1 · What is happening at this step
Primer-surfacer is levelled into a uniform, scratch-free surface that the basecoat can be applied onto. This is the step where the final surface texture of the panel is decided: whatever scratch depth remains here has to be covered by the coats that follow, and if it cannot be covered, it will be seen.
[TO CONFIRM: image — process photograph of primer sanding with guide coat visible, own material or authorised only, registered in ../assets/_manifest.md]
2 · What usually goes wrong
Cut-through. The primer film is thin, and it is thinnest exactly where the tool concentrates: crown lines, panel edges and the high points of a repair. Once you cut through to filler or bare metal, the area has to be re-primed. Cut-through comes from pressure and from a firm backing pad far more often than from a grit that is too coarse.
Sand scratches show through the topcoat. The scratch left at this stage has to be shallow enough for basecoat and clear to flow over it. If the final grit is too coarse, or a rung of the ladder is skipped, the scratch swells back and appears as fine lines in the finished panel — most visible on dark solid colours, and most visible in sunlight, which is exactly where the customer looks.
Loading on soft primer. Two-component primer-surfacer is comparatively soft and loads an abrasive quickly, particularly when it is sanded before full flash-off or cure. Loaded abrasive stops cutting and starts polishing, which leaves a surface the basecoat will not grip evenly and which can show as a difference in colour or texture.
Water left behind after wet sanding. Water sits in the scratch pattern and wicks into porous filler edges and into any cut-through. If it is not fully dried, it returns later as blistering under the clear coat — weeks after the car has been delivered. Wet sanding also makes it harder to judge how much material is actually being removed.
A patchy scratch pattern gives a patchy colour. Mixed grits on one panel, or hand sanding next to machine sanding, produces inconsistent surface texture. On metallic and pearlescent colours that inconsistency reads as mottling or a shade difference, and the complaint is usually aimed at the paint rather than at the abrasive.
3 · What this step uses
POLIRITE M-Series — abrasives for primer-surfacer levelling
[TO CONFIRM: series designation pending finalization]
Intended for dry and wet sanding of two-component primer-surfacer, with an emphasis on consistent scratch depth and on resistance to loading on soft films.
- Formats supplied: [TO CONFIRM: which of disc / sheet / roll / sponge-backed abrasive are actually available]
- Dry sanding or wet sanding: [TO CONFIRM: which of the two the range supports]
- Abrasive grain: [TO CONFIRM: available grain types]
- Grit range: [TO CONFIRM: available grit range, and whether P-grade or CAMI]
- Backing: [TO CONFIRM: paper weight, film or foam backing options]
- Anti-loading treatment: [TO CONFIRM: whether a stearate / anti-loading coating is applied]
- Disc diameters: [TO CONFIRM: available diameters in mm]
- Hole patterns: [TO CONFIRM: dust extraction hole patterns and hole count]
- Attachment: [TO CONFIRM: hook-and-loop or pressure-sensitive adhesive]
- Recommended grit ladder for primer work: [TO CONFIRM: ladder to be confirmed with the factory, do not state a typical ladder as ours]
Accessories used at this step
- Soft interface pads for contours and edges: [TO CONFIRM: whether supplied, and available thickness]
- Sanding sponges and flexible abrasives for mouldings: [TO CONFIRM: whether supplied, and available grits]
Supply terms for products on this page
– MOQ: [TO CONFIRM: MOQ per format]
– Lead time: [TO CONFIRM: lead time in days after receipt of deposit]
– Packaging: [TO CONFIRM: pieces per box, boxes per carton, carton dimensions and weight]
– Customisation: [TO CONFIRM: private label, custom sizes and custom hole patterns]
– Samples: [TO CONFIRM: sample policy for this range]
[TO CONFIRM: image — product close-up, in-use photograph and packaging photograph for each series above, own material or authorised only, registered in ../assets/_manifest.md]
4 · Request a quote
Tell us whether you sand dry or wet, the primer system you use, the final grit you run today and the machine it runs on.
Button: Request a quote → /contact/
Form prefill hint: Dry or wet sanding · Primer type (2K HS / MS / other) · Current final grit · Machine type and pad · Monthly usage