Video: How To Varnish Parquet Correctly
2023 Author: Douglas Hoggarth | [email protected]. Last modified: 2023-05-24 11:23
The varnishes of the great masters surprised their contemporaries with their purity. Admiring the quality of the varnish, they said: "As transparent as a baby's tear." Unfortunately, the compositions of the varnishes of the masters of the 18th-19th centuries. Irretrievably lost: they were kept secret, and the master trusted the secret of their preparation only to the best and most trusted student.
No matter how hard scientists tried to reveal the secret of the Stradivarius varnish, no one was able to recreate it. One can safely assume that the quality of the old varnish depended on its organic ingredients.
Modern parquet varnishes: their properties
When choosing a varnish (usually a varnish for parquet works is chosen by their performer - master parquet flooring, taking into account the wishes of the customer), it is necessary to take into account its most important technical characteristics, which are usually given in the description. The determining factor when choosing a varnish is the purpose of the room and the expected load on the parquet floor. If the room will be used by a small number of people, and they will walk in light indoor shoes, then you should choose a floor varnish with a normal load. For non-residential premises where people actively walk in outdoor shoes, floor varnishes with increased load are recommended.
In non-residential premises with high traffic (bars, restaurants, museums, shops, etc.), it is preferable to rub them with water-repellent compounds - oil impregnations or wax mastics instead of varnishing parquet floors. Thanks to this, the useful layer of the parquet plank remains in good condition for a long time, since when rubbed with oil or wax, the parquet is not sanded, as when varnished. (For example, the parquet floor at the Ostankino Museum, which is a work of art, has been preserved in good condition for more than 100 years thanks to the constantly renewed wax coating.)
Varnishes are distinguished by:
chemical composition: water-soluble, based on artificial oil resins (alkyd and urethane alkyd), anhydrous polyurethane (DD, PUR-varnishes), acid-cured or formaldehyde resin-based (SH-varnishes), primers;
technological properties (for example, by the method of application, viscosity, flowability);
resistance to operational loads (i.e. resistance to mechanical stress, external environments, light) and service life;
qualities that affect the appearance (for example, the ability to paint wood, i.e., the degree of purification from turbid impurities, transparency);
degree of gloss: matt, silky-matt, semi-matt, semi-gloss, glossy;
the degree of harmlessness to the environment and the possibilities of disposal.
With the advent of tinting technology, there are practically no restrictions in the selection of the color of parquet varnish, and colorless varnishes are a thing of the past. Customers and performers of parquet works have ample opportunities for interior renovation, because after 3-4 years the customer can change the color of the varnish to a fundamentally different one, while choosing from more than 2000 shades. On average, varnish consumption when applied in one layer is 8-10 m2 / l. However, the parquet floor is covered with at least three layers, excluding the primer coat. It is recommended to use a respirator when working with varnishes. The temperature of the floor and air during the application of varnish should be at least 15 and not more than 22 C. Particular attention should be paid to heated floors. The final layer is usually operational after 24 hours. The duration of its exposure before the start of intensive operation is from 3 to 14 days and depends on the temperature of the floor and the environment and the relative humidity in the room. This means that you can walk on the floor within a day after applying the last layer, and bring furniture into the room only after waiting for the final polymerization (for this, a coin test is carried out).
The lacquered parquet floor must be protected from direct sunlight, low air humidity and lack of ventilation. Otherwise, over time, the varnish film will lose its hardness, become soft, pliable, and tears may appear on it. Air humidity in the room should be at least 50% and not higher than 70%, temperature - at least 15 C, air exchange rate - at least 50 l / min. In rooms with a large temperature and humidity difference, it is advisable to use oil or wax mastics. It is advisable to wipe the lacquered parquet with a well wrung out damp cloth. Maintenance of matt and silky-matt varnish is much easier, because when sunlight hits the surface of the film, traces of grease and small scratches are not visible. To remove shoe stains, ink, dirt, grease from semi-mat, semi-gloss and glossy finishes,use special solutions and polishes. It is advisable to stick felt "heels" on the furniture legs in order to reduce the point load on the varnish film. You cannot walk on varnished floors in street shoes, especially in high-heeled shoes - cracks, dents and chips may appear on the parquet floor. The lacquer coating on worn-out areas of the floor must be restored in a timely manner. You cannot attribute waterproofing properties to varnishes - they are only vapor barrier. In the event of a significant excess in the room humidity of the walls (more than 5%) and air (more than 80%) or a serious leak, moisture will sooner or later pass into the parquet, no matter what varnish it is covered with. If moisture accidentally gets on the lacquer strip, then wipe the floor surface as soon as possible with a rag so that water does not have time to penetrate the parquet.
There are varnishes with increased resistance to water and environmental influences. They are intended for covering decks, boats, etc. Their wear depends on the intensity of exposure to moisture and the number of layers of coating.
And now let's move on to a detailed description of the five main groups of varnishes, different in chemical composition.
Water-borne varnishes are in most cases dispersions. The dispersion is formed by small droplets of the binder, evenly distributed over the volume of water. A high-speed stirrer is required to achieve small droplet sizes and even distribution. Water and a binder are poured into a container for preparing a dispersion, then, when emulsifiers are added, all this is mixed at high speed until the mixture stops stratifying. Thereafter, a small amount of solvent is added as a film-forming component. As a result, small droplets of the binder are formed with adjacent particles of emulsifier and solvent, which are surrounded by water. Due to the peculiarities of preparation, water-soluble varnishes dry differently than varnishes with a large amount of solvent. After applying the varnish, water first starts to evaporate. The film-forming component evaporates much more slowly, so its concentration in the dispersion is constantly increasing. When a certain threshold value of the concentration is reached, the film-forming component begins to dissolve the droplets of the binder (as they say, the droplets of the binder "melt"). Only after this does the film-forming component completely evaporate. The varnish film dries and hardens. The varnish film dries and hardens. The varnish film dries and hardens.
Water-borne varnishes have good adhesion properties when applied to wood surfaces and form a viscoelastic film. According to the content of solvents, they are divided into three categories: they do not contain solvents at all, they contain solvents up to 5 and up to 15%.
When storing the varnish, it must not be allowed to freeze. When applying it, the ambient temperature must be higher than the minimum allowable (15 C). Water-based varnish has the negative property of gluing the side joints of parquet films. Its adhesive properties can be reduced by the use of a primer, but cannot be completely eliminated. The positive properties of water-based varnishes include a very low concentration of solvent vapors in the air at the time of application. The smell of such varnish in the room is felt to a lesser extent than when working with anhydrous chemicals, so water-based varnishes can be used in rooms where people who are not involved in this process are at the time of coating. These varnishes are non-flammable, they can be used where, according to construction conditions, the use of varnishes with solvents is impossible due to the danger of fire or explosion. The negative properties of aqueous varnishes include their relatively low wear resistance in comparison with anhydrous polyurethane and acid-curing groups. To increase their wear resistance, manufacturers are forced to add special additives to varnishes. Thus, a polyurethane-acrylic dispersion can become a binder of water-based varnish for floors with a normal load, for floors with increased load - a modified polyurethane dispersion on fatty acids. At the time of application, water-based varnishes are capricious to the room microclimate. A polyurethane acrylic dispersion can become a binder of water-based varnish for floors with normal use, and a modified polyurethane dispersion on fatty acids for floors with increased use. At the time of application, water-based varnishes are capricious to the room microclimate. A polyurethane acrylic dispersion can become a binder of water-based varnish for floors with normal use, and a modified polyurethane dispersion on fatty acids for floors with increased use. At the time of application, water-based varnishes are capricious to the room microclimate.
In order for the polymerization reaction to proceed normally, they require a relatively stable air humidity in the room (at least 50%), and this is not always possible to ensure, especially in winter, when central heating is working, and if there are no humidifiers in the room.
As a rule, water-based varnishes are also demanding on the branded tool - rollers - and do not like to be applied with a swab, spatula, brush. Since these varnishes have a water residue, it is not advisable to cover them without a primer, especially on “nervous” species: beech, hornbeam, pine, merbau, etc. The primer is usually supplied with the varnish by the manufacturer. It helps to protect the edges of the parquet planks from warping (to prevent the formation of torn edges on the parquet plank, the increase in wood fibers).
Varnishes based on artificial oil resins
The binder for varnishes based on artificial oil resins are alkyd resins, which are produced from natural raw materials, for example, from linseed or wood oil. These natural oils allow the varnish to penetrate deeply into the wood.
Polymerization reactions involving products obtained from natural raw materials are very difficult. Simplifying these phenomena, you can imagine the drying process of the varnish layer as follows. After applying alkyd varnish, the solvent first begins to evaporate - white spirit. Only after a significant part of the solvent has evaporated does the chemical polymerization reaction begin. In this case, double chemical bonds in the molecules of monomers are broken, and the latter are combined into polymer chains, which bind to each other and form a spatial network.
The polymerization reaction becomes possible because the alkene resin molecules have double chemical bonds. At the beginning of the reaction, the molecules are next to each other. When the solvent evaporates, oxygen from the air diffuses into the interior first of the liquid and then the glue-like lacquer film and is located between the molecules of the alkyd resin. As a result, the molecules begin to react with each other with an increase in their size. The varnish film first becomes glue-like, and then finally hardens within 8-12 hours at a temperature of 20 C and a relative humidity of 50%. Depending on how much solvent has evaporated, the thickness of the varnish layer also decreases. Alkyd urethane and alkyd varnishes change the natural color of wood, "set fire" the wood, emphasizing its texture and texture. The hardened varnish layer has the form of a corneous film, which is elastic and at the same time non-slip.
There are alkyd varnishes with high and low concentration of white spirit. Less toxic varnishes with a low concentration of thinner. The varnish "sets fire", enhances the natural color of the wood, emphasizes the texture of the fibers.
The positive properties of alkyd varnishes include the fact that they do not have adhesive properties. If, during the application of varnish, it flows into the gap between the parquet planks, then these planks will not stick to each other.
Alkyd varnishes are used mainly when there is no point in hindering the natural process of changing the geometry of individual parquet planks in the room due to strong vibration loads, temperature changes and air humidity: when covering a plank floor, end parquet, parquet laid on a heating screed (floor heating systems), "Floating" floors, parquet from "nerve" rocks, which quickly react to changes in air humidity in the room, floors in gyms, etc.
The disadvantages of alkyd and urethane-alkyd varnishes can be attributed to their special sensitivity to drying conditions at elevated air temperatures (during operation of central heating, lack of ventilation) and the surface to be treated (due to heating by sunlight, floor heating systems, lack of curtains on the windows). Here you can face a big slowdown in the drying process of the varnish. At the same time, an inflow of fresh air must be ensured, since oxygen is needed to cure the varnish. It is necessary to strictly monitor that one layer of varnish is not applied in quantities exceeding 120 g / m2. Excessively thick coats may result in a wrinkled surface. The wear resistance of oil varnishes is considered worse than that of polyurethane, water-based, anhydrous and acidic.
According to the degree of gloss varnishes are matte, silky-matte, semi-matte, glossy.
Anhydrous polyurethane varnishes
These varnishes are distinguished by their extremely high adhesion properties to wood. At the same time, the lacquer film is viscoelastic and has increased resistance to chemicals. Due to these chemical characteristics, polyurethane varnishes are used in rooms subject to particularly heavy loads associated with intensive movement on the floor and chemical influences, for example, drinks, cleaning products.
A distinction is made between one-component and two-component polyurethane varnishes, known as PUR and DD varnishes. These varnishes are classified as aromatic and aromatic-free. They have different bases: acrylic, urethane, solvent based.
First, like all varnishes, they dry physically, that is, due to the volatilization of the solvent. After this, chemical hardening begins, which proceeds in the form of a polyaddition reaction. In this reaction, different molecules that have reactive groups enter into a chemical bond with each other. In the case of polyurethane varnishes, the main component has a reactive OH group, and the curing one has an AMCO group. As a result of the polyaddition reaction in the polyurethane composition, chain molecules are formed that are cross-linked with each other, which leads to the formation of a macromolecule.
At the time of coating and at the stage of curing, the varnish film must be protected from contact with moisture, before starting work, it is necessary to check that the moisture content of the wood does not exceed 10-12%. If the hardener reacts with water, then CO2 is generated as a by-product, which, released in gaseous form, causes air bubbles to form in the film, bubbling foaming of the varnish layer, which leads to coating defects.
Depending on the base, a proprietary thinner is included with the anhydrous varnish. As a rule, these varnishes do not require primers, and the first layer of varnish does not raise the wood fibers. Varnishes are not as capricious to the microclimate of the room as water and alkyd varnishes, they can retain the natural color of wood or "set fire" the surface. They have excellent elasticity, good light and heat resistance, and can be applied to coatings exposed to water and other external environments (bathroom and kitchen furniture, garden furniture, table tops, stairs, railings, doors). Strongly glue the side joints of the planks.
Acid curing varnishes
The most resistant group are acid-curing varnishes, or varnishes based on formaldehyde resins (SN-varnishes). They are recommended for use where special requirements are imposed on the strength of coatings.
Acid-curing varnishes are available in one- and two-component. The latter are mixed with a hardener in a 10: 1 ratio. The hardener contains an acid such as hydrochloric acid or organic acids. Immediately after mixing the varnish and hardener, a catalytic reaction begins. A hardener is needed in it as a catalyst that initiates the onset of the reaction. After applying a layer of varnish, the solvent begins to evaporate from the formed film. The binder molecules react with each other and, decomposing, release formaldehyde as a condensation product. Hence the name of the reaction - polycondensation reaction.
The technical advantages of acid-curing varnishes are their high adhesion properties, low sensitivity to temperature and humidity changes in the room. These varnishes are not capricious to tools: roller, spatula, brushes, tampons, spray guns. Due to the use of urea and formaldehyde resins in the varnish, the wood is painted in light, natural colors. The varnish does not require priming. Strongly glues the side joints of the planks. Alcohols are always used as a solvent for these varnishes, for example, etalon (potato alcohol). Work with acidic varnish in a well-ventilated area. At the time of its application, it is necessary to ensure that there are no people in the adjacent room who are not protected by respirators, since severe irritation of the mucous membranes is possible.
There is a misconception that formaldehyde released from acid-curing varnish remains indoors for a long time. In fact, solvent residues evaporate within three days when ventilated.
Deciding whether or not to use a primer varnish is a very big decision. The use of a primer varnish is necessary in the following cases:
to avoid water residue falling on the surface of the plank, which raises the villi of the tree;
in order to achieve the desired color tone of the wood surface, prevent the plank from "burning";
for isolation of residues of special primers, oil impregnations and wax mastics;
to improve the adhesion of parquet varnishes to the surface of the floor covering;
in order to isolate natural oils of exotic wood species;
to reduce the adhesive effect of the parquet lacquer in the side joints of the plank.
If the primer lacquer layer is not applied in such cases, then when applying the main lacquer layer, adhesion and rupture of the lacquer film at the joints of the strips are possible. Before applying primer varnishes, it is necessary to check whether they are compatible with the base coat and the parquet floor. The possibility of using primer for heavily worn floor areas should be checked experimentally each time.
A nitrocellulose or polyvinyl chloride solution can be used as a base for primer varnishes. A water-based primer is applied under the water-based varnish, the binders of which are compatible. Due to their thixotropic properties, primer lacquers limit the penetration of parquet lacquers into the thickness of the wood. This reduces the consumption of parquet varnishes per square meter of area. Drying of primer lacquers takes place mainly physically by evaporation of the solvent. The duration of drying to the state of technological hardening is much less than that of parquet varnish and ranges from 15-20 minutes to 1-3 hours.
In addition to primers, there are glazing compounds (impregnating varnishes, stains). They are colorless and colored and are designed to protect parquet and other wooden surfaces from biological damage (decay, mold, etc.) and atmospheric influences (changes in temperature, humidity). Colorless primers allow long-term preservation of the natural color of wood, and are also used to lighten color compositions and pre-impregnate wooden surfaces before applying parquet varnish. Professional parquet varnishes may or may not need primers. The need to use primers depends on many factors that the parquet flooring must take into account. In the product datasheet, many varnish manufacturers indicate the types of primers that are compatible with their varnishes.
It is advisable to use a primer and varnish from the same manufacturer. This is due to the varying degrees of cleaning of the varnishes. Thus, the use of a domestic primer under Swedish or German varnish can lead to a deterioration in the transparency of the coating as a whole, which will affect the final perception of the varnish layer.
The primer should be applied to a well-cleaned surface, evenly spreading along the fibers. It is not recommended to apply primer varnishes to the floor surface covered with parquet varnish.
How to avoid defects when varnishing parquet
In accordance with the international norms DIN, the acceptance of the surface of the lacquer film is carried out from the height of a person's height from top to bottom in diffused light. At the same time, one should not kneel down and use artificial sources of illumination (backlight) when assessing the quality.
About 30% of all claims for finished parquet flooring relate to varnishing. It often happens that the customer makes high demands on the lacquer coating, expecting industrial "furniture" quality. This does not take into account that varnishing is performed manually and sometimes in unfavorable conditions of a construction site.
Despite all the efforts of parquet flooring workers, there are no rooms with an absolute absence of dust, such that the smallest dust particles do not settle on the fresh varnish. Individual brush hairs or small inclusions in the lacquer film are permissible and cannot be avoided. The customer needs to treat such insignificant defects with understanding, because they have no effect on the overall durability of the coating. But it goes without saying that these concessions do not apply to significant defects.
The surface should be varnished evenly. However, the requirement for the same thickness of the varnish layer is not valid due to the different absorbency of the wood. The film should not have large roughness, sagging, distinct edges of lacquer stripes, missing areas. The coating should have the same gloss.
So that the final result of the work does not disappoint either you or your customer, before applying the parquet varnish, it is necessary to carefully study the manufacturer's recommendations and accompanying technical documentation, pay attention to the restrictions on the use of the product and the compliance with the shelf life of the technical requirements. If, during the application of the lacquer coating, obvious defects related to the quality of the lacquer are found, stop the work and inform the manufacturer or the seller about the incident. With a trusting relationship between the seller and the buyer, good work results can always be achieved.
The varnish should be applied in strict accordance with the manufacturer's recommendations. You should start applying varnish immediately after finishing sanding the parquet. Currently, the following methods of applying varnish are common: manual (swab, brush, spatula, roller) and mechanical airless spraying with a spray gun. Basically, only the primer or the first coat of varnish is applied with a spatula. Further coats should be applied with a brush or roller. If the varnish is applied with a spatula, then the passages in any case should be oriented crosswise to each other. This means that if the first passage was along the room, then the second should be across. Spatula strokes are usually done in an S-shaped motion. The advantage of this method is that the varnish is more durable. At the same time, the joints of adjacent sections are masked. Since the absorption of varnish into the wood with this method of application is negligible, the wood takes on a light tone.
The varnish brush should be wide. Brush strokes are usually made in a U-shape. As a result, an overlap of the adjacent area is achieved and at the same time no thickening of the lacquer layer is formed. At a time, the varnish must be applied to an area of such a size that the brush is always in contact with the freshly applied edge. After working with two-component varnishes, the brush must be rinsed with a solvent so that the remaining varnish on the brush does not harden. During a break when working with one-component varnishes, the brush can be kept in a container with varnish. This container must be closed during long breaks or transportation.
If the varnish is applied with a roller, the directions of movement during work must always be oriented crosswise. When moving across the varnish is applied, when moving along it is leveled. When leveling, the roller should only perform reciprocating movements, after which it rises, shifts by about 3/4 of its width - and the cycle of reciprocating movements is repeated. Slow down near walls to avoid accidentally touching the wall. When applying varnish with a roller, never make an M-shaped movement. This is due to the danger of shade-like bulges appearing on the varnished surface.
If the roller has been in a bath with varnish for a long time, then before resuming work, it must be thoroughly rolled out, since otherwise dripping is possible when applying varnish.
Let's take a look at the causes and ways to prevent common varnish defects.
The varnish layer does not dry
substances contained in wood (natural oils) prevent the varnish from hardening. For example, varnish based on artificial oil resins (urethane-alkyd, alkyd) does not dry on wood of some exotic species (olive, teak, gum);
the surface is poorly sanded, the remnants of wax mastics are preserved in the old floor coverings and prevent the hardening of the varnish layer. This can happen, for example, when using polyurethane anhydrous, acidic, urethane alkyd and alkyd varnishes;
the hardener was added to the two-component varnish in an insufficient amount, not mixed or poorly mixed, or not applied at all;
too low room temperature (below 10 C);
the room temperature is high enough, but the floor surface is cold;
insufficient access to fresh air (lack of ventilation);
incorrect selection of hardener, for example, instead of an acid hardener, a hardener for polyurethane varnish was added to the varnish.
if the slowdown in the hardening process of the varnish is associated with substances contained in the wood or too low a room temperature, then in most cases it is sufficient to increase the temperature to 20 C and increase the ventilation. After a while, the hardening process is activated again and the varnish dries up;
if an inappropriate hardener was used or it was applied in an insufficient amount, then in most cases it is necessary to sand the applied coating;
In some cases, when using acidic varnishes, the situation can be corrected by applying a clean acidic hardener with a brush to the surface of the uncured varnish. But after such an operation, it is necessary to re-polish the lacquer layer.
the varnish was applied too cold;
the temperature of the floor surface is too low, the air humidity is too high;
the total humidity in the room is too high (it happens in new buildings).
Whitish beads always indicate that moisture from the air has condensed on the freshly applied varnish. In most cases, solvent treatment of whitish beads helps. Always re-varnish after this. Before applying the next layer, it is necessary to warm up the room and it is especially important to increase the temperature of the floor surface.
Swelling of the varnish layer. Exfoliation
incompatibility of varnish layers due to different chemical composition. For example, a top coat of a two-component polyurethane varnish is applied to a layer of water-based varnish;
wrong choice of thinner;
the varnish application tool is impregnated with a cleaning agent and, during application, the varnish has mixed with this agent or the tool is poorly cleaned;
insufficient intermediate grinding.
- when swelling in small areas, sanding and applying a new layer is possible; when swelling over the entire surface, the situation can only be corrected by completely grinding the applied varnish.
the varnish is too cold;
the varnish layer is too thick;
exposure to sunlight;
incorrect selection of a roller or brush for applying varnish.
Bubbles are formed when the lacquer layer hardens only on the surface, but remains liquid inside. The evaporating and rising solvent cannot penetrate the hardened film and accumulates in the form of bubbles. The situation can be corrected only by polishing the film surface and reapplying a layer of varnish.
too high room temperature or high floor temperature;
the layer of the applied varnish is too thick;
the pace of work is too low, the areas covered with varnish have time to dry before the adjacent area is covered, and there is no adhesion between adjacent films;
inaccuracy in work or incorrect selection of a tool for applying varnish.
the viscosity of all varnishes, which means their technological properties, including adhesion, can be slightly improved by adding thinners;
when applying the first layer, the absorbent component is always higher than when covering the remaining layers of varnish. When applying the second and subsequent layers, it is advisable to add a small amount of solvent to the varnish in order to improve adhesion to the previous film;
in most cases, it is enough to change the rhythm of work so that neighboring areas are varnished as quickly as possible and do not have time to dry;
to reduce the speed of drying of the film, a decrease in heating and a decrease in the intensity of ventilation helps.
the varnish tool is out of order; this especially applies to rollers;
wrong choice of thinner;
the applied varnish is too cold;
"Silicone poisoning" of the varnish surface.
In draft conditions on site, many parquet varnishes are prone to crater formation, especially if the varnish to be applied has been overcooled during storage and has become overly viscous as a result. The situation can be corrected by carrying out a complete intermediate polishing of the face layer. The polished film is then sanded with a sharp-edged metal spatula. After filling, the surface dries well, but it should no longer be sanded; then a new layer of varnish is applied.
In most cases it is very difficult to give an exact definition of the concept of "roughness", since the roughness parameters are often not well known.
very fine bubbles are distributed over the film;
the film has got dust;
improper intermediate grinding (polishing) of the varnish;
the remains of the varnish crust from the container for applying varnish fell on the film;
fatty fingerprints on the instrument.
In most cases, it is possible to detect film roughness only by literally armed with a magnifying glass. Most of the claims declared as roughness are related to dirt on the coatings. At the facility, it is necessary to maintain by all means the cleanliness of the working tool and container with varnish.
Wrinkling ("elephant skin")
too early application of new layers of varnish;
too thick layer of applied varnish;
incorrect choice of thinner.
The defect can only be corrected if wrinkles appear in small areas of the coating. If the wrinkling extends to the entire surface of the floor, then the applied layer of varnish must be sanded off. Varnishes based on artificial oil resins are especially prone to wrinkling if they are applied in an excessively thick layer or if a new layer is applied without allowing the previous one to dry sufficiently.
Gloss or haze has a mottled character
Reason: the applied layer is very thick, matting additives settle unevenly in the varnish layer.
Remedy: intermediate polishing and applying a new thin layer of varnish is required.
- large applied layer thickness, for example, in the case of acid-curing varnishes; Too much hardener has been added to the two-component varnish.
A cracked layer of acidic varnish can only be completely sanded off and the surface varnished again.
How to repaint furniture parquet
At present, factory-varnished parquet has appeared on the market. The varnish on such parquet is applied mechanically by airless spraying in special factory vacuum chambers and cured by ultraviolet or electron beam irradiation.
The factory varnishing technology of the parquet eliminates the defects of manual application and allows achieving “furniture” quality. However, sometimes craftsmen are faced with the customer's wish to re-coat such parquet with varnish under the conditions of a construction site in order to hide laying defects (large gaps between the planks) or operation (varnish chips, etc.). In this case, it is necessary to pay attention to the following aspect: not every parquet, varnished in production conditions, can generally be re-varnished. This is due to the fact that bonding varnishes used in industry are not always compatible with manual varnishes.
The problem of compatibility between factory and newly applied varnishes must be investigated in each case. It is best to consult a lacquered parquet dealer as not all commercially available parquet lacquers can be recoated.
Before applying a new layer, it is necessary to sand the factory varnish with a single disc machine so that after polishing the entire surface becomes evenly matt. However, if the base has a local curvature or the bar is warped, then there is a danger of complete removal of the varnish or the preservation of the intact varnish layer in some places (there is a possibility of delamination due to insufficient adhesion).
The next problem is the visual highlighting of the plank joints. When the varnish is applied to the front surface, visually the joints between the strips will be even more noticeable. Even if the gaps in the joints of the planks are so small that a complaint is out of the question, the appearance of the coating may deteriorate greatly and the customer will be dissatisfied.
It should be added that dust particles falling on the freshly applied varnish layer will be clearly visible on the front surface of the film of almost perfect quality, which can be a reason for making claims. After analyzing all this, the conclusion should be drawn: re-varnishing of finished parquet should only be carried out under extreme circumstances.
These recommendations are based on experience and knowledge gained in the manufacturing process. They may not be binding on everyone. The result of your work may differ from that indicated in the article. We hope that our tips will help you achieve good quality.