With varnish you can highlight the natural beauty of wood, while at the same time protecting the surface from external influences. However, in cases where the surface is subjected to heavy loads, it is very important to choose the right composition.
Polyurethane varnish for wood provides a very durable, long-lasting coating without overshadowing the natural beauty. natural wood.
What is polyurethane varnish?
Polyurethane varnish is a protective composition that is suitable for coating wood, fiberboard, chipboard, and other similar materials. It is different from other varnishing compounds high degree of protection.
Thanks to its durability polyurethane varnish reliably protects the surface from impacts, moisture and wind, mold and mildew and other aggressive environmental influences. It can be applied using a brush, roller or spray gun.
Specifications
According to their own physical and chemical properties polyurethane varnish is close to rubber materials, which provides it with greater resistance to impacts and other deforming mechanical influences.
Other peculiarities compositions based on polyurethane:
- hardening time - up to 3 weeks;
- coating durability - at least 10 years;
- heat resistance up to 110°C.
Advantages and disadvantages
In addition to strength and durability benefits polyurethane varnish include:
- good decorative properties;
- high adhesion even to polished surfaces;
- self-extinguishing ability;
- elasticity;
- high resistance to sudden temperature changes;
- resistance to light;
- vibration resistance;
- chemical inertness.
Due to their inertness, polyurethane-based varnish compositions resist the most aggressive chemical agents such as ammonia, acetic, sulfuric, hydrochloric and other acids.
TO shortcomings relate:
- long drying time for some types of polyurethane varnish;
- before using a two-component composition, the base and hardener must be combined and mixed thoroughly;
- after mixing two-component polyurethane varnish ready-made composition suitable for use only for a limited period, which can be up to 12 hours.
Types of polyurethane varnishes
There are one-component and two-component varnishes. The former are sold immediately in a ready-to-use form, and before application they only need to be diluted with a solvent if necessary.
In the case of two-component varnish, sold separately base and hardener, which must be mixed immediately before.
Such mixtures differ from one-component ones in their increased durability, therefore they should be used to cover surfaces and parts designed for use in the most difficult conditions.
Polyurethane varnishes are sold in cans and can be applied with a brush and roller or diluted to the desired consistency and poured into a spray gun.
Polyurethane varnishes in the form of sprays are produced in cans and are immediately ready for application to the surface by spraying.
Depending on the solvent used, there are:
- alkyd varnishes;
- urethane;
- varnishes based on organic solvents;
- polyurethane varnishes for water based.
Color variations
Depending on the appearance , which they give to the surface after drying, polyurethane varnishes are:
- glossy;
- semi-matte;
- matte.
Wood coated with glossy polyurethane varnish looks very attractive, especially if after the composition dries polish it using special pastes. But any defects, such as scratches, will be more visible on this coating.
Therefore, it is undesirable to paint a surface that is subject to mechanical stress with a glossy composition.
In addition, applying glossy varnish so that the surface looks good is more difficult than matte.
There are clear polyurethane-based varnishes and compositions that contain pigments and give the surface certain shade.
Application
Polyurethane varnishes are used to cover surfaces in cases where it is important to obtain a strong and durable coating. They can be painted:
- exterior walls ;
- garden buildings;
- furniture;
- musical instruments;
- parquet;
- stairs;
- yachts.
But polyurethane varnishes are also used for painting other surfaces that are not subject to severe stress - for example, interior walls houses and ceilings.
What is the recipe for wood varnishes?
As hardener for two-component varnishes Isocyanates may be used. Polyisocyanate is a dark brown liquid mixture that contains diphenylmethane diisocyanate, isomers and homologues. Reacting with the base, this composition forms polyurethane.
To obtain a color coating you need use pigments. They must be selected taking into account the solvent that is suitable for the selected varnish.
To make varnish desired color, you can use the tinting services that offer outlets, selling paints and varnishes.
Features of application to the surface
Before applying the two-component varnish, it the ingredients must be mixed thoroughly. To do this, the hardener is introduced in small portions with continuous stirring.
Then the varnish must be kept for a certain time so that air bubbles come out - from 15 minutes to 1 hour depending on the specific composition. The shelf life of the finished mixture can range from 3 to 12 hours.
If it is necessary to apply a multi-layer coating, each subsequent layer must be applied after the previous one has dried “touch-free”. At temperatures around 20°C this means that the interval between coats should be about 2 hours.
Using transparent polyurethane varnish you can get a beautiful mirror surface. To do this, after the applied composition has dried, it must be polished and sand with specialized paste using polishing water.
After coating with polyurethane varnish, the wood is transformed, acquiring an attractive appearance, and at the same time receives strong and durable protection from external influences.
Polyurethane-based compounds can be used to paint surfaces that are subject to heavy loads, such as external walls houses, floors and stairs, as well as internal walls, ceilings and any wooden parts. When applied correctly, this coating enough for ten or more years.
Learn more about polyurethane varnish on an alkyd-urethane base for wood from the video:
Why is polyurethane varnish needed for wood?
Products made from natural wood have enjoyed great success for many years. It is no secret that natural material requires reliable protection, since it is afraid of moisture, is not resistant to technical fluids, and has difficulty resisting natural atmospheric influences and mechanical damage.
For maximum reduction negative consequences, wood products must be processed using various chemical compositions. And polyurethane varnishes are becoming one of the best helpers in this case.
Types of polyurethane varnishes
The most commonly used two-component polyurethane varnish, modern manufacturers They offer exactly this composition.
In the case of one-component polyurethane varnishes, everything is very simple. You don't need any additional preparation to use them. This varnish consists of several independent components. There is an opinion that the use of two-component products is difficult, this is not so. Before applying it to the surface, you will simply need to mix the base and hardener well in certain proportions. The correct proportions are almost always indicated by the manufacturer on the packaging or in the instructions. Therefore, there are no problems.
According to the degree of gloss (gloss), the varnish is divided into:
- glossy;
- matte.
Advantages and benefits
By choosing a polyurethane varnish for natural wood, you get numerous benefits:
polyurethane varnish coating creates reliable protection from negative mechanical influences, dirt, grease, dust;
- varnish increases the service life of any product, even if they are subjected to regular and intense loads. An example is the parquet floor of the hallway;
- polyurethane coating has increased level abrasion resistance;
- a product on which a layer of varnish is applied receives better aesthetic characteristics. Amazingly beautiful and original structure natural material is not hidden by a layer of opaque material, because such varnish is highly transparent;
- elasticity. Thanks to the special consistency, applying polyurethane-based varnish to wood is easy and simple, even if the product has a complex configuration. In case of moderate deformation, cracks will not appear on the treated surface. In addition, the composition has good adhesion and will not peel off.
Terms of use.
Before using polyurethane varnish on wood, you need to carefully prepare the wood surface. To do this, you must rid it of dirt and polish it. The polyurethane varnish itself is applied using a sprayer. Here a lot depends on how large the surface that needs to be treated is. Taking into account the chosen method, the desired consistency of the product is selected. In certain situations, the composition is diluted with a synthetic solvent.
Two-component polyurethane varnish requires compliance own rules. One of the most important things says that it is necessary to observe the proportions when mixing very strictly. If you do not pay attention to the manufacturer's recommendations, which he indicated in the instructions, then as a result the mixture will not harden, crack or fall off. The finished mixture has a limited lifespan; after mixing, the polymerization process occurs. If ready mix If the varnish and solvent dries out, it cannot be diluted; polyurethane varnish is irreversible.
Always prepare as much compound as you need to apply at one time. There is no need to stock up on wood varnish when preparing it for future use.
The number of layers required varies and depends on how it will be used in the future. wood material. But general recommendation The advantage is that you don’t need to skimp on the composition and apply less than two layers. You must wait before applying a new coat. How many? You can find this information in the product instructions. There is no need to refuse to follow the rules.
To mix two-component polyurethane wood varnish, use the special container in which it was sold to you. Make sure that all remnants of the second component fall into the container as close as possible to the first. You can disrupt the correct proportion of the composition if there is a lot of mixture left on the walls and bottom of the jar. An incorrect proportion, in turn, will lead to the fact that all the characteristics and performance properties of the varnish will deteriorate.
Before you apply polyurethane wood varnish, you need to mix it well. Make sure that the temperature in the room during treatment is positive. The drying period of the finishing layer in most cases is approximately 7-8 hours.
How to choose?
Purchase protective compounds for wood processing can always be called an important process. After all, the cost of wood has remained high for many years. If you don’t know how to choose a polyurethane varnish, start from what properties it should have and what qualities are most valuable to you. For example, if you decide to purchase a composition to apply it to the floor, then determine in advance the intensity of future loads. In case of floor covering, which is not intended for large crowds of people, you can choose a polyurethane wood varnish that does not have a high degree of protection. If you want to treat a floor on which “mass gatherings” will be held in the future, and which quite possibly will be constantly and heavily soiled, choose products that have the maximum degree of protection and abrasion resistance.
Any polyurethane varnish for wood has good adhesion. It is resistant to chemicals. But if you want to get the maximum, then choose two-component formulations. They are the ones that stand out for their best strength and elasticity.
If you cannot choose a polyurethane varnish for wood on your own, simply contact the sales consultants of the Europroject-Center company for help. You can also familiarize yourself with the information in the catalog on the website.
However, we would like to say that these products are in any case high-quality and high quality. If you select a product from famous manufacturer Sayerlack, who cares about its reputation, will always achieve the desired results. But if you try to save money, then in this case you can become the owner of low-quality products. Choosing a polyurethane varnish for wood is not as difficult as it might seem at first glance. The cost of products is affordable and low, and therefore savings are simply inappropriate here. The Europroject-Center company offers a wide range of two-component polyurethane varnishes for Sayerlack wood.
The areas of application of solvents and thinners are extensive. By doing repair work We inevitably deal with solvents for varnish, enamel, and paints. In construction, rust and concrete solvents are used. liquid glass, liquid nails, polyurethane foam and other materials. Artists constantly use solvents, and in everyday life they help us remove complex contaminants. Our article will help you understand this big topic so that you can quickly answer the question: which solvent is best to use in each specific case.
Solvent and thinner: what's the difference?
The terms "solvent" and "diluent" are often used interchangeably. However, there is an important difference between them. If we talk in simple language, the solvent interacts directly with the film-forming (hardening) component.
For example, gasoline is a popular solvent for oil paints. It dissolves the binder so it can thin out paint for application and can remove dried paint stains at the same time.
The thinner does not dissolve the substances that form the film, but can only reduce the viscosity of the composition. For example, water dilutes water-based paint well, but it will not be able to wash off dried paint.
Types of solvents
For convenience, we divide all solvents into the following groups:
- Solvents for paint and varnish materials (paints, enamels, varnishes), as well as adhesives and primers
- Solvents building materials (solvents of bitumen, concrete, foam, rubber, rust, etc.)
- Household solvents(stains from oil, grease, tape, etc.)
- Artistic solvents
Solvents for paints and varnishes
Almost all solvents for varnishes, paints and enamels are volatile organic substances with a low boiling point. These properties ensure rapid drying of the compositions after application.
There are solvents:
— homogeneous - based on one substance or a mixture of homogeneous substances (for example, toluene);
- combined - based on several homogeneous solvents in a certain proportion (for example, P-4 = toluene + acetone + butyl acetate).
As a rule, combined ones differ more high efficiency and targeted action.
Using our table, you can easily understand which solvents are used for which paints.
Purpose of solvents
|
Solvent |
Type of paintwork |
|
Homogeneous solvents |
|
|
Solvent (or rather thinner) of acrylic paint, water-based paint and other water-dispersed paints and biting |
|
|
Solvent for oil and bitumen paints, varnishes, enamels |
|
|
Turpentine |
Solvent for oil and alkyd-styrene paints |
|
White Spirit |
Solvent for oil and alkyd paints and enamels (including PF-115, PF-133, PF-266), bitumen mastics, varnish GF-166, primer GF-021 |
|
Solvent (petroleum) |
Solvent for glyphthalic and bituminous varnishes and paints (including melamine alkyd). |
|
Xylene (petroleum) |
Solvent for glyphthalic and bituminous varnishes and paints, epoxy resin. |
|
Solvent for perchlorovinyl paints |
|
|
Combined (registered) solvents |
|
|
Solvent 645 |
Nitrocellulose solvent |
|
Solvent 646 |
Universal solvent for nitro paints, nitro enamels, nitro varnishes general purpose, also epoxy, acrylic, solvent |
|
Solvent 647 |
Solvent for nitro enamels, nitro varnishes for cars |
|
Solvent 649 |
Solvent NTs-132k; GF-570Rk |
|
Solvent 650 |
Automotive enamels solvent NTs-11; GF-570Rk |
|
Solvent 651 |
Oil solvent |
|
Solvent R-4 |
Polyacrylate, perchlorovinyl, coatings with copolymers of vinyl chloride with vinylidene chloride or vinyl acetate |
|
Solvent R-5 |
Perchlorovinyl, polyacrylate, epoxy |
|
Solvent R-6 |
Melamine-formaldehyde, rubber, polyvinyl-butyral |
|
Solvent R-7 |
Dilution of varnish VL-51 |
|
Solvent R-11 |
Perchlorovinyl, polyacrylate |
|
Solvent R-14 |
Epoxy enamels cured with isocenate hardeners |
|
Solvent R-24 |
Perchlorovinyl |
|
Solvent R-40 |
Epoxy |
|
Solvent R-60 |
Cresol-formaldehyde, polyvinylbutyral |
|
Solvent R-83 |
Epoxy ester |
|
Solvent R-189 |
Solvent for polyurethane varnish |
|
Solvent R-219 |
Polyester resin solvent |
|
Solvent R-1176 |
Solvent for polyurethane paints and enamels |
|
Solvent RL-176 |
Polyacrylate, polyurethane |
|
Solvent RL-277 |
Polyurethane |
Other beneficial features solvent data:
— cleaning and degreasing the surface;
— removal of paintwork materials from brushes, rollers, spatulas and other tools.
Video about what solvent to rinse the spray gun with
Solvents for removing paint: fresh and old
If, during the work, paint stains ended up in the wrong place (stained furniture, floor, glass), it can be removed with the solvents indicated in the table. True, for delicate surfaces (wood, laminate, plexiglass) you should not use combined compounds like R-646. It is better to use homogeneous ones and be sure to first test their effect on an inconspicuous area.
Special solvents are produced for removing old paints from large areas. They will help remove paint from walls, with metal products and so on.
Solvents for building materials
Removing frozen mortars often causes serious difficulties. Manufacturers have done everything to make them as resistant to chemical influences bitumen, concrete, polyurethane foam, etc. What solvents will help in this case.
Solvent for concrete, cement, grout- mixture concentrated acid, protective substances for metals and inhibitors.
Liquid glass solvent - Tools can be washed off with warm water immediately after application. Hardened material can be removed with organic solvents
Solvent for polyurethane foam - fresh foam is easily removed with ethyl acetate or solvents based on it (for example, P-645, 647). The solvent for hardened polyurethane foam can be considered folk remedy"Dimexide" (sold in pharmacies). Also "Dimexide" is excellent super glue remover.
Liquid nail solvent- uncured ones are removed with solvents mineral based or water. Hardened ones can be removed mechanically or by heating with a hairdryer to a temperature above 50°C
Rust solvent- special compositions based on phosphoric acid, tannin, hydroxycarboxylic polybasic acids.
Silicone solvent ( silicone sealant, glue)- along with special compounds from sealant and adhesive manufacturers you can use acetic acid or white spirit.
Polymer solvents:
— PVC- tetrahydrofuran, cyclohexanone for several days;
— polyethylene- xylene, benzene when heated;
— polyurethane foam- can only be removed with fresh special solvents from the manufacturers.
Solvent for rubber and caoutchouc - toluene and other organic solvents are suitable for removing the substance (rubber dissolves, rubber swells and breaks down)
Solvent bitumen mastic - toluene, solvent, gasoline, white spirit
Foam solvent - acetone, solvent R-650
Solvent for paraffin and wax- kerosene, white spirit, gasoline, acetone.
In the next article we will tell you about small household solvents and solvents that artists use.
Polyurethane paint (enamel
UR 1012)
Polyurethane paint UR 1012 is a two-component system consisting of semi-finished enamel and polyisocyanate hardener, mixed before use.
Semi-finished enamel is a suspension of pigments and fillers in a solution of polyester acrylate resin with the addition of solvents and targeted additives.
Polyurethane paint (enamel UR 1012 ) is intended for anti-corrosion protection internal surfaces tanks, tanks, storage facilities for light petroleum products, pumping and container equipment operated in an open industrial atmosphere of temperate, cold, marine and tropical climates, as well as in an atmosphere containing corrosive agents.
The coating system, consisting of polyurethane enamel applied to a primed surface, retains protective and decorative properties in an open industrial atmosphere in temperate and cold climates - 12 years, in an atmosphere of marine and tropical climates - 5 years, subject to installed technology application, storage and transportation rules.
Polyurethane paint (enamel UR 1012 ) is produced various colors in accordance with the RAL color chart.
Preparing the surface for painting
.
The surface to be painted must first be cleaned of mechanical impurities, water-soluble salts, fats, and oils. Degreasing is carried out with a rag moistened with solvent, xylene, acetone or other aromatic solvents.
The surface must be dry and clean before painting.
Cleaning from rust, scale, residues old paint done manually or mechanically up to St 2 or by shot blasting (sandblasting) to degree SA2 - SA2.5 according to the international standard ISO 8501-1:1988. This cleaning gives the required adhesion.
Preparation of polyurethane paint
to application.
Before use, semi-finished polyurethane paint (enamel UR 1012 ) mix thoroughly and add required amount hardener, mix, stand for 15-20 minutes. If necessary, polyurethane paints are diluted to working viscosity using a VZ-246 viscometer with a nozzle diameter of 4 mm at a temperature of (20.0 ± 0.5) 0C with solvent R-5A (according to GOST 7827-74) or a xylene mixture (according to GOST 9410-78 or GOST 9949-76) and butyl acetate (according to GOST 8981-78) in a ratio of 4:1. Recommended working viscosity when applied by brush or roller is 35 s, by pneumatic spraying – 8-22 s, by airless spraying – 45 s.
Polyurethane paints (enamels UR 1012 ) after dilution, mix thoroughly again and filter through a sieve with a 0.1H-0.2N mesh according to GOST 6613-86 or a similar imported sieve, or a synthetic fabric mesh (nylon, polyester or polyamide) with a nominal hole size of 100-200 microns according to GOST 4403-91.
Coloring
.
Polyurethane paints (enamels UR 1012 ) is applied to the surface using pneumatic and airless spray, brush or roller in 1-2 layers at ambient temperatures from 5 to 350C and relative air humidity not higher than 80%.
Polyurethane paintsapplied to a surface previously primed with FL and EP primers.
Theoretical consumption of polyurethane paint
(enamel UR 1012 ) for a single layer coating 80-110 g/m2.
Practical consumption depends on application method, degree of surface preparation and product configuration.
Guarantee period
storage of semi-finished products – 12 months from the date of manufacture.
The shelf life of polyurethane paint (a mixture of semi-finished product with a hardener) is at least 6 hours.
You can buy from us
polyurethane paints sUR 1012price:
The importance of solvents and their role in working not only on wood forces anyone home handyman It is better to know their types, types and properties, as well as what they are made of.
Although the terms "solvent" and "diluent" are often used interchangeably, these liquids have completely different properties. (However, for the sake of simplicity, we will primarily use the word “solvent.”) A solvent is a liquid that dissolves a solid, such as dried varnish. Thinner is a liquid that is used to dilute stain, paint or varnish to reduce viscosity.
Sometimes the liquid only dilutes the finishing composition; in other cases, it can not only dilute the varnish, but also dissolve the dried coating film. For example, thick alkyd-oil or polyurethane varnish can be diluted with white spirit, but after drying these varnishes no longer dissolve in it. On the contrary, denatured alcohol can both dissolve and dilute shellac (see table at the end of the article).
Learn to understand these substances, without which most finishing methods are impossible. First, let's combine all the liquids into main groups and find out how one group differs from another. Then we will look at the liquids included in each group and find out the differences between them. Having become familiar with the basic properties, you can understand how complex thinners consisting of different substances work.
Main groups of solvents
We will not now consider special solvents that are part of removers for varnishes and paints, as well as water, which is used to dilute water-based finishing agents and dissolves water-based dyes. In addition to them, there are five main groups of solvents used in finishing processes: petroleum distillates(petroleum distillation products), alcohols, ketones, ethers and glycol ethers.
Turpentine could be classified in the sixth group, but its working properties are very close to petroleum distillates, and it is better to include it in their group. Each of the five groups has its own characteristics. The most common are petroleum distillates, also called hydrocarbons, since the molecules of these substances consist of carbon and hydrogen atoms. The liquids included in this group are obtained by separating oil into fractions at different temperatures. Turpentine is also a distillation product, but instead of oil, the raw material for its production is resin coniferous trees.
Petroleum distillates are used to dissolve and dilute wax, oils and varnishes on oil based(including polyurethane). Many of them (such as mineral spirits, kerosene, petrolatum and paraffin) have properties that make them similar to wax or oil, and are often used as components of lubricants and furniture care compounds. Less oily distillates, such as toluene or xylene, easily remove oils and greases and are used for degreasing.
All petroleum distillates and turpentine can be mixed in any proportions. Compared to white spirit, turpentine is more oily and evaporates more slowly. Toluene and xylene are part of complex solvents and thinners for varnish, removers for acrylic paints and thinners for some two-component varnishes. With their help you can remove even dried IVA glue. Petroleum distillates are also used to dilute industrially produced oil-based stains.
Alcohols They are used as thinners and solvents for shellac and alcohol dyes, as well as components of varnish thinners. Ketones and ethers are used as solvents and thinners for nitrocellulose varnishes and paints.
Glycol ethers(for example, cellosolve - a trade name for ethylene glycol) also dilute and dissolve nitro varnish and are often used as a binding additive in water-based stains and finishing compounds. Thanks to these solvents, the latex particles of the composition combine and form a protective film on the surface of the wood after the water evaporates from the coating.
Differences within each group
The essence of the differences between liquids of each group is the same: the smaller the molecules of a substance, the faster they volatilize (evaporate), and vice versa, a liquid consisting of large molecules dries out slowly. In addition, large molecules often leave a greasy or waxy residue on the surface after drying, while smaller molecules evaporate, usually without a trace. The “Petroleum distillates” diagram will help you visualize the differences between substances of the same group that you most often deal with. The smallest molecules in this group are methane, which evaporates so quickly that at ordinary temperatures it is in a gaseous state.
Following methane in terms of the degree of increase in molecular size are ethane, propane, butane, etc., up to octane, a quickly evaporating liquid that serves as the main component of automobile fuel. Then come solvent and white spirit (petroleum solvent is less oily and evaporates faster than white spirit). Toluene and xylene are volatile liquids with pungent odor– obtained from solvent and white spirit. Manufacturers separate toluene and xylene, and the remainder is sold as odorless white spirit, which is weaker than ordinary white spirit, but wax dissolves in it and is suitable for diluting oils and oil-based varnishes. Toluene and xylene evaporate very quickly, leaving no traces. The next liquid with even larger molecules is kerosene. It is very oily and almost does not evaporate when room temperature. After kerosene comes mineral oil, which has all the properties of real oils, which practically do not evaporate. And finally, petroleum wax, or paraffin, is one of the main products of petroleum distillation. At room temperature it is not a liquid, but a solid that melts when heated.
So, we have listed almost all the main substances included in the group of petroleum distillates. Alcohols, ketones, ethers and glycol ethers differ from each other in the same way - the smaller the molecules, the faster they evaporate, and liquids consisting of large molecules evaporate slowly. Of these four groups, only alcohols and ketones are available and widely used in finishing. In the group of alcohols, methanol (wood alcohol) evaporates most quickly, much faster than ethanol, the alcohol contained in alcoholic drinks and also called spirit of wine. Ethanol, as a food grade alcohol, is subject to high excise duties, and to avoid taxation, toxic substances (usually methanol) are added to it, making it undrinkable. This mixture is called denatured alcohol or shellac solvent. Methanol itself is highly toxic, and you should only work with it outdoors or in a special spray booth with strong ventilation.
In the ketone group, acetone evaporates faster than methyl ethyl ketone (MEK). The remaining ketones evaporate slowly. You can recognize a solvent using the suffix in its name. Alcohols have the suffix “-ol” (methanol, ethanol), ketones have the suffix “-one” (acetone, methyl ethyl ketone), ethers have the suffix “-at” (methyl acetate, ethyl acetate, etc.). The names of liquids from the group of glycol ethers usually contain the word “ether”. But don't let all these names fool you or fool you. In most cases, you only need to remember the five main groups, each of which is used to dissolve or dilute certain substances. Within each group, the differences between the liquids included in it are not so significant and consist mainly only in the rate of their evaporation.
Solvent for nitro varnish
Having become familiar with the main properties of the various groups, you will be able to understand how the combined solvent for nitrocellulose varnishes works. Being a mixture of several substances, it can have different evaporation rates, and its properties depend on the composition and proportion of its components.
The main substance of the varnish is mine molecules of nitrocellulose, which under high magnification under a microscope look like spaghetti. To prevent them from sticking to each other and to make it more convenient to apply the varnish by spraying, a large amount of liquid is required. If the molecules collide when too close to each other, the varnish becomes viscous, and when applied by spraying, a so-called shagreen resembling the skin of an orange is formed on the surface of the film.
For spray application, the varnish should not be viscous; enough small quantity solvent to separate the nitrocellulose molecules from each other. The solvent for nitro varnishes usually contains about 40-50% of the active substance, which is a solvent for varnish molecules: acetone, ether or glycol ether. The rest can be any liquid that serves as a kind of “diluent for the solvent.” Typically, petroleum distillates are used, which do not dissolve the varnish, but only dilute it even more. These fluids are usually relatively cheap and reduce the price of the combined solvent for nitro varnishes. Approximately 50-60% of this combination solvent is diluent. Most often, toluene, xylene or a mixture of them are used, and sometimes the solvent contains a petroleum solvent. The cost of the combined solvent can be reduced even further by replacing part of the active solvent with alcohol, usually methyl alcohol. Although alcohols themselves do not dissolve nitro varnish, they dramatically reduce its viscosity when mixed with acetone or another active solvent. Therefore, in addition to the active solvent and diluent, combined solvents often contain a little alcohol, which serves as a so-called latent (hidden) diluent.
Knowing these properties, you can find out what is sold under the name of remover for nitro varnish and shellac, which is often used by amateurs to update finishing coatings furniture. As a rule, this is a common combined solvent. You can verify this by reading the names of the components on the label. To be used as a nitro varnish thinner, the combined solvent must have a carefully selected composition. Sufficient amounts of active solvent and latent diluent are required to completely dissolve the nitrocellulose molecules. Otherwise, the molecules stick together into tiny lumps, and a whitish coating often forms on the varnish film, well known to many carpenters who use nitro varnish for finishing. If you encounter this phenomenon and the applied varnish has turned white, lightly sanding the dried varnish film and spraying a solvent over it will help correct the situation, which will restore its shine and transparency. (Applicants to retail sales combination solvents usually contain an insufficient percentage of active solvent. To successfully correct a whitened nitro varnish film, we recommend adding a little pure acetone to the purchased solvent to completely dissolve the varnish particles.)
Manufacturers often claim that only the combined solvent they produce is suitable for working with their nitro varnish. However, if you do not have problems with the behavior of the varnish film, then there is no reason to switch to the solvent recommended by the manufacturer. If you apply nitro varnish using a sprayer, you probably already noticed it unique property holds well on vertical surfaces. It does not flow down like oil varnish, shellac or water-based compositions, and with careful work, drips do not form. The reason for this property lies in the long molecules of nitrocellulose and the rapid evaporation of the diluent. As soon as the stream of thinned varnish leaves the nozzle of the paint gun and turns into tiny droplets of mist, the thinner evaporates and the molecules begin to stick together again. Having reached the surface of the product, the varnish acquires high viscosity and does not flow down. The remaining solvent is only enough to level the varnish film, then these residues evaporate.
The percentage of active solvent in products from different manufacturers may vary; for this reason, the properties of combined solvents can vary greatly, as they are influenced mainly by the rate of evaporation of the active solvent. Combination solvents sold can be divided into three categories: standard solvents for nitro varnish and nitro enamel, evaporating at a “normal” rate; so-called leveling agents, which evaporate more slowly than standard ones; and fast ones (usually sold in auto cosmetics stores), which disappear faster than all others. Unfortunately, manufacturers do not have mandatory standards, so you have to experiment, selecting a combined solvent with optimal speed evaporation among all three categories. However, by mixing solvents from different categories, you can achieve the desired result. IN normal conditions(at a temperature of 24°C and an air humidity of 40%), the evaporation rate of the standard combined solvent is optimal, but in cold weather (5°-15°C) the nitro varnish diluted with this solvent dries very slowly. During prolonged drying, more dust particles have time to settle on the surface of the varnish film, and they are embedded in the varnish. The finishing process slows down significantly. Drying can be accelerated using a quick solvent or its partial addition to the standard one. In hot weather, droplets of nitro varnish simply do not have time to spread over the surface to form an even film. Sometimes they can even dry out in the air before they reach the surface.
The coating turns out rough and dull. If the surrounding air is not only hot, but also humid, the varnish droplets capture moisture and the coating film becomes whitish. You can get rid of three problems at once (poor atomization, premature drying and whitishness) by using a slow solvent or adding it to a standard one. If you live in a very humid climate and the slow-release solvent you are using does not remove the stain from your varnish, try other manufacturers' products to find a better one. Slow solvents can be used to combat shagreen, for applying varnish with a brush, and also for finishing complex products, such as chairs or the inside walls of cabinets and drawers, when some of the varnish settles on already dry surfaces. Achieve optimal result with combined solvents it is often possible only through experiments, since manufacturers do not inform about the evaporation rate of their solvents, and the drying time of the nitro varnish coating has to be determined by trial and error. But, with some experience and using the same brands of solvents, you will be able to completely control the finishing process.
Safety when working with chemical solvents and thinners
IN last years More and more water-based finishing compounds and safe removers are appearing, and this forces many to take a closer look at organic solvents and their effect on environment. There is no doubt that water-based compounds are the future of joinery, but the full transition will take time. Nevertheless correct use and solvent storage remains a critical problem for small workshops.
In fact, how many of us realize that solvent vapors are a greater threat than liquids? By learning some information, you will be more attentive to potentially dangerous substances and can reduce the risk to a minimum.
White Spirit– a liquid product of petroleum distillation, used as a thinner and a means for removing wax and oils, as well as washing brushes. It reduces viscosity, allowing deeper penetration into the wood and speeding up the drying of oil-based compounds. In terms of evaporation rate, it occupies an intermediate position between slowly evaporating turpentine and quickly evaporating solvent. It has almost no odor, which makes it difficult to determine the excess amount of its vapor in the air. Fortunately, white spirit is considered one of the safest solvents.
Turpentine- a liquid obtained by distilling the resin of coniferous trees. Used as a thinner and cleaning agent to remove oil stains. Due to its slow drying time, it may be preferable to mineral spirits in some cases. Has a strong unpleasant smell. In contact with skin, it is relatively safe, except for people with hypersensitivity. However, it is a fire hazard and can sometimes ignite spontaneously. Never store rags soaked in turpentine in the workshop, even if dampened with water.
Petroleum solvent– evaporates quickly, which can be useful in some cases, but it is also highly flammable. Remember the main rule: if the solvent evaporates quickly, it has low temperature flashes, therefore a fire hazard. Do not use flammable liquids indoors, such as solvent or combined solvent, the vapors of which can ignite from the slightest spark in the room. electrical outlet or switch. Solvent is commonly used to remove traces of wax and oil, as well as to soften and polish shellac-based mastic.
Solvents for nitro varnish- a mixture of several liquids, the properties of which vary depending on the brand. For better compatibility It is usually recommended to use solvent and varnish from the same manufacturer together. Solvents have Strong smell, and this makes working with them unpleasant. When added to nitro varnish, they improve the spread and leveling of the coating film, making the gloss more uniform. They also provide better adhesion due to more deep penetration into the wood and speed up drying. Like solvent, they are not recommended for use indoors due to their high fire hazard.
Methanol– a very effective solvent and thinner for shellac and other alcohol-based compounds, but it causes corrosion of many metals and damage to finished coatings. Despite its excellent working properties, it is one of the most dangerous solvents. For safety, it is better to replace it with ethyl or isopropyl alcohol. Methanol, like methylene chloride, requires very careful handling. Regular carbon filters respirators do not retain the vapors of these solvents. When purchasing a respirator, find out whether it is designed to handle these substances. Remember, not all respirators are created equal.
When working with any organic solvents and thinners, follow the rules fire safety and personal hygiene, so as not to put your health and life at risk. Make your workshop a place where you can work without fear of trouble.
What solvent to dilute, what to dilute - table
SUBSTANCE | DISSOLVES | DILUTE |
White Spirit Solvent Turpentine | Wax | Wax Oil Oil varnish Polyurethane |
Toluene Xylene | Wax Water based coatings | Wax Oil Oil varnish Polyurethane Modified varnish |
Alcohol | Shellac | Shellac |
