How to apply bodywork varnish?

The exterior finish is the first thing a person sees when looking at their vehicle. The quality and durability of car and bodywork varnishes is a reflection of the quality of the vehicle itself.

Shine and durability:
The varnish is the layer that forms the last interface with the environment. It includes the greatest share of performance and chemical and technological innovation. Automotive varnish must be able to withstand weather conditions, fuels, sun, heat, bird droppings, abrasion, detergents and washes, without losing its shine...

Tutorial: how to varnish your car and its bodywork?

Find detailed instructions for each step below:

Step 1 ► Preparing the support
Step 2 ► Mixing the varnish
Step 3 ► Applying the varnish with a gun or aerosol
Step 4 ► Drying

Types of bodywork varnish for car, motorcycle, bicycle

Today, all varnishes, or almost all, in the current state of knowledge and the chemical industry, are 2C polyurethane solvent-based acrylic varnishes.
Cellulosic varnishes have long been abandoned, epoxy varnishes cannot withstand the sun and water-based varnishes are not up to the task. Solvent-based acrylic varnishes have clearly dominated the market for around thirty years, thanks to their qualities, their resistance to abrasion and the sun, as well as their shine.

Today, here are the varnishes mainly used:
- UHS rapid varnish: for touch-ups, without baking and to ensure rapid turnover of vehicles in workshops.
- Classic UHS varnish: for complete or partial painting, for all types of vehicles.
- Spray varnish: for individuals who do not have equipment.

We do not include in this list varnishes sold in mainstream stores because they are not professional and reliable products.

♦ P500 abrasive sheets
♦ Degreaser
♦ Sticky stamp

Step 1 ► Preparing the support

The final stage of bodywork painting is a crucial and delicate stage. Maximum care must be taken when preparing the support.

Sand
This starts with sanding, unless the paint is covered with varnish immediately “wet on wet”.

Sanding must be done with P500 grit abrasive paper.
This concerns most varnishes, and this indisputable instruction is given in the varnish technical sheet. There are certain varnishes with a high solids content, for which the technical sheet recommends sanding with P320 grit sandpaper.

It is possible to sand with P600, P800 or P1000, however this does not give better results in terms of shine, and this in fact cancels any guarantee of good adhesion and durability over time.

Degrease
If the surface has been exposed to contaminants or simply to the open air for any length of time after sanding, it is possible that the paint surface may be contaminated. This can be invisible dirt, grease, silicones, and all these contaminants are likely to cause defects that will appear on the freshly applied varnish.

The degreaser is a harmless solvent for paints, which is applied with a paper cloth to the surface.
⚠ It is important to pick up the degreaser with another dry, clean paper without waiting for the degreaser to evaporate or become encrusted on the paint!

Dust off
Just before spraying the varnish, the painter must remove dust from the surface. This is done with the gun, by blowing air onto the surface. And also by passing a sticky pad over the paint, with the weight of the hand, without pressing, to collect the last dust.

It is also useful to take more precautions to the point of blowing out the entire painter's suit, using the gun or a blower.

♣ How to use the sticky pad? Many people do not use it correctly. The tampon should be completely unfolded and then gently crumpled into a ball before using it. This pad is not designed to collect large quantities of dust, particularly sanding residue. It is a delicate pad which is very effective in collecting the last remaining and light dust. After use, fold it carefully and store it in its bag so that it does not dry out.

Step 2 ► Mixing the varnish

Bodywork varnishes are two-component products, the hardening and drying of which are ensured by a chemical reaction between the varnish and the hardener.
The painter must only mix the quantity of varnish he will need, because the mixture made can only be used for 30 to 60 minutes.

Most automotive polishes mix in a 3:1 or 2:1 ratio.
These indications refer to the proportion of varnish compared to the proportion of hardener.
Here are a few different examples:
3:1 → 300 g of varnish + 100g of hardener
3:1 → 600 ml varnish + 200 ml hardener.
2:1 → 1L of varnish + 0.5L of hardener
2:1 → 200g varnish + 100g hardener

How to make an exact varnish mix?

To make a correct mixture, you must first refer to the technical sheet. We only look at the mixing instructions, which are given according to volume (in ml) or weight (g). The greatest precision is naturally achieved when mixing with a weighing scale. It is not absolutely important to have perfect accuracy, and an approximation margin of up to 5% with the recommended mixture is acceptable without major problems.

Stir with a ruler in a figure 8 motion, then let sit for 5 minutes.

How to use a graduated mixing cup?

It is possible to use a graduated measuring cup. There are 600ml or 1400ml bodywork cups which are printed with graduations for 4:1, 3:1, 2:1 or even 1:1 mixtures... and this allows mixing without a scale.

1 → Refer to the mixture marking which corresponds to its varnish (example: 3:1)
2 → Fill the portion of varnish up to the “3” mark
3 → Add the proportion of hardener up to the “1” mark

The thinner
Dilution is always suggested rather than imposed. The dilution can be free and variable depending on the size of the nozzle.
Of course you should not add too much thinner, as this can increase the risk of running, and also affect the level of shine. The rule is to add only the minimum portion of diluent. The dose of thinner is generally measured according to the quantity of varnish (hardener not included).

“Pot life”
Here is an English term that is often found in the painter's vocabulary: it concerns the lifespan or use of the mixture, during which it is possible to use the varnish. Beyond this time, the varnish becomes too thick and begins to harden, it can no longer be used. Particular attention must be paid to the use time of the varnish, especially when it is a rapid type varnish, and more so when the ambient temperature is hot.
A varnish should be used 5 minutes after mixing, and generally before 30 minutes.

Step 3 ► Applying the varnish with a spray gun or aerosol

It is possible to find different instructions on the labels, on the technical sheet or on the internet page of a bodywork varnish. These instructions are sometimes completely different from each other: shade of coats, suggested thickness, weight per square meter, etc. All these data designate the quantity of varnish that the painter must apply to the surface.

A little theory
To achieve a beautiful shiny varnish, the essential point is to deposit the right amount on the paint:

→ If too little varnish is applied, then this varnish will not be able to level and smooth itself properly. In addition, insufficient thickness will constitute insufficient protection.

→ On the contrary, if too much varnish is applied, then initially runs will occur, and then a loss of shine is likely to occur. On the other hand, it is interesting to note that too much thickness weakens the paints and increases the risk of peeling or cracking.

The right thickness for a varnish is around 50 µm dry, which represents around 2 coats.

Some modern, high quality varnishes (UHS) contain less evaporable solvent and more solid matter: for these varnishes manufacturers sometimes recommend applying ½ coat, then a full coat, which ultimately creates a thickness of 50µm dry.

Spraying the varnish

The success of a glossy varnish essentially depends on the quantity of varnish deposited on the surface. It is also important to work in a dry atmosphere with a temperature of 15 to 25°C. It is possible to work in cold weather or in hot weather with special hardeners that we offer.
Here are the practical tips for successfully applying your bodywork varnish:

Set the gun pressure to 2.5-3 bar, and open the spray angle to maximum. Press the trigger completely to spray as much product as possible. The method of application with an aerosol is quite similar to that of the paint gun. The aerosol must have a flat jet nozzle.

Apply a medium coat, then wait 7 to 10 minutes before applying a second coat. This second and final layer must be perfectly shiny. Never spray 3 coats.

1 ► Keep the gun 15 cm from the surface
2 ► Always keep the gun perpendicular to the surface: keep your wrist flexible to follow all the shapes or contours of the bodywork.
3 ► Ensure a stable movement speed, adjusted to deposit enough products. If the gun moves too fast, it cannot spray enough varnish, and on the contrary, if it moves too slowly, it deposits excess varnish.
4 ► Always paint from left to right, then from right to left, overlapping each layer by 50%.
(image overlay of layers)

Step 4 ► Drying

Most varnishes are designed to polymerize, dry and harden at room temperature (Around 20°C). Some quick polishes can dry in 45 minutes while most regular polishes cure in 12 to 24 hours.

It is important to protect the varnish from dust and humidity while it is drying.

Drying the varnish is broken down into several stages:

*Excluding dust: this is one of the first early stages of drying the varnish, more precisely the time from which dust will no longer be able to stick to the varnish.

*Dry to the touch: This is the time limit from which it is possible to lightly handle or touch a part.

*Dry completely: this is the time from which the varnish is considered dry.

*Commissioning: this is the period from which the vehicle or object can be driven or used. It’s not much different from “dry to the core”.

*Complete and optimal hardening: this is an extended period (generally several days) where the varnish has reached its maximum hardening.

Forced cooking or drying
The hardening and chemical polymerization reaction of the varnish can be accelerated thanks to a higher temperature. This is not necessary to obtain a beautiful varnish. This makes it possible to increase the output of professional painters, and the rotation of parts in the workshop, with faster provision of the vehicle to the customer.

Whether cooking in the oven (at 40-60°C) or drying with infrared lamps or even ultraviolet lamps, it is important to respect a desolvation period before cooking.
* desolvation: around ten minutes are necessary to allow the varnish solvents to escape and evaporate. When this time limit is not respected, the surface layer of the varnish closes, and solvents become trapped in the varnish film. This is the main cause of the micro-bubbling defect.

Types of bodywork varnish

Numerous developments have led to two-component High Solid varnishes.
The BS finishing varnishes offered by StardustColors are all 2-component HS or UHS automotive varnishes with superior characteristics, with exceptional hardness, and very high “wet effect” glosses. They also offer excellent drying speed and very good polishing ease.

A high quality varnish must have a good thickness as well as a strong glossy lacquered effect. But it must also prove its resistance and durability over time. This is why StardustColors BS varnishes have been proven and successfully tested under extreme conditions: in extreme cold in Russia, just as in Greece, with high temperatures and maximum UV exposure.

We offer acrylic varnishes in particular.

What are the best car polishes?>

Here is a ranking of current automotive varnishes:
LS: Low Solid / MS: Medium Solid / HS: High Solid / UHS: Ultra High Solid

Bodywork varnishes and their hardeners:

The car varnishes offered by StardustColors offer a great advantage: They offer a range of 3 speeds of hardeners and thinners, in order to adapt to each temperature condition, and also to the size of the parts to be varnished:

Winter: From 5 to 15°C: Rapid hardener and thinner

Intermediate: From 15 to 25°C: Normal hardener and diluent

Summer: From 25 to 35°C: Slow hardener and thinner

The application:

There are varnishes to be applied in 2 coats and specific single-coat varnishes (such as UHS varnish).
Single coat varnishes should normally be applied in one thick coat. As for conventional varnishes (such as HS auto varnish), those are applied in a first coat of normal thickness with a slightly diluted mixture, in order to create a non-smooth adhesion surface. In the correct time (between 5 and 20 minutes depending on the temperature and the type of hardener), the 2nd final coat is applied: This must be wet and thick, and create a smooth surface with a "mirror" appearance when it dries, without running. thanks to the first layer which is irregular and which will have slightly "set" during 5 to 20 minutes.

Applying a varnish is delicate and requires a certain amount of handling of the varnish, but above all scrupulous respect for the care of preparation and application. Many faults can occur:
Holes, micro air bubbles, marks, runs, orange peel, lack of gloss, peeling

Here are the tips to avoid all these defects:

• Meticulous cleaning of the surface before varnishing (dust, grease, silicones, wax, sanding residue)

• Use a wiping pad to remove the last 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

• Ensure that all traces of degreaser are removed

• Ensure that the surface before painting is completely dry

• Ensure compatibility with underlays

• 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

• Use the hardener and thinner corresponding to the varnish

• Use the correct dose of hardener and thinner

• Adjust the viscosity of the mixture in order to have good fluidity

• Use the hardener and thinner corresponding to the temperature

• Ensure the correct cabin temperature

• Spray at the correct distance from the surface

• Spray under normal humidity conditions

• Respect the correct time between the two coats of varnish

• Keep the varnish away from water while drying

• Respect the drying time before delivery

• Do not dry by ventilation

• Perform sufficient sanding with a fine grain

Polishing and buffing:

StardustColors offers a complete line of abrasive papers at wholesale prices for professionals. Exclusive and ultra-fine grades for polishing will be offered: 2000, 3000 and even 5000!

Special car varnishes to discover:

StardustColors Matte Varnish
Les vernis Candy
Spray varnish

UHS varnish
MS varnish
Vernis HS
Quick drying varnish
Bodywork varnish spray
Ceramic varnish
How to maintain the shine of a bodywork varnish?