Painting for wood and wood-based materials processors can be a business in itself

Objects made of wood or derived materials often need finishing. That is to say grinding, staining - if necessary - and final protection with different materials. The choice of materials is made according to aesthetic and strength requirements. It uses oil or wax, for a natural look or varnishes and paints when film strengths, appearance with mirror gloss or other special effects are important. Whichever material you choose, it depends on its application that the final look is pleasing. This can be achieved if the technologies are followed, and the working space and equipment used are appropriate. Without minimum application conditions, no matter how good the products are, they will not make perfect surfaces. In this case, it is better to turn to firms specialising in industrial painting, which have good conditions and high-performance equipment. The fashion for high-gloss finishes has led to the emergence of such a business, but there is still plenty of room for those interested.

Varnishing and painting wood - a business in itself

The idea of making wood varnishing or painting a business in itself is not new. It is a specialisation that guarantees a very good quality of the finished product. There are well-known companies that have been finishing furniture of very high quality for many years and exporting it to countries in Europe, the USA and the Middle East. However, the wooden pieces are made by other manufacturers only up to the finishing stage. The furniture is bought 'blank', i.e. unfinished. Finishing is done by the furniture exporter, who has control over the final quality of the products.

However, painting can also be done as a service for the furniture manufacturer. In this case, the furniture or just parts of it are taken to the industrial painting plant, which finishes them in the best possible conditions and then hands them over to the manufacturer. This is a service that has been around for some time and is used by many of those who make MDF furniture with mirror gloss, a demanding finish that requires special conditions. It is a similar model to car paint shops, where investment in equipment is very important.

Conditions for a perfect finish

But why is it so hard to get a quality finish? What conditions need to be met for a varnished or painted surface to look great? The most commonly used way of applying products is by spraying, so I will now look at the conditions required for this.

Praful is the number one enemy of finishing. In general, the materials used are liquid when applied. By the time it dries, dust and fine lacquer particles that constitute overspray fall onto the finished surface and remain in the film. The result is a rough finish with an altered gloss, very unpleasant in appearance. To avoid such problems, a very good exhaust system and other dust-attracting fittings (water curtains, water baths in the floor) must be in place.

Temperature and humidity in the workspace influences the appearance of the film. The recommendation of varnish and paint manufacturers is to apply products at 18-20°C. If it is too cold, the varnish will not spread well. If it is too hot, the viscosity decreases and the product may leak. High humidity in the workshop can lead to opalescent surfaces or influence drying time.

Equipment with which the spraying is done is also important. In order to get a quality film the lacquer must be evenly spread, not streaked, and there must not be a large amount of overspray. For such a result quality spray guns must be used.

Exhaustion quality. Through the exhaustion process, the stale air (with dust and varnish vapours) is removed from the enclosure and a clean air is introduced inside. The sooner the varnish dust is removed, the less likely it is to get on the film. The air circulation must be calculated so that no 'waves' are created on the varnished surface.

How to get the right conditions for finishing

The easiest way is to have a spray booth which removes stale air with a fan. The air is passed through filters that trap dust and fine varnish particles. The filters can be dry or wet. A dry filter is an agglomeration of fibres through which air is forced to pass. Some of the dry varnish particles and dust will be trapped by these fibres. Before being released into the atmosphere, the air can pass through several such filters, becoming cleaner and cleaner. A water filter is actually a water curtain. The foul air is absorbed through the water curtain, with impurities remaining in the water.

The best conditions for quality spraying are in pressurised spray booths. The pressurised cabin is an enclosure in which a slight overpressure is created by introducing more air than is taken out. As a result, dust from outside does not get inside. For the overpressure to persist the cabin must be very well sealed. The cabin is also equipped with equipment to maintain constant temperature and humidity.

Spray guns play an important role in achieving quality surfaces

Spray guns can influence the final film quality. The more material transfer on the surface is better the better the film looks. Low transfer means high losses, i.e. varnish dust which negatively influences the quality of the film. The types of spray guns with the lowest losses are:

• HVLP
• electrostatic guns
• airless guns

HVLP guns are modified so that the material can be sprayed at low pressure. Only low viscosity materials can be applied this way. Productivity is low, however, and the gun is suitable for occasional finishing and low volume work.

When applying with electrostatic guns consumption is reduced by 50 to 80% compared to conventional spraying. Due to the electric charge, particles are attracted to the object to be finished and only a small amount is lost.

Airless guns use high pressure to make quality applications. The jet of material is forced through a special nozzle that atomises the lacquer which then comes out unmixed with air. It is a good material transfer system, very suitable for viscous materials.

Guns that combine low losses with very good surface quality are those using spray systems of medium pressure. Airmix is such a system, trademarked Sames Kremlin. The concept is a successful one, transforming an ordinary technology into a worldwide industry standard.

When the object of activity is industrial painting, the choice of gun is related to the workload and the type of materials applied. As spraying is supposed to be done at least 8 hours/day and different materials can be applied, a reliable, resistant, flexible and low-loss gun should be chosen. Flexibility helps to ensure that switching from less viscous to viscous material is not a problem. If both solvent and water-based products are applied, it is best to use guns dedicated to each category to avoid high consumption of washing solvents and defects arising from mixing the two types of material.

You can make painting a business. It's not simple, but there are many who are looking for such a service and in the end, it can be a good business.