Carefully fill the bodywork

Small bumps, rust bubbles or even small rust holes - the reasons to fill a body are manifold. In addition to the choice of a suitable filler, it is also the preparation of the body when filling the body, which have enormous impact on the result. Especially medium to long term. Here we provide a detailed manual for filling a bodywork.

Basically before filling the bodywork

There are many different fillers. In the paint shop in particular, different filler materials are often required because, depending on the product, the spatula absorbs water, closes too much water with high filler layers or can not be applied to every primer. For the own filling of the body 2K polyester putty is the optimal choice. This allowed thicker layers to be applied in several steps.

The preparatory work decisively determines the final quality

In addition, 2K polyester putty can also be easily sanded. But before filling the body, the focus is on the preparation. Rust must really be one hundred percent removed, otherwise the corrosion will continue unnoticed under the spatula. Also cleaning after sanding and before filling is extremely important. If the area to be filled is not really clean, the spatula may come off over time.

Step-by-step instructions for filling a body

  • primer
  • polyester putty
  • ink pen
  • Paint system (paint and topcoat)
  • Grease and silicone cleaner
  • Dust binding cloth
  • duct tape
  • cover
  • Thinning to clean the tools
  • Japanese spatula
  • Grinding tool (angle or orbital sander)
  • Sandpaper in different grain sizes (dry)
  • Wet sandpaper
  • possibly spray gun (if no spray can products)
  • sanding block
  • water bucket

1. preparations (grinding)

removing rust

First, the area to be filled must be completely de-rusted. Also, the paint in the immediate area is to be sanded. If necessary, the paint should be brought to the level of the sheet with fine water sandpaper. The rust really needs to be completely removed. If the corrosion reaches far into the metal sheet, it is advisable to remove it with the angle grinder.


Now the body surface needs to be accurately cleaned of silicone and grease. Spray on the cleaner, let it act and wipe it off with a dust-free cloth. Finally, blowing off the surface with an air gun would be a good idea if you have this tool.


Many fillers recommend to apply the spatula directly to the bare metal. We can not easily agree with that: putty products such as polyester putty draw water. Applying this putty knife to the unprotected sheet metal would soon cause corrosion again after filling and painting the bodywork. Therefore, it is recommended to prime the body shop floor to be trowelled after de-rusting and cleaning.

2. The filling of the body

Once the primer has fully set, you can start filling it. 2K polyester putty consists of putty and a hardener. The hardener is often heavily colored (pink or red). So that should not get the putty a certain color. Rather, you see so quickly whether you have stirred the hardener evenly with the putty. Approximately two percent hardener is used for 100 percent putty.

Now you can fill the body. Apply the mass on a large scale (of course in relation to the surface to be filled), following as much as possible the shape of the sheet. Do not apply too much putty in one go. A layer thickness should not exceed 2 mm, otherwise the risk of trapping air becomes too great.

After a few minutes (5 to 8 minutes), the hardener picks up. Now form small lumps, finish the processing of this spatula, otherwise you draw numerous grooves in the already troweled surface. Now repeat this process in another 1 to 3 steps. Always apply as little putty as possible. On the outside, the level of putty must definitely decrease.

3. The sanding of the filled body

Now you can start grinding. Conventionally applied polyester putty hardens enough at the right mixing ratio with the hardener after about 15 minutes, so you can grind it. Start with coarse sandpaper grain, which you refine more and more until you finally use wet sandpaper. On straight body surfaces, it is best to use a sanding block.

4. Filling the smoothed and ground body

Now you can apply the filler. There are products in the spray bottle and of course for mixing for the paint spray gun. Apply the filler thinly and allow it to cure completely.

5. Painting the filled bodywork

Now grind the filler again as smooth as possible with wet sanding paper. Finally, you can apply the color coat and then the clear topcoat.

Tips & Tricks

When you get to the point where the bare metal is visible, stop and continue filling.

You literally have to work with tact: any irregularity that you can "feel" with your fingers after filling and sanding the bodywork will definitely be visible after painting.

You can not apply 2K putties to a 1K primer.

Carrying parts of the bodywork must not be spatulated. These areas must be professionally welded.

Video Board: Porsche 911 Project Bodywork - Block Sanding Filler