Why do we finish wood with a protective coat?

Posted on Posted in Furniture Maintenance

Out in nature, our trees need water to grow and form, and they support the surrounding eco-system of insects and fungi. But once transformed into a beautiful piece for the home, water and bugs soon becomes woods’ greatest enemies.

At African Touch, we use the most effective ways to ensure your dream piece can last for generations.

Keep it dry and let it breath

As a naturally porous material, wood is affected by various external conditions, with the most damaging being the natural humidity in the atmosphere – both indoors and outdoors. And that’s before we’ve even mentioned the rain and wind!

Increases in humidity and moisture in the air cause wood to expand and contract, as basic science has taught us. Sometimes, we just don’t realise how the subtle yet damaging changes in conditions can cause extreme damage – your beloved table could literally explode as the wood splits apart through this stress.

The reassuring part, is that this can all be controlled before your product reaches your home in two ways – and with just a littler extra future care on your part for those outdoor pieces.

Designed for movement

The first, lesser know way of reducing the effect of moisture variation is actually in the design.

Design is important to counter the effect of moisture movement into and out of wood, which in turn causes the wood to move. Examples of this are where we have a relatively large flat surface such as a cabinet door or side. If made of a laminated wood panel this would tend to warp, so we make a panel that fits into a frame (imagine your window frame) to allow for natural movement.1. These doors re made up of panels fitted within frames.

Another example is a large tabletop that is secured to the legs with special steel brackets that slot into grooves in the leg rail, allowing the top to expand and contract within the fitting with ease.

2. A large table top fitted to the sub structure with steel brackes in a groove to allow wood movement.

Sealing the deal

The Second, and more commonly known, is to seal the product with a suitable protective coat that slows the rate of moisture movement in and out of the timber.

There are basically 3 types of protective coat used commonly in Southern Africa:

  1. A catalysed lacquer. This is used by furniture manufacturers and sprayed on in a professional spray booth. It provides a very durable, clear finish, but is not suitable for use outdoors or in direct sunlight.3. Applying lacquer
  2. A polyurethane finish. This can be applied by brushing on and gives a clear, durable finish but takes several hours to dry, longer in wet or cold weather. A typical example is Woodoc.
  3. An oil finish. Modern oil finishes are synthetic water repellent oils that are easy to apply by brush and excellent for outdoor furniture, though they are equally suited to indoor. A good example is Satinwood 28 by Timberlife.4. Entrance door with an oil finish

Attacked by nature

The porous nature of wood also means that it can accumulate microscopic dirt, and can be subject to invasion by fungus & bacteria, or attacked by woodborer or other insects.

Borers will eat away at the natural sugars and carbohydrates in the cell tissue of the wood, and again cause the timber structure to collapse.

Fungal attack is what we commonly know as ‘dry rot’. Over time, this can result in the complete collapse of the cell structure of wood. Fungal attack also discolours the timber and spoils the natural beauty of the grin.

Preventing fungal, bacterial and insect attack is a three-phase process and starts with the correct treatment of the timber before a finishing coat is applied. Initially, the timber should be seasoned in kilns – yes, like the ones used to set pottery, but much bigger.

5. Kiln loaded with timber

As part of the drying cycle, the temperature is raised during the last phase to kill off any organisms existing in the wood. We always use properly kiln-dried timber. Once the product is completed, and before the finishing coat is applied, it should be fumigated to destroy any organisms that may have entered in to the wood between the extraction from the kilns, and build completion. Only then do we apply the protective coat as the final preventative measure.

Good quality oil finishes are normally excellent at preventing fungal and insect attack because they will contain a fungicide and insecticide. If you’re topping up your outdoor pieces yourself, it’s always good to check on the packaging that this is the case. Lacquers and varnish are also very effective as they provide a barrier that the organisms cannot cross.

Our Wood Makes the Grain

At The African Touch we use extremely hard and dense timber, Zambezi Teak (a.k.a. Rhodesian Teak). Because of this extreme density, the effects of humidity variations and the degree to which it can be attacked by fungus etc, is greatly reduced. However, we implement all of the recommended preventative measures above. As a result, our products do not have any problems with wood movement or fungal/insect attack.

Protective coats also enhance the natural beauty and grain of the timber, and bring out the wonderful colours found in many timber species. To me, there is no better feeling than when a piece has been carefully hand finished and the first coat of lacquer or oil is applied – it reminds me of an African sunrise in the rainy season as the early light bursts onto the high cloud, reflecting a myriad of wonderful colours!

6. The first coat of lacquer applied revealing beautifyl timber grain

Texture is another factor that can be affected by a protective coat finish. For instance, oil finishes often give a natural feel and appearance to the timber. On the other hand, gloss or semi-gloss lacquer applied in a series of coats and carefully sanded between coats will give a mirror smooth, bright and clear finish – similar to a French polish. A lacquer finish is heat, water, solvent, acid and alkali resistant. It is ideal where you want to completely avoid ‘water rings’ from watermarks or dirt stains and the like.

7. Oil finish gives a natural feel to the timber

Choosing the right protective coat to match your desired look, and your furniture’s needs, is the final piece of your selection process. We’re here to help you navigate the options, and prepare you for any future care.

8. This lacquer finish emphasises the texture of the piece

After all, it’s this final touch that will keep your piece looking fresh and stunningly beautiful for years, provided it is looked after and maintained – but we’ll save that topic for another day!