How to touch up bodywork paint in 7 steps?

In a simple tutorial intended for unqualified people who wish to repair bodywork paint for the first time, we present in 7 steps, all the instructions for retouching a paintwork:

Step 1 ► Sand the surface
Step 2 ► Apply putty then sand
Step 3 ► Demarcate the area and mask
Step 4 ► Apply primer then sand
Step 5 ► Apply paint
Step 6 ► Varnish and melt
Step 7 ► Polish and buff

All the steps for touching up car or motorcycle paint are described in detail below.

Before that, here are the details of the products and tools to have, but also of the work space to prepare, to be able to begin the paint touch-up work.

List of consumables and tools for retouching a bodywork

1 Abrasive papers: grit 220, 320, 500: for the different phases of sanding putty and primer
1 Sanding block: to sand flat and efficiently
1 Putty Spatula (only if using putty)
1 Sticky pad: to collect dust before varnishing
1 paint gun (any nozzle is suitable, between 0.8 and 1.4 mm)
1 Paper masking adhesive 24 or 48mm 
1 Respiratory mask

List of products for refinishing bodywork:

Degreaser
Cleaning thinner (unless painting with aerosols)
Putty (useful only in case of deformation, or very significant scratches)
Primer
Paint: Original color of the vehicle obtained using the color code
Varnish

Most products are available in aerosol or pot on our site, do not hesitate to ask our technical department for advice (tech@stardustcolors.com)

The work area for retouching a bodywork:

To protect yourself from fumes, work in a properly ventilated area, that is to say with sufficient air circulation (inlet and outlet) to quickly evacuate paint fumes during spraying.
Choose a clean, dust-free and sufficiently bright work area. It is possible to wet the floor and walls to “catch” residual airborne dust.

How to touch up bodywork paint?

When considering refinishing a bodywork following a scratch or impact, it is important to take the time to examine the extent of the damage in order to be able to choose and plan the necessary steps and the necessary products.
⚠ You must naturally limit yourself to the essential steps, with the minimum of work and the minimum of products: all the steps are not always necessary depending on the case.

Step 1 ► Sand the surface

The first step in refinishing a bodywork consists of sanding with an abrasive sheet: this will allow the products to stick to the surface and will guarantee us against any detachments and defects of poor resistance over time.

→ If you have to apply a putty, you must sand with P220.
→ If a primer must be applied, sand with P220 or P320.

⚠ Sanding must be light and superficial, because it is not a question of stripping, nor of removing the paint and even less the different layers present on the bodywork.

It is possible to sand with water or dry sand.
Before proceeding to the next step, apply degreaser with a sheet of paper and clean the surface well.

Step 2 ► Apply putty then sand

♣ In most cases of bodywork refinishing, it is not necessary to apply a sealant.

This step consists of applying a thick layer of putty to restore the surface condition following deep scratches or the presence of dents or impacts.
→ A putty is applied when the defect is greater than ½ mm deep.

We have written a tutorial on using putty.

The putty allows adhesion directly to the metal, that is to say the sheet metal of the vehicle, if it is partially or completely exposed.

The putty is used with a red hardener which is dosed at approximately 2%. The putties, once mixed with their hardener, must be “worked” very quickly (in less than one to two minutes) because they harden very quickly and they must therefore be applied immediately to the surface and smoothed with a spatula.
⚠ It is important to make a clean application, as the more excess filler there is, the more time will be spent sanding.

The putty can be sanded with P220 paper, then P320.

Step 3 ► Delineate and mask the retouch area

Before going any further with spraying paint products, it is important to protect the surrounding surfaces and areas of the bodywork, which are not affected by the paint touch-up.

As a general rule, it is always advisable to paint a complete part and avoid painting a partial surface: a part represents for example a hood, a door, a wing.

⚠ Masking adhesives should never be put on the central area (red dotted lines) of the painting: this would result in creating a clearly visible demarcation.
⚠ It is not wise to paint the room completely, that is to say all the way to the ends: the subtle difference in color or tone will be more visible with a clear demarcation.

When the area of the scratches is relatively small, it is advisable to paint only the area of the scratches, fading or blending with the original color present on the part.
It is therefore necessary to apply protection with adhesive masks all around the entire part (red box). The entire part must first be sanded with P500. Only the center of the room needs to be primed and painted. And the whole piece needs to be varnished during the final stage.
Paint touch-ups should be avoided as much as possible, including the partial application of varnish. This is possible and requires a special technique explained in step 7.

Step 4 ► Apply primer then sand

It is advisable to use a primer, even when there are no scratches. However, when the surface is perfectly smooth and it is simply a matter of touching up the color, it is possible to skip the priming step, applying the paint directly. In the case of pearlescent paints, it will be necessary to go through the priming stage, because they are rather transparent paints with little coverage.

Utility :
The primer creates a perfect surface, filling in very fine irregularities, small holes, scratches and slight unevenness. It also allows you to create a medium gray and homogeneous background.
When a putty has been applied, it is obligatory to go through a priming phase: it is not possible to apply paint on a putty.

One coat of primer is equivalent to 0.05 mm, or 50 microns minimum.
Depending on the condition of the surface, it may be necessary to apply one coat to three coats of primer.

Appearance :
Primer is a paint-like product that has a thick, yet lightweight texture that makes it easy to sand.
It is a product usually delivered in a gray color: for bodywork paint, RAL GRAY 7035 (light gray), 7040 (medium gray), 7016 (dark gray) are generally used. Each automotive tint must be applied to a specific gray reference.

Instructions :
Apply one or more coats of primer (5 minute intervals)
Allow thorough drying (2 to 4 hours at 20°C)
Sand with P320 then P500
It is important to remove as much of the total thickness of the primer as possible, without cutting through.
Observe and touch with the palm of your hand to detect the presence of surface defects.
Degrease

It is possible to use a sanding guide to know if you need to sand more or if you have sanded enough.

Step 5 ► Apply Touch-Up Paint

The surface is ready to paint: it is clean, smooth and degreased.
A few seconds before painting, all that remains is to pass the sticky pad over the surface to collect the last dust that may be present.

The paint must be mixed according to the instructions and must be used "ready to use", with the aerosol or paint gun.

Advice !
♣ Multiple layers are needed to cover the bottom. It is better to apply more thin coats, rather than thick coats. Always apply the layers from left to right, allowing sufficient drying time of a few minutes, depending on the ambient temperature, between each layer.

♣ Whether you paint with an aerosol or a paint gun, the secret to a successful touch-up of paint lies in a very flexible wrist movement.

If possible, create a blended effect application with the original color.

After application, a visual difference can be seen between the fresh, slightly glossy coat in contrast to the matt, sanded base coat.

⚠ A degreaser should not be applied to fresh paint when applying varnish directly afterwards.

Step 6 ► Varnish and blend: Final step for bodywork refinishing

The varnish must be applied quickly after painting, simply to benefit from a natural cohesion between the fresh paint and the varnish. Beyond 30 minutes at a temperature of 20°C, adhesion between paint and varnish is no longer guaranteed, without sanding. Sanding should be avoided when pearl or metallic paint has been applied.

The varnish must be applied to the entire piece, always in 2 glossy coats, with an interval of 10 minutes between each coat.

► The secret of a successful varnish lies in the “right” quantity of product deposited on the paint and therefore, you must monitor these two points:
♦ Distance between gun or aerosol and paint
♦ Stable movement speed

Can we apply varnish to a partial area?

This is not recommended, but it is sometimes necessary to save money on large parts (like a roof or a bumper). In order not to obtain a visible halo around the shiny varnish freshly applied to the old varnish, some painters use a “Blender”, which is an aerosol solvent, which allows the integration and blending of freshly painted paint over an old paint area.

Always remember to remove masking adhesives before the varnish is completely dry.

Step 7 ► Polish and buff, in case of micro defect

Whatever the application conditions and the cleanliness of the paint workshop, it is impossible to guarantee a flawless varnish, without the presence of dust, an insect, a hair or a small grain. .. It is easy to correct superficial defects in a varnish by polishing.

We have made a complete tutorial on the polishing technique available on our site.

Wait 24 hours to ensure the varnish is completely dry.
Sand with 2000 then 3000 grit and a little water to remove the defect.
With a polishing paste and a sheepskin, polish the varnish. The speed of rotation and the rise in temperature allow the shine to be recreated.
Finish polishing with black foam.

All products relating to polishing, with foam discs, foam, polishing paste and polishers are available in our polishing category.

The quantity to plan for a touch-up

An aerosol of paint, primer or varnish allows you to cover in several layers an area of up to 0.5 m² (i.e. a rectangle with a length of 1 m by a height of 50 cm ).

To touch up a bodywork on an area of approximately 1 m² maximum, it is necessary to provide at least 250 g or 250 ml of ready-to-use paint and the same quantity for the primer and varnish.

→ If you have a gun, then choose the option of potted products.
It is not at all wise to opt for the spray paint option: paint cans generally contain a significant portion of propellant gas in the total volume advertised. This means that an aerosol advertised as 400 ml usually contains 100 ml of paint for 300 ml of propellant.

How to repair a complete bodywork painting
How to polish and shine bodywork paint?