Automotive
Blending technique in spot repairs
Plan the blend zone, prepare it properly and fade each coat so the new colour merges unnoticed.
Short answer
Blending means fading the colour from the repaired area into the neighbouring surface. The basecoat is applied just far enough to hide the repair, then each coat reaches a little further out and thins at the edge. The clearcoat usually covers the whole panel, so small colour differences become practically invisible.
1Why blend?
Even with the right formula, a small difference can remain between new paint and the car’s existing finish: the old paint has changed in the sun over the years, and with metallic and pearl colours the shade depends on how the paint was applied. Painting a panel edge to edge makes that difference visible at the panel line. Blending spreads the difference over a wider area so the eye does not catch it.
For the basics of colour matching, see our colour matching guide.
- Repair area
- Basecoat blend zone
- Clearcoat area
The basecoat fades out from the repair area; the clearcoat covers the whole panel.
2Plan the blend
- Mark where the repair is and how big it is.
- Decide how far the blend will reach; take it into the neighbouring panel if needed.
- Set the clearcoat boundary: in most jobs the clearcoat covers the whole panel.
- Confirm the colour and variant on a test card first.
3Surface preparation
- Clean
Clean the whole panel with a grease and silicone remover.
- Prepare the repair area
Smooth the filled and primed area with the abrasive the system recommends.
- Key the blend zone
Key the area the basecoat will spread into, and the clearcoat area, with a fine abrasive or sanding pad; clearcoat does not hold on a glossy surface.
- Mask
Mask neighbouring parts and surfaces that are not being painted; lay the tape so it does not leave a hard line.
4Applying the basecoat
Apply the first coat just far enough to hide the primed repair area. With each following coat, move the gun a little further out and turn your wrist slightly at the end of the pass to fade the paint, so no hard edge forms. With metallic and pearl colours, apply the last coat as a lighter, even effect coat.
Depending on the system, special products make blending easier: a blending thinner in some solvent-borne systems, a colourless blending base in some waterborne ones. Check the system’s TDS for which product to use and in what ratio.
5Clearcoat
Once the basecoat is fully matt, apply the clearcoat. It usually goes over the whole panel, up to a natural boundary such as a panel edge, a trim strip or a door gap. Clearcoat is blended only in narrow areas such as pillars and sills, and only with the system’s special thinner; otherwise the clearcoat edge can dull and show over time.
Common mistakes
- Not keying the blend zone enough
- Ending every coat at the same line and leaving a visible ring
- Applying the basecoat too heavily and skipping the effect coat
- Spraying the car without a test card
If you are moving to waterborne systems, also see the drying advice in our waterborne basecoat guide.
Frequently asked questions
Does every repair need a blend?
With solid colours and a formula that matches well, painting the panel may be enough. With metallic, pearl and difficult colours, blending is the safest route.
Should the blend go into the neighbouring panel?
If the repair is in the middle of a panel, the blend can often stay within it. If the repair is near the panel edge or the colour is difficult, taking it into the neighbouring panel gives a better result.
Can clearcoat be blended?
Only in narrow areas and with the system’s special thinner. On larger panels the clearcoat should cover the whole surface up to a natural boundary.
Which abrasive is used for blending?
The blend zone is keyed with a fine abrasive or sanding pad. The right grade is given in the system’s TDS.