PREPARATION AND APPLICATION

Circular dents

Put a straight-edge across the dent to see if more of the panel is involved. This minor ding has depressed an area of 20in in the surrounding panel and it’s crater-shaped with raised edges. It needs dressing or it’ll consume a huge amount of filler.

Panel creases

Look along the panel. Shallow undulations that involve large areas can be tricky to put right. A well-defined crease like the one in this door is fairly straightforward. Use a straight-edge to find how much damage has been caused to the surroundings.

Swage-line dents

A swage-line adds strength to a panel, but also attracts one’s eye. A dent on a swage-line can create both high and low spots that can be confusing to put right. A repair might be smooth close-up, but the line may appear to deviate when you stand back.

Sand area

Clean the dent and surrounding area with panel wipe. Hand- or power-sand the dent and note the number of paint layers. If there are only a few, only the immediate area needs to be bare-metalled. If there are lots of layers, bare-metal the whole area.

Remove depressions

Do your best to remove depressions, leaving a shallow area to fill. Tap out the dent from the rear of the panel if you can gain access. If you can’t, use weld-on nails or glue-on tags and a slide hammer. Suction cups can be effective on larger areas.

The area to be filled needs to be slightly lower than the surrounding panel. Use a straight-edge to check for obvious high areas. A body file (pictured) can also be useful to highlight the high and low spots. Flatten high spots carefully with a hammer and dolly.

Find high spots Choose your fillers

Buy decent fillers that behave predictably and are easy to work with. On the left is a bulk filler for larger, deeper areas. In the centre is a fine filler for smaller, shallower repairs. On the right is a glaze, a very fine self-levelling skim for final smoothing.

Mix filler

Mix the hardener in the recommended ratio smoothly to avoid incorporating air bubbles. A mixing board with tear-off sheets is very useful. Temperature affects curing times, so use a little more hardener in winter and a little less in summer.

Apply filler

Make sure the area is dust-free. Wipe the spreader with a clean cloth. Scrape a quantity of filler from the edge of the mixing board. Apply it to the edge of the area and smoothly spread it across to avoid air bubbles. Repeat, overlapping a little.