can see some blackening, and also some ‘mould’ appearing
We do want to oak to go silvery over time….& do NOT really want to be oiling it every year – any advice, or have we made a massive (expensive!) mistake?!!
thanks!
Reply to MikeW:
Hello Mike,
To tackle the mould you are getting I recommend using Barrettine Mould and Mildew Cleaner (https://www.wood-finishes-direct.com/products/barrettine-fungicidal-wash-multicide). This will remove the black that has resulted from water ingress.
Once clean and dry an oil will be the best option. However regular top ups are the best way to slow down the silvering process of the wood. Osmo UV Protection Oil Extra (https://www.wood-finishes-direct.com/products/osmo-uv-protection-oil) is a clear oil that has UV filters in it and is a good option if you want a clear finish. It will also help to make the wood water repellent. I would also recommend Osmo WR Base Coat (https://www.wood-finishes-direct.com/products/osmo-wr-base-coat), a preservative that helps to prevent mould, mildew and rot.
To slow down the silvering process even more applying a colour will help, even a light colour will improve the UV protection and the darker the colour the more protection in the same way as the higher the factor in sun cream the more protection you get.
An alternative option is Sikken Cetol Filter 7 Plus (https://www.wood-finishes-direct.com/products/sikkens-cetol-filter-7-plus) which is a coating system, much like an exterior varnish. This product requires less maintenance than an oil, typically 3 to 5 years depending on location and weathering, but must be maintained to ensure that the coating stays intact. Unlike a wood oil, if the coating starts to crack, flake or peel, the old finish must be removed and the wood prepared again so that a new finish can be applied.
If you have a look at the recommendations and let me know if you have any further questions.
Kind Regards Samantha.
Hi, we have just had some oak worktops installed in our kitchen. When they arrived they were a lovely light colour. We used Rustins clear worktop oil and they have now gone a dark brown colour. Although I know some people like this, I was really after a very light un-oiled look. Is there anything I can do to change them? Thank you! Jas
Reply to Jas:
Hello Jas,
Clear Oils will often darken the wood to give what we call the ’wet look ’ to avoid this we have a product called Osmo Top Oil (https://www.wood-finishes-direct.com/products/osmo-top-oil) in natural.
The Natural has a small amount of White Pigment that will counteract the darkening effect. You will need to remove the current oil and this can be done by scrubbing with a White Spirits such as Barrettine White Spirit (https://www.wood-finishes-direct.com/products/barrettine-white-spirit) and a Woodleys Finishing Pad (https://www.wood-finishes-direct.com/products/woodleys-finishing-pads).
Once back to bare wood then two very thin coats of the Natural Oil can be applied, a test area should be carried out first. If you have a read up of the product and feel free to get back to me.
Kind Regards Samantha.
We have two oak pillars supporting an overhang on our courtyard and the pillars have not been kept protected. There are cracks, greying and areas where the previous stain/sealant? remain. Please, how can we clean these up and refinish them?
Also have a lovely oak table that has water rings on it from flower containers. How can we restore the table top?
Thank you.
If you have already covered these questions on the website I apologise for repeating them, my eyes have got rather tired trying to scan the Q & A.s …..