How to Prepare the Surface Before Painting

Painting itself is only the final step. The real quality of the finish is determined by preparation: correct sanding, degreasing, suitable primers and fillers, and respecting the required flash-off and drying times. Below you will find a clear process and practical quick tips for working with both spray cans and spray guns.

1) Assess the surface and remove old paint if needed

Goal: a matte, solid and clean surface without wax, silicone or loose paint residues.

• Matting the original paint: in many cases it is enough to remove gloss and surface defects. New paint will not adhere properly to a glossy and smooth surface.
• Complete paint removal is necessary for unknown or reactive paint systems, old repairs or poor adhesion. Options include mechanical sanding, chemical paint remover, professional chemical stripping or blasting.
• If you sand through to bare metal, do not leave the surface exposed. Seal it as soon as possible with epoxy primer.

2) Degreasing and sealing the surface

• Degrease thoroughly before sanding and after sanding to remove sanding dust and contaminants. Use a silicone remover / degreaser and allow it to flash off for a few minutes.
• Epoxy primer is recommended for bare metal and problematic substrates. Epoxy primer helps prevent corrosion, evens out absorption and blocks possible reactions with residues of old paint layers.
• Plastic parts: on unpainted or new plastic parts, use a plastic adhesion primer, such as plastic primer, before continuing with the next steps.

3) Repairing uneven areas with filler

• For larger damage or areas where material is missing, use fibreglass filler. For standard smaller repairs, levelling and final shaping, use universal polyester filler.
• A common example is an alloy wheel scraped against a kerb during parking. For this type of smaller local repair, aluminium filler is a simple and affordable solution for DIY repairs.
• Apply filler with a flexible spreader in thinner layers and shape the hardened material gradually, typically P80–P120 → P180–P240.
• Carefully feather the edges of transitions so they are not visible after painting.

4) Filler primer – levelling small imperfections

Filler primer spray is a practical choice for smaller repairs and standard surface preparation. It helps level micro-defects, approximately up to 0.5 mm, and creates a smooth, evenly absorbing surface ready for paint. For larger areas or spray gun work, a spray gun filler primer version can also be used.

• Drying: approx. 24 hours when air-dried.
• Sanding: wet sanding P400 → finishing with P600–P800.
• Filler primer is absorbent – do not store finished parts for a long time only in filler primer. For longer storage, keep the part sealed with epoxy primer.

5) Final preparation before paint

• Lightly matt the entire surface with Scotch-Brite, using the correct type for the chosen paint system, and check that no glossy spots remain.
• Carefully remove dust, degrease with silicone remover, allow it to flash off and wipe the surface with an antistatic tack cloth.
• The surface is now ready for basecoat, effect paint or clear coat.

Quick reference

• Filler shaping: P80–P120 → P180–P240
• Filler primer sanding: P400 → P600–P800 for basecoat / effect paint
• Bare metal: seal with epoxy primer as soon as possible
• Plastic: use plastic adhesion primer

Surface prepared? Now the actual painting can begin.