Varnish for outdoor woodwork is designed to protect products that are used outdoors from negative factors: ultraviolet light, pests, high humidity. Accordingly, the choice and application of compositions should be given special attention, because in stores they are presented in a huge assortment. How to choose and correctly apply wood varnish for outdoor use , we will talk in this article.
Varnish for wood for outdoor use
Today there are many compositions for coating wooden surfaces, but varnishes have one serious advantage - they allow you to preserve the unique and inimitable structure for which this natural material is valued.
The texture of wood is clearly visible through the colored varnish
Paints and varnishes (LKM) are divided according to several criteria, one of which is the conditions, in which wood will be used.
Products that are in the open air are exposed to weather factors, due to which the tree constantly swells and contracts. Varnishes designed for external surfaces form an elastic film on the surface of the material, which allows the wood to withstand regular swelling and drying. Indoor surface treatment compounds do not have a sufficient degree of elasticity, so the film will quickly crack and begin to lag.
It is important to use formulations specifically for outdoor work
Varnishes for outdoor use are used to cover the following elements:
Lacquered facade of the house
Compositions that are intended for such purposes should reliably protect surfaces from negative factors, mechanical damage, and also have good decorative qualities.
In essence, all varnishes are mixtures of substances that are capable of forming a protective film on the surface of the material. To extend the life of wooden products, the composition for outdoor use must have a number of important characteristics.
Terraces need the most wear-resistant varnish
The varnish can dry up to 24 hours or more
Accordingly, it is very important that the ingredients include additives that increase UV resistance.
The wood is exposed to UV rays all year round, therefore the varnish should provide maximum protection.
The varnish must protect the wood from moisture
If the wood has not been previously treated with special substances that protect the material from fire, special attention should be paid to the fire safety of the composition. The same applies to surfaces located in areas with an increased risk of fire, or those operated in high temperature conditions.
Varnishes for exterior woodwork may contain pest-protecting agents, components that give surfaces a glossy sheen or matt finish, and much more.
There are several types of paint and varnish compositions that are used for outdoor woodwork, and each of them has its own characteristics, advantages and disadvantages ..
. The choice of a specific product depends on the characteristics of the material, the operating conditions of the product, as well as the final result that must be obtained.
Oil based outdoor varnish
The basis of such products are refined, thermally processed oils, which give the compositions the necessary properties. The quality of the lacquer coating directly depends on the quality of the base, therefore, it is not recommended to save on products. The second component of such varnishes is synthetic or natural resins, and most of the compounds that are sold in stores contain just synthetics.
The drying time for the compositions is quite long, so it is better to carry out work on clear days at an air temperature above 10 degrees and average humidity.
Important: When applying an oil-based varnish, the wood surface may darken slightly.
Depending on the proportions of resin and oil, formulations are oily, bold and skinny. Exclusively greasy varnishes (2 parts oil and 1 part resin) are used for the treatment of external surfaces, as they are characterized by resistance to weathering.
Features of oil-based varnish
Yacht varnishes and polyurethane varnishes are varieties of such compositions.
The first option is used for surfaces that are in constant contact with water. Yacht (urethane-alkyd) varnish creates an elastic film on the surface that maintains its integrity even when the wood shrinks or expands.
Example of alkyd-urethane yacht varnish
HELO YACHT - urethane- quick-drying alkyd varnish
Important: the application of yacht compositions requires a mandatory priming of the surfaces and accuracy during work. The film that forms on the surface must be solid and dense. If moisture gets under it, the tree will begin to collapse from the inside and the product will lose its original appearance.
Polyurethane compounds are easy to work with , provide high quality coating even if the master does not have the appropriate skills They dry quickly and protect the surface well from abrasion, mechanical damage and ultraviolet radiation.
Polyurethane varnish for wood
Compounds based on alkyd resins and a solvent provide a stable, durable and reliable coating of products. It is not affected by household chemicals, so the surface can be cleaned by any means. The disadvantages of solvent-based varnishes include a long drying time (about 24 hours) and the ability to change the color of the wood - after processing, the material becomes yellowish. The most common alkyd varnishes are GF-166 and GF-177.
Varnish GF-166. The base of the composition is an alkyd glyphthal resin modified with natural oils, with the addition of an organic solvent and substances that accelerate drying. Forms a transparent glossy film on the surface of the products, the drying time of one layer is 48 hours.
Varnish GF-177. In composition and main characteristics, the varnish is identical to GF-166, but has a shorter drying time and requires careful preparation for work.
This type of composition is made on the basis of an aqueous dispersion (for example, acrylic) with a small amount of solvent. Thanks to this, they do not have a pungent smell and do not give off toxic fumes, and work can be carried out even indoors.Water-based varnishes have a wide variety of color palettes and can give the material any chosen shade without masking the unique structure of the wood. Surfaces treated with such compositions are not affected by fungi, mold and microorganisms, and have an attractive appearance.
Eco-friendly, colorless water-based varnish for wood "Aqua"
Water-based varnishes are divided into two types: they can contain only acrylic (one-component compounds) or acrylic with polyurethane (two-component).
Two-component acrylic-based paints and varnishes have improved performance properties and are not susceptible to negative environmental conditions.
|Varnish type||Composition||Average drying time||Strength|
|Oily||Oil and resin, with an increased amount of resin facilitating quick drying of the composition, but reducing the strength of the coating||24-72 hours||High|
|Yacht (alkyd-urethane)||Alkyd resins, organic solvent, urethanes||2-4 hours||Very high|
|Polyurethane||Base with hardener (two-component), base with hardener and thinner (three-component)||4-12 hours||Very high|
|Alkyd||Alkyd resins, solvents (white spirit, solvent), agents that accelerate drying||Up to 48 hours||High|
|Water||Liquid polymer (acrylic dispersion), ant isseptic, plasticizer||24 hours, but it takes 10-14 days to form a film||Average|
Important: alcohol formulations and nitrovarnishes are not recommended for outdoor use. Alcohol-based varnishes are suitable exclusively for restoration and carpentry work, and nitrovarnish are characterized by low water resistance and are quickly destroyed by ultraviolet radiation.
The following companies are among the most popular manufacturers of paints and varnishes:
Quick-drying varnish TIKKURILA UNICA SUPER
Varnish for wood
Facade before varnishing
Correct varnishing is the key to the reliability and durability of the finish.
The main point that must be taken into account before applying work is that paints and varnishes have some features and application conditions.
Preparing the varnish for work
Test the varnish in advance
The rest of the varnish can be poured into small bottles or cans (so that as little air as possible remains between the surface of the substance and the edge of the container), tightly closed and put in a dark place, the temperature is from 5 to 30 degrees. In such conditions, the composition can be stored for about a year.
Glaze for wood
To correctly determine the amount of paint and varnish mixture that will be needed to process a certain surface area, you need to know the varnish consumption per square meter. This parameter depends on the technical characteristics of the material and the composition itself.
Porous species (ash, walnut, oak, exotic wood) require more varnish consumption, in contrast to non-porous ones, which include maple, birch, aspen, cherry.
For this reason, when carrying out work, a solvent or water is added to the varnish.
The average consumption of the paint and varnish mixture when applying the first layer is a liter per 8-10 sq. M.
, and when applying subsequent ones - a liter per 10-12 sq. m.
The varnish is applied using various tools, mainly with a brush, roller or spray gun. Not only the consumption of the composition, as mentioned above, but also the quality of the coating depends on the choice of the tool.
The cheapest, widespread and affordable option. Most often in stores you can find brushes with natural, mixed or artificial bristles. Natural brushes are best for oil-based paints and varnishes, but when working, you should squeeze out the villi well - they have the ability to pick up and hold varnish, so streaks and irregularities can form on the treated surface. Synthetic brushes provide a smooth surface and are practically not subject to wear. The blended bristles combine the strengths of natural and synthetic, and the brushes are ideal for outdoor use.
The tool is convenient for processing large areas: fences, facades, etc. Rollers for applying varnish are distinguished by the features of the working surface of the tool, the length of the pile and the size. Long pile can be deformed during operation, as a result of which the quality of the coating decreases. Large rollers reduce processing time, but are inferior in terms of convenience, since small rollers create a more uniform and dense film. The best option for outdoor use is a medium-sized tool with a long reinforced pile.
Spray gun "Wagner"
Spray gun or spray gun - the most convenient a tool for painting fences and facades, as it can be used to easily process hard-to-reach places. Spraying makes it possible to create a quality, smooth and uniform coating. Spray guns can have a different tank volume, engine power and performance - the higher these characteristics, the more expensive the unit, but it is not very convenient to work with budget models, as they quickly overheat and turn off.
Painting the facade with a spray gun
For better adhesion of paints and varnishes and the proper quality of the future coating, the surface should be well processed.
If you apply the composition to unprepared wood, the coating will quickly lose its attractive appearance, crack and peel off.
The old coating (if any) must be removed with an emery cloth, trowel or a blow dryer until it is clean and hard.
Removing old paint
If there are cracks or cracks in the wood, they must be removed with a special putty.
Putty can be replaced with a mixture of sawdust and glue
Clean the surface of the product from dust, small debris and sand with sandpaper. If there are grease or resin stains Sanding should be carried out along the grain - this will prevent small fibers from picking up, and the wood will be as smooth as possible.
The surface must dry well before further processing.
Grinding with a grinder with a brush attachment
Primer, or coating of lumber with special compounds, some craftsmen do not consider a mandatory stage of processing, but there are several objective reasons for their use:
The primer composition is selected depending on the characteristics of the material and composition for the final coating. Alkyd primer well emphasizes the structure of wood and increases its wear resistance, water-dispersion compositions do not have a pungent odor and are non-toxic, and shellac ones are recommended for covering poorly dried and damp wood
When choosing a primer taking into account the characteristics of the finish coating, it should be taken into account that for paintwork materials based on polyurethane, it is recommended to choose formulations with a solvent content.
When using water-dispersion paintwork materials, it is best to take an acrylic or water-based primer. For outdoor use, it is recommended to choose formulations that additionally contain components that prevent the appearance of rot, fungus and mold.
The application of the compositions can be started after preparation (the process is described above) and thorough drying of the surface.
Tools for applying the primer
Step 1. Prepare the composition (dilute according to the instructions) and mix well him.
Pour it into a suitable container wide enough to dip your brush into.
Valtti-Pohjuste priming antiseptic for Tikkurila wood
Step 2. Apply the solution to the surface in an even layer by running a brush or roller along the grain of the wood. When processing a facade or a fence, pay special attention to the lower part, as it is most susceptible to moisture.
Applying the first coat
Allow the first coat of primer to dry well.
Step 4. To clean the dried layer with a "sandpaper", if the surface is uneven, use a putty on wood. Remove dust from the wood that has formed after sanding.
Removing dust with a brush
Apply 1-2 more over the first layer, each of them must be allowed to dry well.
Applying the primer
After the primer has dried, proceed to the finishing - coating the product with a varnish mixture.
Impregnation for wood
Before varnishing the wood, it is recommended to carry out an adhesion test. Cover a small area of the prepared surface with the composition, apply the composition, and after 2-3 days try to remove it with a coin or spatula.
If the coating is difficult to remove, then the varnish is well connected to the base. In the case when a coin or a spatula leaves clearly visible, deep marks, it is necessary to process the surface again or choose another varnish.
It is best to apply varnish on a horizontal surface, therefore, if possible, place the product vertically - for example, when processing doors, remove them from their hinges and put them on the trestle.
Step 1. Prepare the composition (if necessary, dilute it with water or white spirit), mix well, pour into a suitable container.
Mixing the varnish
Step 2. Apply the first coat of varnish to the wood. Squeeze the composition onto a tool (brush, roller) slightly to avoid dripping. On horizontal surfaces, the varnish is applied in stripes, and on vertical surfaces - in cross movements, uniform and smooth. Some compounds (for example, acrylics) set almost immediately, so you need to work quickly enough so that no brush marks remain on the surface.
The varnish must be rubbed well and make sure that bubbles do not appear on the surface - they can be removed by brushing along the grain of the wood. When working, pay special attention to hard-to-reach places and corners.
Step 3. After applying the first coat, it must be allowed to dry. The drying time of the varnish differs for each type of composition: in the case of water-based paints and varnishes it is from 1 to 12 hours, for alkyd and polyurethane mixtures - 24 hours, so it is better to clarify it in the instructions for the product.
Step 4. Once the initial coating is dry, it is best to sand it with fine-grained emery - this way the second layer of varnish will adhere well to the first.
Step 5. Apply a second coat of the compound, this time undiluted, and let dry.
Assess the treated surface in good lighting, apply if necessary another 1-2 layers of varnish.
When using quality formulations and the correct application, two coats of varnish are usually sufficient for a good surface finish.
Facade after varnishing
Tinted varnishes usually used to cover inexpensive types of wood.During processing, two tasks can be solved at once: to protect the material from damage and negative factors, and also to "refine" its appearance. The technology for applying such compositions does not differ from the application of conventional ones, but has a number of nuances.
Grinder for processing walls of a wooden house
Some shades of varnish
The facade is painted with tinted varnish
With the correct choice of the type of varnish and following all the rules for its application, you will get absolutely smooth, a well protected and aesthetically pleasing surface that will delight the eye for years to come.
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