Errors and defects in varnishing. White spots on furniture. How to get rid of Why matte polymer varnish has turned white

car paintingit's complex technological process where the chance of defects is very high. Especially if the painting is not done by a professional painter and without for car painting. In this article, we will look at the most basic and commoncar paint defects.

If you are a beginner, do not have enough experience and practice, then the occurrence of defects during painting increases significantly.
Defects appear from various factors, such as: inexperience of the master, unsuitable conditions, correct use material, etc. Below is a list of the main paint defects, their possible causes and recommendations for their elimination.

In the most severe cases, with loss of adhesion, the top layer of paint easily separates from the primer or old paint, or all layers are separated from the metal together.

Basically, weak grip is limited to areas that are sensitive to impact or shock. This defect is usually detected immediately after painting when removing the masking tape.

Poor adhesion is the result of insufficient bonds between the paint film and the surface to which it is applied. This is usually due to insufficient cleaning of the surface and poor preparation for painting, or adhesion can be broken later by exposure to moisture or other damage to the film.

The main causes of poor adhesion are:

Poor quality, because of which pollution remains on it (wax, oil, water, rust, dust, etc.). These contaminants prevent the strong adhesion of the paint layer to the surface.
Insufficient smoothing of the primer layer with filler before painting.
Insufficient mixing of materials
Use of primers not suitable for either metal or paint.
Incorrect application of paint ("dry" spray).
Using an unsuitable surface for painting.
Using the wrong solvent
Too fast masking of a freshly painted surface in two-tone coatings.
Improper masking can damage the paint layer when removing the masking tape from the surface.
Exposure to high temperature for too long during heat drying of the vehicle or excessively high drying temperature.

Remove the paint layer on the area, much larger area damaged area, with grinder or sandblasting machine (if necessary to metal).

If the loss of adhesion is due to lack of masking, treat the damaged surface and then paint it again.

Bubbling consists in the formation of bubbles of various sizes and densities on the surface of the paint layer. Bubbling appears on both new and old layers, and mainly appears at a time when high humidity is replaced by severe frosts.

Bubbles are caused by moisture or air trapped under the paint layer. Water penetrates even through the most the best coatings at a time when the body is exposed to sudden changes in temperature. Moisture that has entered the paint layer expands, and thus pressure is formed. This weakens the adhesion between the layers and thus leads to the formation of bubbles.

The most common cause of blistering is improper surface cleaning and preparation for painting, leaving dirt between filler and metal or between primer and paint. Typical contaminants are oil from air ducts, grease from fingers, dust, dirt and salt. Therefore, make sure the surface is clean and clean before painting.
Using the wrong solvent.
Excessive thickness of the paint layer and insufficient waiting time between coats. This can lead to buildup of solvent in the paint. Later, as the solvent evaporates, bubbles form. Therefore, do not accelerate the drying of each layer of paint in an unnatural way.
Inadequate thickness of the primer coating to the paintwork.
Exposure to dampness or moisture prior to painting, as well as continuous further exposure to these factors.

In case of severe bubbling, remove the paint to the metal, then completely repaint the surface.

If there is less bubbling, clean up the bubbling area and either apply only a thin coat of paint or refinish the surface.

The paint film does not shine well, does not cover the primer and metal well. Usually this film has flat surface, does not lag behind and does not bubble.

Too thin paint layer.
Poor preparation of the work surface or use when smoothing too coarse sandpaper.
Defect during priming.
Poor fixing of the primer on the surface.

If the paint layer is too thin, reduce the solvent content of the paint.

In most other cases, it is necessary to re-smooth, then carefully prepare the surface (using appropriate preparations where necessary) and apply a coat of paint of the appropriate viscosity.

Small bubbles in the paint layer, on closer inspection having tiny holes at the tops. This phenomenon is mainly observed at the boundaries of regions with a thick coating.

Solvent bubbles form in a thick layer of paint, which in turn forms for the following reasons:

Too much ink supply ().
The viscosity of the paint is too high.
Too slow movement of the spray gun (more than necessary amount of paint is applied to a small surface).
Too much large overlap spray paint layers.

Leave the painted surface to dry completely before smoothing and applying the final coat of paint (the drying time of oil paint is highly dependent on the thickness of its layer).

Haze appears as a milky white "fog" on the painted surface. If haze is present on the paintwork, then it may also be present on the primer. Note that the haze on the primer may not be noticeable (as it is usually matte), but it may later develop into blistering or loss of adhesion.

Haze can occur if painting is done at low temperature and high humidity, and is caused by moisture trapped in the paint layer. During the spray painting process, the solvent evaporates rapidly, resulting in a cooling of the area to be painted. Moisture from the surrounding air condenses on the fresh paint coat, resulting in a milky white "fog". Possible reasons this:

Use of low-quality (cheap) solvent.
The use of a fast evaporating solvent at low temperatures and high humidity. Under these conditions, a special type of solvent must be used. In addition, use the minimum amount of thinner, otherwise the drying process of the applied coating will be significantly slowed down.
Spray gun operating parameters set incorrectly, painting technique incorrect or overpressure air.
Incorrect air circulation or insufficient temperature in the workshop.
The solvent evaporates too quickly when directing a jet of air onto the paint layer.
Draft in the workshop.

In case of slight haze, wait for the paint to dry completely and eliminate the defect by polishing.

Repaint defective areas using a special solvent.

Spray the defective areas with the above special solvent. Under the right conditions, this will eliminate haze.

If none of the above methods work, increase the temperature in the workshop by at least 5° and ensure that there are no drafts.

The microcrack defect is a large number of very small, unrelated cracks that require a magnifying glass to view. On the paintwork, microcracks appear as dull spots and lack of gloss. Cracking is a set of random cracks, often in the form of three-pointed stars. It resembles cracked mud in dried-up ponds or on the banks of rivers. These cracks are usually quite deep and penetrate the top coat of the paintwork and sometimes even the primer/filler. Cracking is usually the result of weakening of the paint film, such as microcracks or blistering.

Cracking occurs as a result of the weakening of the paint layer, which occurs under the influence of conditions environment. Modern quality paints, when properly applied, rarely crack. The latter appears for the following reasons:

Too thick paint layer. Applying too thick coats of paint or primer increases the stresses and strains normally present in any paintwork, and this leads to cracking even under normal conditions.
Insufficient drying time. The risk of cracking is increased when thick layers of paint are applied on top of each other without proper drying time.
Insufficient mixing of paint before use. Poorly mixed paint affects the strength of the paint layer, its flexibility and adhesion, which in turn leads to cracking.
Insufficient cleaning and surface preparation for painting.

Sand the defective areas to a smooth surface, although in most cases it is necessary to completely remove the paint to the metal and repaint the surface.

Paint craters are small, funnel-shaped holes in the paintwork that form during or immediately after spray painting a vehicle. The reasons

The appearance of craters is caused by silicone particles. Silicone contains many modern waxes, paraffins and polishes. It adheres strongly to the surface of the paintwork and requires additional measures using alcohol mixtures to remove. Craters appear for the following reasons:

Insufficient cleaning of the surface and poor preparation for painting. Contaminated surfaces are washed with soap and detergents. It is necessary to take measures to remove traces of silicone from the surface with the help of grease and wax removers.
Pollution can also occur during surface preparation for painting: from sand dust, lint from used rags, automotive polishing paste. Even applied for a short time, these substances can cause surface contamination, which in turn will lead to the appearance of craters.
Oil in the air duct of the spray gun. The use of silicone containing anti-crater additives is not recommended. These additives can contaminate the workshop, which can lead to loss of traction when doing other jobs.

Smooth out defective surfaces and apply a new coat of paint.

Rough, unevenly painted surface.

Too fast evaporating or inappropriate solvent, low
humidity and high ambient temperature
air.
Too high fluidity of the paint.
Air pressure too high.
Too thin paint film.
Spray distance too long.
Poorly prepared primer.

If possible, polish the surface of the part. If the defect is too strong, repaint the part with paint or varnish.

This defect is small cracks or gaps on the sharp bends of the panels in the areas of touch-up. They appear during or immediately after applying the paint layer to the primer.

Paint film too thick without proper drying. This leads to the accumulation of solvent in the layer, which in turn causes cracking.
Poor mixing and use of poorly mixed paints with solvent primers. This leads to a reduced pigment content in the paint, which causes the creation of a spongy surface structure. When the top coat of paint is applied, this structure can collapse, causing shrinkage and gaps that lead to sagging.
Too fast-acting primer thinner preventing uniform application of the paint coat.
Insufficiently cleaned surface and inadequate preparation for painting. If the protrusions (sags) in places of minor surface repair are not sufficiently cleaned, then the applied primer layers can “slide” down from these protrusions due to poor adhesion.
Blowing through the primer layer with a spray gun immediately after its application. This dries the surface of the coating before the air has escaped and the solvent has evaporated, causing shrinkage and cracking of the dried layer.

Remove the top layer of paint from the surface and repaint it.

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More matte surface than normal glossy. Note that two-component paints and paints applied with , give a higher gloss.

Too thin paintwork.
Smoothing scratches.
Uneven coloration (spotting) (see relevant chapter above).
Not enough paint.

Re-smooth the surface and apply the next coat of paint.

The uneven surface of the paint layer, similar to orange peel called shagreen. The reasons for the appearance of large shagreen are caused by a lack of spraying of paint, which manifests itself in poor merging of drops on the surface, i.e. drops stay in place (in the order in which they flew out of the spray gun) and do not spread over the surface. Ideally, the drops should spread and mix with each other, thus forming smooth surface. The reasons for the formation of shagreen are as follows:

Incorrect or incorrect spray gun adjustment, air pressure too high or too low, distance between gun and surface to be painted too large, paint flow too low or air jet too wide.
The air temperature in the workshop is too high (use slow evaporating solvents).
Materials not mixed enough. Many topcoats contain droplet agglomerating agents, so if the paint is not agitated, an "orange peel" defect may occur.
Too thin paintwork.
Incorrect ink viscosity.
The drying time between the application of individual layers was not maintained; air flow from the spray gun was used to reduce the drying time.

So how to remove shagreen leather after painting a car. After the paint has completely dried, clean the defective area with an abrasive compound or sandpaper (choose grit depending on the condition of the surface). Restore gloss with polish.

In severe cases, smooth out defective areas with fine-grained sandpaper and repaint the surface.

One of the layers of paint peels off or easily separates when removing the adhesive tape after masking is completed from the other, previous layer. This can happen both during the initial painting and when repainting.

Contamination between layers: oil, dust, water, etc.
Excessive exposure to high temperatures or excessively high temperatures when applying a primer or top coat of paint.
Too thin primer or top coat.
Poorly carried out interlayer smoothing, resulting in poor adhesion of paint layers.
Incompatibility of primer, paint and finish coats

Smooth the surface down to the base layer and thoroughly clean the surface. In rare cases where an earlier repaint has taken place, it may be necessary to start from bare metal.

One of the most common defects is probably a smudge. Drops, smudges and flows of paint on vertical or inclined surfaces of the body.

The solvent in the paint evaporates too slowly.
Too thick layer of paint.
Subsequent layers were applied without sufficient exposure of the previous ones.
Too small distance between a paint gun and the processed surface -.
High pressure air.
Spray intensity too high.

How to remove smudges and influxes of paint and varnish on the details? If the smudge is not large, then it can be removed with fine sandpaper and a bar, and then the surface is polished. If the influxes and smudges are significant, then the part will have to be repainted. remember, that oil paints dry rather slowly, and the depth of the influx of such paint can be significant; in many cases an additional coat of paint is not required.

"Dry" or "semi-dry" drops of paint from the spray gun form a coating of particles that do not adhere to the surface.

Fast drying paint used.
Incorrect solvent used (too volatile) in warm, dry conditions.
Wrong spray technique applied, i.e. overspraying on neighboring (painted or unpainted areas).
Excessive kickback caused by incorrect air pressure, viscosity or spray gun settings.

Lacquer overspray is usually dry and does not adhere strongly to the surface, so it can be eliminated by sanding the partially dry film.

Overspray of synthetic enamel is usually wet and adheres strongly to the painted surface. Many of these materials are difficult to polish, so overspray must be removed with a wet smooth and a new coat applied.

The fine pores on the surface of the finish coat are tiny holes (often clustered) in the painted surface.

Micro-holes can occur different reasons and are caused by the ingress of solvent, moisture or air into the paint layer and their subsequent release (drying). This is often due to poor paint preparation or the use of incorrect painting techniques, and can occur in primers, and paint coatings. Pinholes can be caused by the following reasons:

Spray gun settings incorrect or incorrect operation. The gun was too close to the work surface. Insufficient spraying of the primer or paint coat. Pinholes form when air or excess solvent escapes from a painted surface as it dries.
The impact of a jet of air on a freshly painted surface. It leads to air getting inside the paint layer and drying it too quickly.
Applying a paint coat on top of a primer or paint coat, made by "dry" spraying.
Jet contamination with oil from the compressor or moisture.
Application of heavy coatings with insufficient drying time for each coat.
Incorrectly used putty knife when applying putty or filler. Using the knife at a sharp angle causes the material to roll under the blade and air bubbles inside the material.
An error in determining the area for the application of filler or putty.

Where pinholes are minor imperfections, they are removed with filler or smoothed out with fine sandpaper and then reapplied with filler.

In other cases, wet smooth the defective areas of the coating to a depth that guarantees complete elimination of pinholes, then repaint the defective surface. You can also remove defective paint to bare metal and repaint.

Micro-holes which, after smoothing, have been exposed to filler or putty, must subsequently be filled with a thick layer of putty using a putty knife, which should be held at an angle of 90° to the surface. In this case, the putty is well pushed into the micro-holes.

Note: If you are concerned about pinholes, check all the factors that cause the paint to dry quickly: paint viscosity, solvent type, ambient temperature, etc.

Almost always paint dust and debris manifests itself in the form of an uneven accumulation of particles different sizes on the paint layer.

Debris and dust particles can get on the painted surface during or after painting. In any case, the cause lies either in non-observance of cleanliness, or in the use of paint that does not correspond to the working conditions of painting. Contamination of the painted surface is facilitated by:

Paint or solvent contamination. Garbage, of course, could not be in hermetically sealed cans of paint and thinner before they were opened, but could enter when a dusty can was opened or if incompletely used materials were not properly stored.
Dust not removed after primer treatment.
Air pollution. It can come either from the immediate environment or from more distant sources. Slow-drying paints (e.g. enamels) require a clean indoor environment for use for two reasons: the increased drying time results in high probability dust settling on a freshly painted surface; unlike cellulose paints, gloss on enamel coatings not restored even with polishing.
Poorly cleaned instruments and filters. It happens that when changing paint, a more active solvent is used, which softens and takes away with it the dried dirt accumulated in the paint gun.

→ White spots

You can remove white spots on furniture from alcohol, acetone, iron, water in various ways. Polishing, varnish regeneration, complete replacement varnish coating. Our workshop removes white spots in both full and partial restorations.

White spots are destroyed varnish. Removed by removing damage followed by polishing. They arise for various reasons, the result of which is the destruction of the film or its delamination from the surface of the tree. Removing white spots is much more difficult than preventing their appearance.

White stains from alcohol

Alcohol-containing liquids leave white spots due to the chemical activity of the solution. Alcohol molecules react with the molecules of the lacquer finish, destroy it, and the transparency of the lacquer is disturbed. Not deep destruction of modern varnish can be tried to be eliminated by polishing. To do this, we remove the damage with a thin abrasive paste until the polishing remains intact. The varnish will become thinner, but there will be no stain.

Prevention measures: cover the countertop of expensive furniture with cut-to-shape organic glass.

Acetone stains

The mechanism for the appearance of stains from acetone is the same as in the previous case, but acetone is more active, the destruction occurs deeper, faster. Correction of the defect by complete replacement of the finish with varnish.

Spots from iron, hot, direct sunlight

White spots are left by cups of hot drinks. Very ugly marks in the form of crescent circles are the result of exposure to hot cans, glasses, bottles.

When heated, the polymer, which is any modern varnish, changes its density, therefore, the physical properties change, namely, transparency. This happens throughout the depth of the finish. Elimination - complete replacement in a restoration workshop by a professional restorer, using special equipment.

White spots from water

Appear on antique furniture finished with shellac. Or modern furniture after using expensive care products containing wax, dyes, natural resins (rosin, shellac). When interacting with moisture, the resin turns white, the dye discolors. If the agent turns white, it is removed with a dry cloth. If the shellac finish has fallen into disrepair, restoration cannot be avoided.

Shapeless light spots appear on the modern wooden furniture due to moisture ingress under a layer of durable moisture-resistant varnish. Water through cracks and scratches that has fallen under it does not evaporate for a long time, it impregnates the wood, provoking delamination. In places of damage, color distortion is observed.

Currently, there are a large number of modern durable products for coating wooden surfaces. Special varnishes for wood coating in conditions of high humidity, temperature changes. Everything about these varnishes is wonderful, one thing is bad - they are not suitable for antique furniture. Modern varnishes give wood the appearance of plastic. Only oil-based polishes and varnishes are suitable for finishing antique furniture.

All alcohol polishes for wood, which covered furniture from the 18th century until the 60s of the 20th century, are destroyed by moisture and high temperatures. Even wet air, penetrating into cracks, provokes damage in the form of white spots.

Polishing furniture with polish is a long and laborious process that requires patience and skill. There was a separate profession - polisher. Since shellac polishing is gentle, every six months, a polisher was invited to rich houses with expensive furnishings who polished all the furniture, cleaning and cleaning along the way. white coating. Over time, the layer of shellac increased. Shellac varnish has a golden Brown color, with increasing thickness, the intensity of color also increases. So vintage furniture becomes more beautiful over time.

The diagnosis is as follows: the varnish has turned white. Lost transparency. Like org. glass after exposure to a chemical or abrasive. This could happen for several reasons.

1. Lacquer does not dry

· Substances (natural oils, resins, etc.) contained in the thickness of the wood make it difficult to dry. For example, in some cases, when working with varnishes based on artificial resins, exotic breeds wood;

· Old, waxed floors - wax residues delay the drying of PU-, acid-cured and artificial resin-based varnishes;

Too little or completely missing hardener (for two-component varnishes);

· Too much low temperature indoor air (below +10°);

High air temperature in the room, but low temperature of the parquet, respectively, insufficient supply of oxygen (difficult to access fresh air);

· Wrong hardener used, eg hardener for PU varnish added to acid curing varnish.

If the delay in the drying of the varnish is due to substances contained in the wood or too low a temperature, then to eliminate this problem, it is usually sufficient to raise the temperature to + 20 ° C and provide good air access ( not a draft!!!). After some time, the drying process is activated again and the varnish dries normally. If you use the wrong hardener, the varnish will most likely have to be washed off. In some cases, for acid-curing varnishes, it is sufficient to apply a thin layer of pure hardener to the adhesive surface. However, after the varnish has hardened, the entire surface will need to be completely re-sanded.

2. The appearance of cloudy, white spots and tracks

· The temperature of the varnish used was too low;

· The floor temperature was low. Humidity is very high;

· The general humidity in the room (especially in new buildings) is too high.

White spots always indicate that condensed excess moisture has fallen on a fresh varnish film. It is usually sufficient to treat the whitened areas with a solvent, pay attention to the content of dangerous substances in it! In any case, after this operation, it is necessary to apply another layer of varnish, having previously raised the temperature in the room to the required value.

3. "Bloating" (swelling) varnish

· Wrongly selected scheme for constructing a varnish layer - for example, solvent-based PU varnish is used with a nitrocellulose primer;

The “wrong” solvent;

· The working tool is still impregnated with a cleaner, which is mixed with the used varnish.

“Bloating” in a limited area can be eliminated by grinding and then applying another layer of varnish, but if the entire surface has “raised”, it is necessary to completely grind off the entire varnish and apply it again.

4. Bubble formation

· Cold varnish;

· Too thick layer of varnish;

Direct hit sun rays;

· Unsuitable rollers or brushes.

Bubbles in varnish occur when a film has already formed on the surface of the varnish layer, and its lower part remains liquid. Evaporating, rising solvent vapors tend to “break through” the film, thus “blowing out” bubbles. The only way out is complete sanding and re-lacquering.

5. "Scaling", layering varnish

Too high temperature in the room or on the surface of the floor;

· Too thick layer of varnish;

· Slow pace of work;

· An unscrupulous approach to the mode of work or the “wrong” working tool.

By adding a solvent, you can change the viscosity of almost any varnish, thus increasing its fluidity. But usually it is enough to change the rhythm of the work, minimizing the time of "docking" the previously treated area with the new one. During the heating period, the temperature of the batteries should be significantly reduced. Avoid drafts!!!

6. The formation of "craters"

the working tool is out of order (especially the rollers);

wrongly chosen solvent;

draft;

the varnish is too cold;

The surface is contaminated with silicone.

Craters can be eliminated by careful (matt) intermediate grinding and no less thorough surface treatment with a metal spatula, the so-called "ZERO-PUTTY". The varnish applied with a spatula should dry well, it should not be sanded. After that, another layer of varnish is applied. Very many parquet lacquers are prone to this “disease” in places of drafts, as well as if the lacquer has been stored for a long time at a very low temperature and spreads poorly (“thick”).

7. "Roughness"

Evenly distributed bubbles;

· Small particles of a varnish film from a working capacity;

· Wrong grinding.

"Roughness" often causes the greatest difficulties, since incomplete data are often given about the causes of its occurrence. In fact, the basis of most complaints is dirt, although often the cause of roughness can only be determined with a magnifying glass. Lumps of varnish from the working container are the second most common cause. Therefore, it is especially important that before starting work, all tools, containers and work clothes were perfectly clean. Varnish containing solid particles must be passed through a sieve.

8. "Wrinkles"

Too early application of the subsequent layer of varnish;

Too thick application of the subsequent layer of varnish;

The “wrong” solvent.

This phenomenon is observed in particular with varnishes based on artificial resins - with too thick or fast application of each subsequent layer of varnish. In the event that the entire surface is covered with “wrinkles”, a complete regrinding is indispensable.

9. Matte-glossy areas, the formation of "clouds"

Many matte varnishes are designed to be applied with a layer of max. up to 150 g/m. square. When applying a thicker layer, the matting substances “spread out” unevenly, settling in each fresh layer. As a result of this, matte-glossy areas appear, especially in the “joining” areas. You can correct the situation with the help of intermediate grinding and subsequent application of a matte varnish in a thin layer.