Guide One – Wood Preparation
The old adage that preparation is everything really applies within the field of woodcare and in this guide Sean Thompson, from Sadolin Technical Services, shows why the start of any woodcare application sets the foundations for success.
Preparing New Wood
It is very important to make sure that wood is properly prepared because, whilst the timber may look clean, it usually isn’t – nor is it suitably ready to receive woodcare products.
To ensure the woodcare coatings that are going to be applied will adhere properly – and therefore give the desired durability – preparation is key. This guide – number one of seven in the This Is Sadolin series – goes through the main points to consider.
Preparing Bare Timber
The first and most important step is to sand down the surface – a very light abrasion is recommended. Sandpaper is ideal and a P180 or a P240 grade is great. Whilst using sandpaper, abrade in the direction of the grain, rather than across it. This is to ensure that marks don’t get left that could be potentially visible when a translucent wood stain is applied. Make sure any imperfections on the surface are removed. Sandpaper also prepares the surface so that it has an ideal key. This means if the timber surface is too smooth prior to coating, the situation is put right.
The next step, which is often forgotten, is dusting off. Again, the timber may look clean but there is a lot of dust. To dust off wood, a rag can be used, but I prefer to use a brush. The important thing is to make sure that you brush across the grain, as well as up and down. This may seem time consuming but it will provide a better finish and the process ensures that the coatings do adhere to the surface and not to the dust.
The final step is to degrease, or clean, the surface. Irrespective of the surface, whether it’s softwood or a hardwood, I recommend it is cleaned down with methylated spirits using a clean, lint-free cloth, whilst wearing gloves. When preparing timbers such as teak or oak, remember they can contain high oil/resin contents or they may contain very high levels of extractives. It is important dirt and grime is removed from the surface prior to coating, otherwise that could cause a problem with adhesion, so put some methylated spirits onto a cloth and then give this a wipe down. The important thing is to rotate the cloth around. I don’t recommend using white spirit. It’s fine for cleaning out brushes, but when using solvent-based systems, it can leave a greasy residue on timber, so methylated spirits is better. For very oily, durable timbers cellulose thinners may be necessary.
When this has finished, the timber is now ready for decorating.
Preparing a Previous Coating In Good Or Bad Order
In Good Order:
When preparing a surface that has already got a previous coating system, often the requirement is only for a maintenance coat. If it is known the wood care product used previously was a Sadolin system, then they are designed to naturally erode. If the surface is in good order, then all that is required is to do a simple clean with warm water and a mild detergent, followed by a rinse off with clean water. Once that is dry, then the surface is ready for decorating.
In Poor Order:
If it’s a system that is in poor order, then consideration needs to be made as to whether it is good enough to put another system over the top. If the previous coating needs to be removed, then the wood needs to get back to clean, dry, sound, bright timber. How to achieve this varies, it can be a combination of a scraper and sandpaper, or even a chemical stripper. However, in a lot of cases a mechanical sander is needed to get the timber back to square one. Once achieved, then proceed to treat the wood as if it is a bare, new piece of timber.
We have a couple of tips for the application of Sadolin;
• We recommend the use of a quality synthetic brush. Use a natural bristle brush with solvent-based items and a synthetic brush for water-based items. A quality synthetic brush for both types of product is ideal.
• When stirring product, always use a broad bladed, flat stirrer. One with additional holes in is ideal for stirring wood stains. The idea is that it’s just like a cake mixture. In the process of stirring the product in the can, all of the ingredients are being lifted and evenly distributed ensuring a nice, even finish.
Applying a Preservative Treatment
Most timbers are actually supplied pre-treated, such as timber joinery i.e. windows and doors. However, Sadolin has a variety of products to preserve wood, which may be required if;
• The timber has been cut and there is an end grain or an end piece that is exposed without any preservative treatment
• The timber is non-durable
• The timber needs to have a preservative treatment
With a piece of timber the face grain is always the bit that we look at. However, the most exposed, vulnerable part is the end grain. It’s particularly important that this end grain area is protected.
Take for example a typical piece of timber decking. It will probably have the green tanalised pre-preservative treatment that’s actually been pressure-treated into the timber. However, cut the timber in half, then that would be an exposed area. Ideally, that should have some preservative treatment brush-applied onto it to help extend the life of the timber. The preservative prevents rot, decay and fungal infestation – and Sadolin has three systems to offer the necessary protection. These are Sadolin Quick Drying Wood Preserver, a water-based system, and the solvent-based systems Sadolin Wood Preserver and Sadolin Ultimate Wood Preserver.
If in doubt about the use of a preservative, then remember it cannot hurt the wood, irrespective of whether it is a non-durable or durable timber. However, it must only be put onto bare timber.
In a situation where top coats are being applied and those top coats are water-based, then it is best to use a water-based preservative. If the top coat is going to be solvent-based, then it is best to use a solvent-based preservative to avoid any confusion.
Sadolin has two products in the range to assist if minor repairs are needed – Sadolin Woodfiller and Sadolin Stainable Woodfiller.
For nail holes or little indentations within the timber then Sadolin Woodfiller can be used to fill in the small repairs. The key is to pick the colour that compliments the shade of the timber, or the colour of the wood stain. For example, if it was a mahogany-coloured wood then choose a mahogany colour.
If it is a medium-sized repair, then use Sadolin Stainable Woodfiller. The use of masking tape allows the actual filler to be applied slightly proud, so when it is sanded down it achieves the effect of looking flushed with the timber. The masking tape also prevents an unwanted ’halo’ effect where the surrounding sound timber surface would be filled unnecessarily.
The Stainable Woodfiller contains wood pulp which will help matching when applying a wood stain or a wood dye, to even everything out.
If everything is followed correctly, then a clean surface that’s properly prepared should be achieved. This will provide a suitable surface to give the coatings being applied the maximum opportunity to bond well and perform.
If these steps are not followed then the end result could potentially cause the coatings to fail prematurely, causing peeling and flaking and moisture to enter the gaps and damage the timber. Sadolin’s systems are designed to avoid peeling or flaking but like any quality system are still reliant on being applied onto a clean, sound, dry surface.
Ultimately, if everything is done correctly then we have a simple maintenance regime whereby the coatings perform, they naturally erode and weather. A quick clean and reapplication of another coat is all that is then required, between every four to eight years, depending on what system has been specified.
Preparation is covered in-depth in the first in a series of seven videos from Sadolin, developed to help specifiers and decorating professionals make the most of the premium woodcare brand’s product range.
‘This is Sadolin’ is a series of seven films, all designed to inform professionals working with wood on a variety of related topics.
The series starts with a film entitled ‘Preparation is Everything,’ now available to view on the Sadolin Woodcare YouTube channel at YouTube
This ten-minute film shows how to prepare timber correctly in order to get the best possible outcome for wood protection.
Want to know more? Please call the Sadolin Woodcare Advice Centre on 0330 0240298