Thoroughly degrease the bodywork before painting with paint
See the products concernedDegreasing is the quickest stage of the Preparation process and the one that causes the most defects if it is rushed.
Pits in the clearcoat, paint beading, localised peeling: in the vast majority of cases, the cause is not the paint but a surface that has not been properly degreased. A film of grease or silicone invisible to the naked eye is enough to ruin a meticulous job. This guide provides an overview of degreasing before painting, as taught to new technicians at the Carross workshop: why it is crucial, which product to use, when to apply it and which method to follow.
Key points at a glance
Degreasing involves removing all traces of grease, wax, silicone and residues before painting; otherwise, the paint will bead, form craters or peel off. A dedicated anti-silicone degreaser is used, applied before sanding and then again just before painting, using the ‘two-cloth’ method. At Carross, we recommend never skipping this two-step process: it ensures a perfectly receptive surface.
Why degreasing determines how well the paint adheres
A car body constantly carries contaminants that are invisible to the naked eye: grease from handling, protective waxes, residues from cleaning products, fingerprints, and silicones from plastic restoration or gloss sprays. All these films act as a barrier between the substrate and the paint. They are all the more treacherous because they cannot be seen or felt: a panel that looks clean to the naked eye may be entirely covered in an invisible greasy film.
The result is immediate and visible: the paint does not spread evenly; it ‘beads’ and forms craters where the contaminant has repelled it. The phenomenon is the same as that of a drop of water on a waxed car body — surface tension repels the liquid. In the longer term, adhesion is compromised and the paint peels off in patches, sometimes several weeks after the job is done, when everything seemed to have gone well.
Silicone is the worst enemy, as it migrates, spreads under the heat of the oven and resists superficial cleaning. A single trace left by a plastic polish can contaminate an entire wing. On this specific point, our dedicated guide explains in detail how to [avoid silicone contamination](/eviter-contamination-silicone) throughout the workshop, from the Preparation area to the spray booth.
Degrease before, during and after sanding
A common mistake is to degrease only once, usually just before painting. In reality, degreasing takes place at several key stages of the repair process, not just at two points.
Before sanding, degreasing is carried out to prevent surface oils from becoming embedded in the substrate during abrasion. Sanding a greasy surface merely spreads the contaminant and drives it deep into the sanding scratches, where it can no longer be removed by wiping. The contamination is then trapped beneath the subsequent layers. This initial degreasing is akin to a thorough cleaning: it prepares a sound surface for further work.
Between each preparation stage (sanding, filling, primer), an intermediate degreasing step is essential. Every operation (sanding, air-blasting, handling) redeposits contaminants: greasy dust, fingerprints, and compressed air pollution. Failing to degrease at this stage amounts to trapping these contaminants beneath the subsequent layers (Putty or Primer), which can lead to adhesion faults, micro-blistering or pitting. This intermediate degreasing is quick but systematic: it ensures each layer is properly prepared before the next is applied.
After the final sanding and just before painting, the final degreasing is carried out. This removes any remaining dust, traces of handling and surface contaminants. It is this final step that directly determines how well the first coat of paint will adhere.
Throughout all these stages, avoid touching the surface with bare hands: skin oils are one of the most common contaminants in the workshop.
Degreasing forms part of the overall preparation process described in the guide ‘Preparing a bodywork for painting’, where it is systematically carried out between each operation (sanding, puttying, primer) to ensure a perfectly clean surface at every stage.
The two-cloth method
A degreaser that has not been wiped off properly is almost as bad as not degreasing at all: as it dries, it redeposits the contaminants it has dissolved in the form of an invisible film spread across the surface. The gold standard technique — the one that makes the difference between a clean job and a paint defect — is the two-cloth method.
Apply the degreaser to a clean, lint-free cloth, not directly onto the surface. Spraying it onto the part results in an excess of product that is difficult to control: it can run, displace contaminants and accumulate in sanding scratches. If not wiped off properly, this mixture of degreaser and contaminants can become trapped in the substrate and cause adhesion faults or craters in the paint.
Work in small areas, small enough to be wiped down immediately. The first cloth, lightly dampened, is used to dissolve and lift contaminants with a steady, controlled wiping motion. Without delay, before any evaporation occurs, wipe with a second clean, dry cloth to collect the residues and remove them from the surface.
Three rules ensure the method is effective. Firstly, wipe using a linear motion, ideally in criss-cross strokes (horizontal then vertical), to avoid missing any areas. Secondly, change the cloth regularly: a saturated cloth no longer cleans; it simply smears. Finally, never allow the degreaser to dry on its own on the surface — this is when contaminants redeposit and can cause defects such as craters or adhesion problems.
Working in small, successive areas is key: it is better to make several controlled passes than to apply the product over too large an area, which is impossible to wipe down properly.
Which degreaser to choose depending on the surface
Not all degreasers are the same, and the choice depends directly on the surface and the stage of the work. Using the wrong product, even with the right method, can cause defects that remain invisible until the paint is applied.
There are two main, complementary categories. Anti-silicone solvent-based degreasers form the basis of bodywork: they dissolve grease, wax and silicones whilst evaporating without leaving any residue, provided they are wiped off properly. Water-soluble degreasers (known as ‘hydro’ degreasers), on the other hand, target contaminants that solvents struggle to remove: salts, sweat, hydrophilic residues or certain types of atmospheric pollution.
Using both is often necessary to achieve a reliable result. The water-soluble degreaser is used first to remove water-soluble contaminants, then the solvent-based degreaser completes the cleaning process by removing fatty substances. Reversing this order simply spreads certain contaminants without removing them properly.
On bare sheet metal, care must be taken with the choice of product: some degreasers that are too aggressive or not wiped off properly can leave marks or promote flash corrosion. A product suitable for use on metal should be chosen, and over-application should be avoided.
On primer, the level of care required depends on its condition. A perfectly dry primer can withstand standard degreasing, but a recent or poorly cured primer may be softened or damaged by solvents that are too strong. Degreasing must be light and controlled.
On old paintwork or blending areas, this is a critical point that is often underestimated. Certain degreasers can reactivate buried contaminants or soften old layers, which may lead to defects such as silicone bleed-through, curling or adhesion problems.
On plastics and elastomers (bumpers, wing mirrors), a degreaser specifically designed for plastics should be used, ideally one with an antistatic effect. Conventional solvents can attack the material, cause it to swell or leave marks. Application must be light and controlled.
The evaporation rate must be suited to the situation: • a product that evaporates too quickly does not allow enough time to work properly • a product that evaporates too slowly increases the risk of streaks and redeposited contamination
The right choice therefore depends as much on the surface as on the nature of the contaminants to be removed.
Why avoid ‘homemade’ degreasers
The temptation to use white spirit, acetone or a recycled solvent is understandable — these are often what we have to hand. It is also a false economy. These products frequently leave a residual film which itself becomes a contaminant, attack certain primers or plastics, and lack the anti-silicone properties of a bodywork degreaser formulated for Paint.
Acetone, in particular, is very harsh on plastics and can soften fresh primer. White spirit leaves an oily film that impairs adhesion. As for recovery solvents, by definition they are already laden with whatever they have dissolved elsewhere. A dedicated anti-silicone degreaser is designed to evaporate cleanly without leaving any residue and to be compatible with Paint systems. For a repair that you want to last, it is the only sensible choice.
Mistakes that ruin the degreasing process
Even with the right product, certain habits can ruin the result. The most common mistake is allowing the degreaser to evaporate on its own, which turns the cleaning process into a simple re-deposition of contaminants. Next comes wiping with a cloth that is already contaminated, or worse, a lint-shedding cloth that leaves fibres in the paint mist. Touching the surface with your bare hand after degreasing negates the process in the area touched. Blowing with unfiltered compressed air redeposits a fine mist of oil from the compressor. Finally, degreasing just once — either only before painting, or only before sanding — leaves the door open to contamination on each occasion. Degreasing is quick, but it does not tolerate a slapdash approach.
How to choose
- Type of product | opt for a dedicated anti-silicone degreaser for bodywork, not a generic solvent - Plastic or elastomer surfaces | check that the degreaser is compatible with plastics before application - Application | use clean, lint-free cloths; never use a cloth laden with residue - Evaporation rate | adapt to the size of the areas being treated so you can wipe them down before the product dries - Homemade solutions | avoid these: they leave a residual film and lack sufficient anti-silicone power - Carross’s tip | work in small areas so you can always wipe it off before the product dries
The tip that makes all the difference
Never spray directly onto the part
It is a very common mistake, even amongst some professionals: applying the degreaser directly to the surface. In reality, this practice creates more problems than it solves.
When sprayed onto the part, the degreaser penetrates the micro-scratches left by sanding. However, once lodged in these imperfections, it becomes difficult, if not impossible, to wipe off properly. The result is that residues remain trapped beneath the paint, which can lead to adhesion faults, contaminants rising to the surface or undesirable reactions during application.
The correct method is simple and much safer: apply the degreaser to the cloth, never directly onto the surface. This allows you to control the amount of product used, avoid saturating the surface and ensure effective wiping.
This detail may seem minor, but it often makes the difference between a clean preparation and a problematic paint job.
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FAQ
Which degreaser should I use before painting?
A silicone-removing degreaser specifically designed for car bodywork. It dissolves grease, Wax and silicone without leaving a film and is compatible with primers and paints. Avoid using generic solvents (white spirit, acetone) as these leave residues or can damage certain surfaces.
How do you degrease a car body before painting with paint?
Degreasing is not limited to a single final step. It is carried out throughout the Preparation process: before Sanding, then after each stage of work, and finally just before painting. The method remains the same: • apply the product to a cloth (never directly onto the part) • work in small areas • wipe off immediately with a second clean cloth. Wipe in one direction only, without going back over the same area, and change the cloth as soon as it starts to become soiled. Some technical data sheets specify evaporation times or the application method: you should refer to these, particularly with sensitive systems. The aim is not to wet the surface, but to remove contaminants without spreading them.
Which degreaser should be used before painting on bodywork that has already been primed with Primer?
On primered surfaces, stick to a suitable bodywork degreaser, used with even greater care. The idea is not to ‘wash’ the surface, but to remove sanding dust and contamination from handling. Apply lightly with a cloth, without soaking the surface, to avoid any interaction with the primer (swelling, marking or solvent bleed-through). The technical data sheet is essential here: certain primers or paint systems require specific degreasers or precise application conditions.
How do you degrease an elastomeric component or a bumper before painting?
Use a suitable bodywork degreaser (a degreaser specifically designed for plastics, ideally with an antistatic effect) and take even greater care when using it. Plastics are sensitive: • use a compatible degreaser • avoid applying too much product • work quickly and neatly. Always apply to a cloth; never spray directly onto the surface. It is essential to check the technical data sheet for compatibility with plastics and elastomers: not all degreasers are suitable. Once clean, adhesion will be ensured by a suitable plastic primer.
Can a ‘homemade’ bodywork degreaser replace a specialist product?
No, not for a job that needs to last. Homemade solutions (white spirit, acetone, recycled solvents) often leave a film, can damage plastics and primers, and lack the necessary anti-silicone properties. A degreaser formulated for paint evaporates cleanly and remains compatible with the systems applied afterwards.
Updated: 16/07/2026
Check out our bodywork guides and tutorials. The Carross Tech’Team: +33 (0)1 60 27 20 19.
