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.

Oak affected by the sun

Oak affected by the sun

Oak affected by rain

Oak affected by rain

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: –

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:

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:

If blackening on exterior oak needs removing then a scrub with a fungicidal wash is recommended. On the other hand it may be the silvering that needs removing. If so, a scrub with Osmo wood reviver (which contains oxalic acid, amongst other active ingredients).

Unfinished Oak

Unfinished Oak

Finished Oak

Finished 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 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: –

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.

Oiling consideration

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!

Oakey Dokey then :)  – tune in next time when we’ll be discussing………… Teak!

16 Responses to “What Everyone Should Know About Finishing Oak”

  1. Cheryl Emery Says:

    I have a raw oak dining table which I would like to leave as natural as possible. What should I treat it with to protect it whilst keeping it looking natural?

    Thanks
    Cheryl Emery

  2. peter davis Says:

    I have client who is considering using an oak dining table as a dining table in the garden. Is oak furniture treated with any finishes which would degenerate in an outdoor environment?

    Thanks Peter

  3. nick Says:

    Hi Cheryl,

    As the table is bare wood, a couple of products to consider would be Fiddes Hard Wax Oil Natural or Osmo Polyx Oil Raw 3044. Both of these products are designed to keep freshly sanded or bare wood looking very much the same while offering a good level of protection. Both products are resistant to heat such as hot plates and cups and completely food safe so ideal for a table.

    These products are available in a sample size and depending on the size of the table, one or two sample pots may be enough to complete the project.

  4. nick Says:

    Hi Peter

    The first thing to establish is does the oak table already have a finish such as an oil, wax or varnish? Is it bare wood or going to be sanded back to bare wood?

    If it is bare wood or being sanded back, the wood can be treated with two coats of a clear wood preservative such as Barrettine Premier Wood Preservative followed by two coats of Osmo Teak Oil. This combination of products will help to protect the table from things such as mould. algae, dry rot and other wood related pests and diseases.

    Pay special attention to end grain such as the bottom of the legs. These can be dipped in the preservative for several hours or overnight so that the preservative can penetrate deeply into the base of the legs to offer the best protection. Once the preservative has fully dried (24 to 48 hours) apply the Osmo Teak Oil, again giving the bottom of the legs extra attention.

    Always follow the instructions on the tin.

  5. Stuart Martin Says:

    Thank you Nick for a very useful post. Please can I ask whether your recommendations apply to something a little more architectural – such as external oak weatherboarding on a barn, or an oak door in an oak boarded wall? In these situations I would like to put up new oak boards and joinery, and have it weather to silver ASAP. Should we go for your preservative + tung oil option, or will this stop the oak from silvering?

    Thanks, Stuart

  6. Lauren Says:

    Hi
    We have some oak we are planning to sand (as very rough at the moment) and use as a fireplace surround with a wood burner in situ, we want to keep looking as natural as possible and not have a very shiny finish, would clear wax polish be the best or hard wax oil as hear resistant better?
    Many thanks

  7. Catherine Says:

    Hi we have raw European Oak beams and I would like to know what to finish them with they are have been drying out and cracks some large have appeared .. we don’t have heating in the room where they are at the moment but shortly will have…. How can I prevent any further cracking crevices from appearing ?…. What could I use to enhance the wood…. So much information out there and want to use the right information so as not to damage the wood…

  8. nick Says:

    Hi Catherine,

    The best way to help prevent Oak beams from cracking and splitting is to feed the wood with an oil or wax based product. I see in your question that you would like to ‘enhance the wood’. A product that will do all of these things is Osmo Polyx Oil. This will enhance the natural grain and colour of the timber while also feeding the wood with a blend of natural oils and waxes. A good way to see how the beams will look with the oil before purchasing is to wipe a section with a damp cloth or sponge, the appearance of the wood when damp is a good indication of what it will look like with the Polyx Oil on.

    If you prefer to keep the natural, untreated appearance of the wood but with the benefit of being protected, Osmo Polyx Oil Raw would be a good alternative.

    I hope the above helps and good luck with your project.

  9. nick Says:

    Hi Lauren,

    If you plan to keep the wood looking natural as in freshly sanded, the best product to use is going to be Osmo Polyx Oil Raw 3044. This product gives a matt finish so it’s not shiny and helps to keep the wood looking natural. Polyx Oils also have good resistance to heat and can be easily replenished with a fresh coat of oil if the wood starts to look like it is drying out. Simply apply 2 thin coats and allow to fully dry before exposing to heat.

    If you were to use a clear oil, it will darken the timber giving it a damp look and draw out the natural grain and colour of the Oak. Depending on the age and type of Oak, this could give the timber a golden or reddish appearance, not what you are looking for.

    As with any of the products we offer, always do a test area and follow the instructions on the tin.

  10. nick Says:

    Hi Stuart,

    A good combination for your weatherboarding, Oak door and Oak boarded wall, that will give good protection while allowing the timber to silver would be 2 coats of Barrettine Premier Wood Preservative in Clear, followed by 2 coats of Barrettine Log Cabin Treatment. The wood preserver will protect the wood from the biological threats such as mould, algae and insect attack while the Log Cabin Treatment offers protection against wind and rain. As neither the wood preserver or Log Cabin Treatment contain any UV filters, the timber will silver naturally.

    I would recommend the Log Cabin Treatment over using Tung Oil as although it is more expensive, it has better durability and will not require re-coating as often.

    If possible, it’s always a good idea to soak the end grain of the timber in the preservative so that it reaches saturation and then the same with the oil ones the preservative has fully dried (allow 48 hours) as it is normally the end grain that is most susceptible to the elements.

    As with any project – Always follow the manufacturers instructions on the tin and always do a test area first.

  11. Becca Says:

    Great, comprehensive article. – Just what I needed.
    Thank you !

  12. Becca Says:

    Hi Nick,

    Thanks again for all the info. I have one more question if that’s ok…

    I am building some shelving units in a bathroom and using a variety of oak floor boards. Most of the boards are untreated and previously unused, while a couple have had some kind of varnish or other treatment which I will sand down.

    Based on your article and answers above I thought I would begin with a clear wood preservative (because of the humidity and occasional splashed water in a bathroom) and then follow with either Osmo Polyx Oil Raw or Fiddes Hard Wax Oil Natural as I want to keep the natural, pale colour of the wood.

    So my question is, in this situation will these two finishing products keep the natural look as you suggest, or will the preservative darken or warm up the colour?

    Or maybe clear wax polish would be suitable in this situation? I wouldn’t mind the maintenance, but I want something which will prevent too much staining from water.

    Thanks so much.

  13. nick Says:

    Hi Becca

    The best way to protect the wood from the damp conditions while retaining the natural sanded look is to apply 2 coats of Barrettine Premier Wood Preservative initially, followed by 2 coats of Osmo Polyx Oil Raw or Fiddes Hard Wax Oil Natural.

    Where possible, try to treat all parts of the wood i.e. both sides, edges and especially the end grain. Although these products are touch dry within several hours, allow 24 to 48 hours drying time between coats of the preservative and 24 hours between coats of Osmo Polyx Oil Raw or Fiddes Hard Wax Oil Natural.

    When applying the wood preservative, the colour of the wood will darken, giving a damp appearance, but will return to its natural look when the preservative has fully dried. The Polyx Oil Raw or Fiddes Hard Wax Oil should be applied thinly to keep the wood looking similar to the natural sanded look when dry.

    Wax Polishes can be used in these environments but is easily marked and stained by water splashes and spillages. We always recommend Polyx Oils or Hard Wax Oils in bathroom and kitchen areas in stead of waxes.

    Always do a test area before starting the main project and follow the instructions on the tin.

  14. Becca Says:

    I will do what you recommend.

    You are so generous with your time and your expertise! Thank you!

  15. Nicky Bramble Says:

    Hi, I wonder if you can offer some advice on looking after a huge, heavy, very old door made of oak?
    The door now hangs inside, opposite a large window, and has done for at least one hundred years, but it may have been used externally before that. It is several hundred years old and has not been touched for a long, long time – it looks dried out and uncared for. What would you recommend to care for it but retain it’s character?
    Thank you for any help you can offer.
    Nicky

  16. nick Says:

    Hi Nicky,

    Sounds Amazing. We would recommend Manns Liquid Beeswax Polish in this type of situation. This product comes as a custard/liquid beeswax consistency at normal room temperature, is easily applied with a brush, cloth or roller and dries within 15 minutes if applied as a thin coat. This will help to feed the wood and can be buffed if desired to produce a sheen.

    If your Oak door is exceptionally dry, it may take several thin applications over time for the wax to penetrate in to the timber of the door. The great thing with Manns Liquid Beeswax Polish is that it will not change the colour of the door.

    Always do a test area before embarking on any project to make sure that you’re happy with the results that the product gives.

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