What are the solutions to clearcoat defects and “orange peel”?

In the many painting professions, such as industry, bottling, lacquering, or bodywork, the final step is generally the covering and varnishing of a paint with a clearcoat.
The clearcoat is a shiny and transparent coat that protects and improves the appearance of the paint by creating a smooth and shiny appearance. This is where various annoying defects can appear, the best known of which is "orange peel skin". Under this expression of orange peel in paint, hides a defect of appearance which is due to a bad technique of application, a bad drying, or even to bad conditions of application.

In this article we give:
► tips to avoid the orange peel phenomenon
► a tutorial to correct the orange peel defect
► a tutorial to avoid and correct the 5 other common clearcoat defects

Orange peel on nail polish appears as a wrinkled, rough, imperfect surface. To show a perfect shine, the surface of this varnish should be perfectly smooth. And if one has a dark color underneath, one could see its image reflected like on a mirror. On the contrary, when there are surface defects, the shine decreases and the reliefs of the surface are seen both near and far, greatly reducing the shine.

In car body painting, the final stage of varnishing is clearly one of the most important because it crowns all the previous stages, with a perfectly sanded primer, a very fine and very smooth matt base paint. It is also the varnish that will make all the mother-of-pearl and metal particles present underneath in the paint shine.

It is always tricky to apply clearcoat, unlike the painting and priming steps, which are considered much easier by all painters. The secret of a successful clearcoat is a sum of parameters and rules to be respected, without which all sorts of defects can appear and spoil all the good work done upstream.

We invite you to read our tutorial on « how to correctly apply bodywork clearcoat ».

Advice to avoid orange peel and clearcoat defects?

1 ► Correctly adjust your paint gun:
To shine, a polish must be applied with a thick layer applied in one go.
Use a nozzle of sufficient size (1.3-15 mm)
Open the Maximum “flat” jet
Set the air flow to 3 bars
The trigger must be able to be fully depressed without limitation in its amplitude

2 ► Mixing the clearcoat
a varnish that is not sufficiently diluted will not be able to stretch and level itself well. On the contrary, a varnish that is too diluted can run and suffer a drop in the level of shine.
Use a hardener that matches the ambient temperature of application
Add the minimum and necessary dose of diluent
Use the varnish 5 minutes after mixing, and before 20-30 minutes

3 ► Ambient temperature
It is important to monitor and control application conditions. One of the common causes of orange peel is too high an ambient temperature.
Painting in a dry and non-humid environment
Painting at a temperature between 15 and 25 degrees Celsius
it is possible to paint in cold or very hot temperatures, with a hardener and a suitable thinner, that is to say slow or fast.

4 ► Application
Here is the last parameter to control to avoid orange peel skin. This is the gesture made with the gun. Very often, the orange peel phenomenon is a lack of shine, and forms a grainy surface, caused by the application of too thin a layer of varnish.
Adjust the movement speed from left to right: if it is too fast, the quantity of varnish deposited will be too low.
Adjust the distance of the gun from the support: if the gun is too far away (+15cm), then the varnish may partially evaporate before touching the support, and there may be a lack of thickness deposited. Fully depress the paint gun trigger. You should not apply a thin layer when varnishing.

The correct and optimal application of the clearcoat begins with a good adjustment of the gun. This requires sufficient air flow and maximum spray jet opening, when painting a large area such as a car or motorcycle.

Second is the mix. Like everything in the bodywork business, just doing things carefully and meticulously can avoid all sorts of problems whose causes can be difficult to disentangle. The mixture must be done with precision and it must be left to stand for 5 minutes in order to allow the start of polymerization. On the contrary, this mixture should not be used beyond the “Pot life” period.
Dilution is an important issue. First of all, you should never abuse the amount of thinner in the varnish. Not only can too much thinner cause the varnish to smudge, but it will also reduce gloss, as too many solvents will have to evaporate through the varnish layer during drying.

Here is the 3rd point and probably the most important, to avoid orange peel problems in the clearcoat. It is important to take into account the speed of the thinner and the hardener, but also to take into account the ambient temperature. Often, orange peel forms during the drying of the varnish, when the hardener or thinner is too fast and/or the ambient temperature is too high. In such a case, the surface of the varnish dries too quickly and wrinkles. You can paint perfectly with a summer temperature of 30° and obtain a varnish without orange peel, using a slow hardener and a slow thinner.

Finally, here is our 4th tip, which is also one of the essential points for the success of nail polish. Very often, orange peel skin is simply an application problem. When not enough clearcoat is applied to the surface in a single coat, often for fear of running, then the varnish is not loaded enough to be able to smooth out. To obtain a taut, smooth and shiny surface, a sufficiently thick layer must be applied.

Correct the “orange peel” phenomenon on bodywork clearcoat

There are mainly 2 solutions:
1 ► Sand then apply a new coat of varnish or
2 ► Carry out polishing (possible in the case of a moderate defect)

It is extremely easy to correct the appearance of clearcoat by restarting the application. This can be done after a few hours for a quick polish or the next day for a classic polish.
The procedure is as follows : first, surface sanding is carried out with a P500 grit abrasive sheet and a little water.
The sanding will smooth the edges of the uneven surface of the clearcoat and smooth the surface. Sanding with water allows for a smoother action and less clogging of the sandpaper.
No, finer sandpapers should not be used, as many professional painters or hobby applicators do . If you want to guarantee a perfect grip of the clearcoat on the clearcoat, you simply have to follow the recommendations of the technical sheet of the manufacturer of this clearcoat : beyond P500, we are normally outside the recommendations, even if in practice, a varnish hangs in appearance correctly on a surface sanded with P800 or P1000.

Correction of orange peel skin by polishing

This is often the technique preferred by applicators, even if it often represents as much work, if not more than the application of a new coat of varnish.
Polishing will be more or less easy depending on the importance of orange peel skin.
It will be necessary to start by reducing the relief defects with a P1500 sanding disc, then P2000 and P3000. The shine is then restored "artificially" by polishing with sheepskin, then a very fine black foam.

Polishing is a good option when you don't want to run the vehicle through the paint booth again and the defect area is of a reasonably small size.

How to avoid the different defects of bodywork clearcoats?

>We present below the 5 most common bodywork clearcoat defects, with advice on how to avoid them, and the corrective technique for each case.
1 ► Loss of shine
2 ► Micro bubbling
3 ► Openings or silicones
4 ► Detachments
5 ► Drops and runs

The varnishing is the most difficult exercise, it is the most delicate final touch which crowns all the efforts and the painting work carried out previously. How to obtain maximum shine, and especially how to maintain the shine of a bodywork varnish, which can often see defects appear just after application or during the drying period.
Above all, there are classic type automotive varnishes, with long drying times, and for which baking is recommended, and bodywork varnishes called “air drying” which dry quickly and which are used for small surfaces.
During periods of desolvation (evaporation of solvents), then drying “to the touch” (surface hardening), then drying thoroughly, it is possible to see the perfect shine appearance of the shiny and transparent layer deteriorate. finish, with the appearance for example, to name only the most common defects, of runs, micro bubbling, mattification (burial of shine).

1 - Loss of shine, or “burial” of the clearcoat
Symptom: upon application, the clearcoat is perfectly shiny, and as it dries, the shine disappears and gives way to a satiny and not smooth surface.

Common causes
♦ The hardener is damaged because it is too old, has been ventilated too much, or has been stored in a place that is too hot for too long a period of time.
♦ The application and drying temperature is too hot. It is important to let the clearcoat dry at room temperature (20-25°C). When the surface film of the wet clearcoat dries too quickly, it traps the solvents in the core of the clearcoat. Likewise, when cooking without having waited around ten minutes for the solvents to evaporate, this type of defect can occur.
♦ Excess thinner: it is important to add the minimum quantity of thinner to the clearcoat mixture. Certainly the thinner provides a perfectly smooth and shiny surface during application, but an excess of thinner will affect the shine of the clearcoat resin when drying.
♣ Corrective measures: This simply involves doing a light sanding and then reapplying the clearcoat properly.

2 – Micro bubbling
Symptom: micro bubbling appears a few minutes after clearcoating, in the form of numerous and microscopic dots, appearing in the thickness of the clearcoat. These are micro bubbles of solvents.

How to avoid orange peel and clearcoat defects? Apply a flawless body clearcoat
Micro bubbling is due to the trapping of solvents in the paint or clearcoat layers, due to too rapid a succession of layers and/or too high an ambient temperature. Anyone who has experienced this defect once, generally takes care never to take the instructions in the technical data sheet lightly again... Because the result of saving a few minutes is having to sand everything again and start all over again. work.

The causes :

♦ Too many coats of primer or paint have been applied. It is recommended to apply the necessary amount and it is not recommended to apply too thickly.
♦ The timeout between layers was not respected. The layers were stacked on top of each other too quickly.
♦ Paints and other primers were applied in too hot an environment: the surface layer closed without allowing the solvent to escape.
♣ Corrective measures: to correct this type of defect in a clearcoat, simply sand with P500 abrasive paper, at least to the depth of the bubbles. New coats of clearcoat must then be applied. In general, this is enough to completely eliminate this micro-bubble defect.

3 - Openings or silicones
Symptom: this is a common fault that can occur when applying a bodywork clearcoat. This defect is manifested by the appearance of holes measuring up to 3 mm, which leaves the paint underneath exposed. These are openings of the clearcoat on the paint: the clearcoat cannot properly moisten the surface and spread. This shows a lack of surface tension, or incompatibility, most often due to invisible contamination, and in particular the presence of silicone particles.
Meticulous degreasing prior to clearcoating generally guarantees the avoidance of these types of defects.

♣ Corrective measures: to correct this type of defect, you must first carry out surface sanding with P500 abrasive paper. Before reapplying the clearcoat, check that the gun or clearcoat used is not contaminated.
It is not necessary to completely sand the clearcoat. It is perfectly possible to leave the openings, and sand the clearcoat to half or ¾ of its thickness.
We then proceed to apply 2 new coats of clearcoat. It is important to start with one or 2 coats of very thin and/or further diluted primer, to ensure that the clearcoat will not open again. Only after 10 minutes can a new thick and shiny coat of clearcoat be applied.

4 – Detachments
Symptom: this defect mainly occurs with perfectly dry and hardened clearcoates. We can see this defect occurring frequently on older vehicles, with a whole portion of the clearcoat dissociating from the base paint, and peeling off in patches.

The cause of this defect is clearly identified, because it is an adhesion defect, due to incorrect application, and which can occur in the following two cases:
♦ The clearcoat was applied to dry paint, not sanded, or sanded too fine: it is imperative to sand the paint, with the grain recommended by the clearcoat technical sheet. In general, sanding finer than P500 cannot guarantee good adhesion.
♦ The clearcoat was applied "wet on wet", but the deadline was not respected, or too hot a temperature caused the base paint to dry faster than expected: the surface of the paint closed and the clearcoat could not adhere correctly.
♣ Corrective measures: this consists of blowing with a blow gun and compressed air all the areas of clearcoat which are not adhering correctly. Then sand the clearcoat with P500 paper or a gray abrasive sponge, then apply 2 coats of clearcoat.

5 – Drops and runs
This is a common defect which can occur after application of a clearcoat, both by an amateur painter and by an experienced painter.

Here are the different causes of clearcoat drips:
♦ Application and drying temperature too low: the hardening of the clearcoat is slowed down and gravity causes the clearcoat to flow.
♦ The quantity of clearcoat applied is irregular and too much on the area where the drips occur.
♦ The hardener is not suitable for room temperature. The clearcoat takes too long to harden.

When possible, it is recommended to paint the clearcoat on the piece flat rather than vertically, which greatly facilitates clearcoating and reduces the risk of drips.
♣ Corrective measures: in general it is difficult to touch up clearcoat on a partial area. It is better to apply the clearcoat again to the entire piece. To do this, carry out surface sanding to create grip over the entire piece.
Concerning the drop area, it is necessary to allow thorough drying, and this can take several days for a drop, the thickness of which can be several millimeters. Then use a mini sanding block or an eraser, with a small piece of P320 grit abrasive paper. Carry out delicate and concentrated sanding, with water, flat. The goal is to decapitate and reduce the gout. If you do not use a flat sanding block, then the sanding will not be centered on the top of the drop, and you risk going through the surrounding thickness of clearcoat.

General advice for achieving a beautiful bodywork clearcoat
This is an example showing that patience and extreme care taken at each preparatory stage and strict compliance with the application guarantee successful work. Achieving a beautiful shiny clearcoat in 20 minutes on a bodywork is therefore the visible tip of the iceberg (10%), with 90% impeccable work in the lower layers, the preparation, the cleaning of the gun, the care given to the filter. air... Then, there is this mastery of the perfect gesture which is naturally necessary to apply a flawless bodywork clearcoat (pressure, dilution, distance, angle, speed).

How to properly prepare the support?
Meticulous cleaning of the surface before clearcoating (dust, grease, silicones, humidity, sanding residue)
Use a wiping pad to remove the last of the dust
Do not touch a surface when it has been cleaned.
Ensure that the undercoat is completely dry (evaporation of solvents, drying of hydro bases).
Make sure the surface is not too hot.
Make sure that all traces of degreaser are removed.
Ensure that the surface before painting is completely dry.
Perform sufficient sanding with correct grain.
Under what conditions should the clearcoat be applied?
Ensure the correct cabin temperature (15-25°C).
Clean, dust-free room or cabin with sufficient air circulation.
Spray in low humidity conditions.
Our product advice.
Ensure compatibility with the underlays.
Use the hardener and thinner corresponding to the clearcoat.
Use the minimum dose of thinner.
Adjust the viscosity of the mixture in order to have good fluidity.
Use the hardener and thinner corresponding to the temperature.
What equipment to use and how?
Remove all moisture from pipes and compressors.
Purge your compressor and pressure regulator regularly.
Adjust your gun correctly (air pressure and jet width).
Use a thoroughly cleaned and dry gun.
Spray at the right distance, at the right speed, at 90° to the surface.

How to dry clearcoat?
Respect the correct time between the two coats of clearcoat.
Do not cook beyond the recommended time or above the recommended temperature.
Respect the drying time before delivery.

The art of varnishing