Automotive body filler and putty
Shape a repair with the right filler, substrate preparation and curing process instead of treating filler as a structural repair.
Filler restores surface contour
Body filler, often called putty, is used to build and refine the contour of a suitable repair area before refinishing. Metal repair deals with the underlying panel shape; filler addresses the remaining surface profile within its approved limits.
Filler is not a substitute for repairing structural damage or an unassessed rust hole. A smooth painted surface alone does not establish that the underlying repair was appropriate.
Different products do different jobs
Two-part polyester fillers mix resin with a specified hardener and have a limited working time. Finishing glazes and spot putties address smaller imperfections, while epoxy and plastic-repair materials have their own intended applications. One-part and two-part products are not interchangeable.
Do not treat a generic category name as permission for steel, aluminium, composites and flexible bumpers alike. The product’s permitted substrates and the repair system determine suitability.
Bare metal is not the only possible substrate
Some fillers are approved on properly prepared metal, some on specified cured coatings or primers, and some across several substrates. Certain repair procedures call for epoxy primer before filler. The statement that filler must always precede every primer is therefore unsafe as a universal rule.
Check the filler and paint-system instructions together for substrate, cleaning, abrasion and curing conditions. Do not assume an etch primer and epoxy primer are equivalent. Rust, loose coating and contamination must be addressed rather than buried.
Mix and apply within the product’s limits
Measure the prescribed hardener ratio and mix on a clean suitable board using the stated method. More hardener does not create a universally stronger repair. Mix only what can be used within the working time, and do not return activated material to the supply container.
Apply in the specified layers and remain within the maximum permitted build. Excessive thickness and trapped air can create problems, but the permitted amount and cure are product-specific. Material that has begun to set should not be revived by adding thinner or fresh filler.
Cure, shape and inspect before paint
Wait for the specified sanding condition. Use the recommended abrasive progression and suitable blocks or tools to preserve the panel contour. Inspect for pinholes, low areas and remaining scratches with suitable lighting and, where appropriate, a guide coat. Touch is a useful check but not the only one.
Dust control and the specified protective equipment are part of sanding. Follow the material’s wet or dry restrictions. Once the surface is correct, continue with the compatible undercoat and paint sequence; a polished-looking filler repair is not a completed exterior finish.