Some tips for a quality finish

From the very beginning we have constantly presented topics related to finishing. About finishing defects and how they can be avoided, how to apply the finishing materials for best results, how to do the white sanding to avoid defects during finishing, drying, storage, storage and packaging. They all had recommendations on how to do the operation in the best possible way to achieve a quality finish. I thought I would put all these recommendations together. They are equally for those who work in the factory, but also for woodworking enthusiasts.

Preparing for finishing

You have a few things to do before you start work:

• You need to know the characteristics and how to work with finishing materials. Make sure you have the products' technical and safety data sheets, work instructions and technologies.
• Check they are exactly what it says on the label and what you ordered.
• Check the color, if any, and compare it to the sample or the color in the previous packaging. Store-bought materials have all instructions and information on the label.
• The equipment used must be checked before starting work. It shall be washed and cleaned each time after work is completed. The finishing area must be kept clean and tidy. This avoids the danger of accidents during the application of materials.
• The wooden support must be thoroughly sanded before finishing. The more time wasted in sanding white, the lower the risk of finish defects. Sanding is done in several grits, starting from coarse sandpaper to the finest. Sanding is also intended to clean the wood of any stains from adhesives, grease or silicone. If sanding is not sufficient, the wood is wiped with thinner. After sanding, the objects are cleaned of dust in order to remove as little as possible in the finishing area.

Preparing finishing materials

Finishing materials should be thoroughly mixed in the original packaging before use as pigments or other additives may settle to the bottom of the can during storage. Insufficient mixing may result in differences in color or gloss. After mixing, a relaxation time is needed to remove air bubbles.

When using A+B hardenable finishing materials, the amount of hardener added must be in accordance with the data sheet or work instructions. Otherwise problems can occur; too much hardener can result in a brittle film, too little hardener increases drying time and the resulting film is softer.

The mixture between the base product and the hardener has a pot-life. After this time the mixture should not be used even if it is still liquid because it loses its properties. Pot-life can last from 2 hours to several days. Long pot-life products can also be used the next day. In this case it is advisable to mix the old material with the newly prepared material in a ratio of 1:2. Label with the product name, code and date so that you do not forget when the material was prepared. Keep the products covered.

The thinner is very important and should be chosen as indicated. It influences the drying time, film appearance and gloss. The choice of thinner depends on the finishing materials used, the technology adopted and the working conditions (temperature, humidity).

Material viscosity is a very important property in finishing. It is found in the data sheets and its value is determined at 20 grd.C. Viscosity is dependent on ambient temperature. If the application is made with a molding machine or with a valve, the viscosity must be checked and adjusted, if necessary, at the beginning of the work, after each refueling and from hour to hour. The viscosity shall be measured with viscosity measuring cups (FORD or DIN).

During finishing, the temperature of the product, the environment and the wood substrate must be above 15 degrees Celsius. If there are large differences between them, problems of adhesion to the substrate or varnish (orange peel) can occur.

Finishing mode

Pay attention to the number of coats that can be applied. If more than one coat is applied, there is a danger that the varnish film will crack. Apply more than the recommended number of coats only when repairing defects. It is better to completely remove the varnish film and refinish the finish than to be unable to control the film thickness.

As the finish is made of several layers, adhesion between the layers is very important. For good adhesion the intermediate layers must be sanded. Sanding is especially important for catalyzed products.

If products are dried in drying tunnels, items should be brought to room temperature before storage. Panels finished with normal materials (not UV) should not be stacked until after 24 hours to avoid sticking together. Packaging should also not be done immediately after finishing as prints may appear in the film.

I'll stop here with the recommendations for a quality finish. However, I already know that the list needs to be improved, so a revised and added edition.