Varnishing Wooden Windows
To obtain long-lasting protection from outside elements for wood and more specifically wooden windows, it is not simply sufficient to be only careful with the process of varnishing windows or with the varnish we choose to use.
There are many other decision-making phases in the construction of outside-facing windows that contribute to obtaining greater durability for the wood. For some time, the main durability problems in the protection of wooden windows have been due to defective designs, protective products not resistant to ultraviolet rays, products not permeable to water vapour, those with little flexibility and little or no protection against xylophagous agents, etc.
Before the final process of varnishing the wood, the following phases must be taken into account:
PRELIMINARY TREATMENT OF WOOD. Covers all actions and work carried out from the cutting of the tree to the mechanization in the carpentry.
Preservation, storage and sanding of wood
NATURE OF THE TYPE OF WOOD. When choosing the type of wood, the following considerations should be taken into account: natural durability, impregnation, extractive substances, knots, specific weight and porousness.
CARPENTRY DESIGN. The edges must be rounded with a minimum curvature radius of 2 mm, in order to obtain a seamless, continuous varnish film. It is also advisable to avoid machining that causes stagnation of water.
CHOOSING AND MAINTAINING THE VARNISH. To protect the wood on the outside, it is best to use primers that contain a portion of pigmentation, as it will help protect the wood and avoid burning the lignin produced by UV rays. A transparent varnishing process causes its protection effect to last less, because the lignin under it burns in 6 months producing stains in wood, and the varnish in this case does not deteriorate. Therefore, it is recommended to always work with colour that in addition to beautifying and protecting the products, are elastic in order to adapt to the contractions and dilatations caused by changes in temperature and let them breathe and avoid condensation of moisture that would affect the formation of white spots on the varnish surface.
To achieve longer durability, we can use the following varnishing process as an example:
1.- Application of Primer with Colour (Walnut, Chestnut, Teka, Dark Walnut…)
For choosing the primer, we will take into account the type of wood (softwood or hardwood) and the choice for the application system (flow coatings, spray gun, household application systems such as brush or roller). As these have been factors in achieving the highest performance and durability in each case, there are three families of primers of natural colours for each case.
700401-410 Esfera Primer by colour / 700231-230 Esfera Softwood Primer by colour / 700251-250 Esfera Hardwood Primer by colour.
The main features of this group of products are: Excellent ability to penetrate the wood (3 mm), high uniformity of colour without the appearance of grey spots and reduced raising of wood grain.
2.- Application of insulating primer and blocking agent for extractive substances.
It homogenises the treated surfaces while maintaining the tonalities of homogeneous woods, reducing the mottling or cracking phenomena seen in softwood. It also acts as an insulator of extractive substances for woods rich in resins or tannins.
Product: 700200 Esfera Primer 0200 Insulator 2K
3.- Application of Base Coating.
Using the base coating, we isolate the wood from external agents, and improve the adhesion between the layers of the varnishing process. Thus, the wood is protected from water, and in hardwoods it moistens the pores of the wood
increasing the durability of the finish. The base coat is applied by spraying, both horizontally and vertically, on the impregnated or the intermediate product, in quantities that vary between 125 and 175 microns of wet film. Usually 2 to 3 layers are applied before applying the finish.
Product: 700261 Esfera Outdoor Base Coating 261 Tixo Universal / 700263 Esfera Outdoor Base Coating
263 Tixo 2K
4.- Application of intermediate products.
Formulated with non-yellowing resins to prevent water absorption and fungal attacks, they improve adhesion between layers to achieve an optimum finish.
The main characteristics of these products are: ensuring that the wood is impermeable. They improve the adhesion between the base coat and finish. They ensure the hermetic impermeability in end grain wood and V grooves, and have an excellent resistance to water.
Products: 700802 Esfera End Grain Sealer 0802 / 700803 Esfera Sealer V 0803
5.- Application of the Finish.
The purpose is to highlight the natural beauty of the wood, while providing the greatest possible resistance to atmospheric elements and the passage of time. It is applied by spray gun, both horizontally and vertically. The finishes are used in quantities ranging from 200 to 300 microns of wet thickness depending on the varnishing system.
Products: 700290 Esfera Outdoor Finish 290 Matte / 700291 Esfera Outdoor Finish 290 Satin.