Shop Our Oak Range
Small cracks, often called checks, can appear as the timber dries out and adjusts to changing conditions. These are common in solid oak and are usually cosmetic.
Surface Cracks and Splits
Oak contains natural tannins. When tannins come into contact with moisture or certain metals, darker staining or black marks can develop. This is a natural reaction and can often be reduced or prevented with the correct treatment and installation methods.
Black Markings or Staining
Fresh oak will naturally mellow over time, often shifting from a lighter golden tone to a more silvery or deeper aged appearance depending on where it is used.
Colour Changes
As with all natural timber, oak can move slightly as humidity levels rise and fall. Correct storage and installation help reduce this.
Movement and Warping
Recommended Finishes for Outdoor Oak
Outdoor oak furniture can be cared for in two main ways, depending on whether you want to maintain the original warm colour or allow the timber to age naturally.
Natural Weathering
Oak can be left untreated to develop a natural silver-grey patina over time. This colour change is caused by sunlight, UV exposure, and weathering, and is completely natural.
Leaving your oak untreated will not affect its strength or durability, it will simply develop a soft, weathered look that many owners find beautiful.
Maintaining the Original Colour
If you prefer to keep the golden oak tone, we recommend using a UV-protective exterior hardwood oil from OSMO. This type of oil nourishes the timber, helps repel moisture, and slows the natural greying process.
How to apply:
- Clean the furniture and ensure it is dry
- Apply a thin, even coat of exterior hardwood oil
- Reapply once or twice a year, especially in sunny or exposed locations
Regular oiling preserves the natural warmth of oak while still allowing the wood to breathe and remain stable.
Removing Black Stains From Oak
If black marks have already appeared on the surface of the oak, they can often be treated and reduced. These stains are typically caused by a reaction between the natural tannins in oak and moisture or metal. A commonly used solution is an oxalic acid based cleaner, which is specifically designed to lift tannin stains from timber.
How It Works: Oxalic acid helps neutralise and remove the dark staining without damaging the natural grain of the wood when used correctly.
How To Use:
- Lightly sand the affected area if required
- Apply the oxalic acid solution as directed by the manufacturer
- Allow it to sit for the recommended time
- Rinse thoroughly with clean water
- Allow the timber to dry fully before applying any further treatment
Oak is a natural product, not a manufactured imitation.
One of the biggest advantages of real oak is its authenticity. Knots, grain variation, small splits, tannin marks and colour changes are all part of what makes each piece unique.
If you are looking for perfectly uniform surfaces with no movement or variation, a natural timber product may not be the right fit. If you want genuine character, long term durability and a traditional finish, oak remains one of the best materials available.
Frequently asked questions
Are black marks on oak normal?
Black marks can occur when oak tannins react with moisture and metal. This is a known characteristic of oak and is often preventable with proper installation and suitable fixings.
Are cracks in oak a fault?
Not usually. Small cracks and surface checks are a natural part of the drying and ageing process in solid oak timber.
Will oak change colour over time?
Yes. Oak naturally matures and its colour will shift over time depending on light exposure and weather conditions.
How do I keep oak looking good?
Regular cleaning, suitable treatment, correct storage and appropriate fixings all help maintain the appearance and performance of oak.
Can oak be used outdoors?
Yes, oak is a highly durable timber and is often used externally. Like all natural timber, it benefits from proper installation, ventilation and ongoing care.
Need Help Choosing or Maintaining Oak?
If you are unsure which oak product is right for your project, or want advice on care and treatment, our team is here to help.
Contact Us
