How to clean your green oak frame
As we know from the thousands of oak buildings that have stood proud for hundreds of years, oak is undoubtedly a beautiful and durable material to build with. However, transporting it via vehicles and assembling it on the ground with the use of material lifts, telehandlers and cranes in all weathers, can result in the oak becoming marked, water stained and looking worse for wear.
This can be an area of considerable concern for many, however, it needn’t be.
Dark Spots, discolouration and dirt can be easily removed with an oxalic acid and water solution. It’s quick and simple and far less messy than sandblasting.
Cleaning the oak with an oxalic acid and water solution, unlike sandblasting, won’t burr the surface of the oak. It also doesn’t require bringing in a specialist firm, as it can be carried out by you, if you fancy having a go at doing it yourself.
So what type of stains are most likely to appear on your green oak frame?
Common types of staining
- Irregular light and dark surface staining. This is caused by water stagnation and the leeching out of tannins in the oak.
- Dark blue irregular surface stains. These are caused by iron ions from tools and equipment coming into contact with tannins in the oak and causing a reaction between iron and tannins.
- Grubby marks. These can be caused by processes in the workshop, such as pencil-lines and ink marks left during manufacture. Also, mud and dirt deposits from the building site can make the oak appear dirty.
What is Oxalic Acid?
Oxalic acid is supplied in crystal form, (it looks just like sugar) and is diluted in either water or methylated spirits.*
How to create the solution to clean your green oak frame
In a clean container mix the Oxalic acid with water, as you would mix sugar in tea. Add the crystals to the water (approximately 60g to a litre of water or 4 tablespoons to 1 pint of water) stirring until there is a little undissolved sediment floating around the bottom. This indicates that the solution is now saturated and the saturated solution is ready to use.
One kilo of oxalic acid will make approx 9 litres of ready-to-use solution, with an approximate coverage of 12 sq meter per litre (depending on porosity of the timber)
Note: Adding more Oxalic acid crystals will NOT make the solution any stronger.
You can use Methylated Spirits instead of water.
Using Methylated spirits allows for quicker drying, enabling a protective coating to be applied to the timber sooner. But take care not breathe the fumes.
How to apply the solution
Apply the solution evenly, to the entire surface of the oak with a cloth, sponge or brush, working it into heavily stained areas.
Spot treating an individual area will create an uneven patchy appearance; therefore, areas with heavy staining may require spot treating first, with a further application to the entire surface after.
Note: coatings, such as wood stain, paint, wood oils etc. will prevent the oxalic acid solution from working, so all protective coatings will need to be removed first.
The Oxalic acid solution should remove the stains within 20-30 minutes. However, the bleaching process will continue for 1 – 2 hours.
If staining still remains, apply more solution to the stained area only. Continue until the desired colour is obtained; it may require multiple applications to fully remove all the staining.
To neutralise the bleaching action (stop bleaching), wash the surface with clean water or methylated spirits and wipe dry with a clean, lint- free cloth. Water will raise the grain of the wood, so allow wood to dry fully before sanding.
Note: When sanding, the raised grain area will appear darker.
*Warning: Always wear suitable gloves, respiratory mask and eye protection (ideally a full face visor) at all times when handling this product.
We hope you’ve found this post on cleaning your green oak frame useful. If you’d like any other advice concerning looking after your oak framed structure or would like to speak with us about building an oak framed extension, send an email to firstname.lastname@example.org — we’d love to hear from you!
Antonio & the team