How To Use Body Filler On A Car: A Step By Step Guide

Auto body repair shops have long been using body filler to repair bodywork damage and for auto restoration. The product is also excellent for small damage repairs. The purpose of this material is to fill-in low or damaged panel areas on a car in order for priming and painting. This material is available in different consistencies to meet a multitude of industry needs. In this article, we will be examining dent repairs and the proper process for using this product for small to medium size on a car panel surface.

In this article, we will be examining dent repairs and the proper process for using this product type for small to medium repair sizes on a car panel surface.

1) Using Body Filler – Assessing The Damage

The first stage of any repair is the initial assessment of the damage. A hammer and dolly can be used to re-shape the damaged area prior to using body filler if the damage is excessive. If the dent or repair area is small, then the next phase is the cleaning down of the repair zone. If using an oscillating sander, a heavy grade sandpaper can be used, 80-120 grade.

However, if not and sanding or surface cleaning by hand we would recommend using a lighter grain so as not to leave deep sand lines on the steel as these may show up at a later phase. Ideally, sand down the area with 180-220 grade sand paper and use red scotch pads to key the surface to give the filler product a surface to which it can grip (these are an abrasive pad available from all motor factor stores).

2) Choosing The Right Product

Once done with the initial cleaning phase and making sure that the surface is well keyed (this means that the surface is rough from the rubbing down, or sanding, process) before using body filler, as stated this creates a good area for the filler to grip. Now comes the first coat of fillers, and here is where industry knowledge becomes useful. The filler used is dependent on your requirements. For example, for larger repairs, it is best to use a high-build filler which is good at bulking such as ProWorx Elite or ProWorx Swift, either of which is ideal. If necessary, use Silk as a final skim coat for a perfect finish.


Apply ProWorx Pearl lightweight filler putty If the repair surface is large but shallow. All putties are ideal for finish coats due to their tight grain construction. For a very small repair or surface scratch damage which might only need one or two small skims we would recommend ProWorx Silk which is a glazing putty for finishing work. This takes very little sanding and which gives a perfect finish for the priming phase.

3) The Mixing Process 

After prepping the repair and choosing the right filler, the next step is mixing and product application. It is in this phase that many people start to make mistakes. When mixing the product be sure to mix it in a ratio of 100: 2 between the filler and the hardener. This is similar in scale to an orange (100 /filler) and a pea (2 /hardener). As you mix the hardener and filler be sure that the pink (colour of the hardener) is evenly mixed through the filler to change the consistency to an even shade throughout. Otherwise, it will not dry evenly.

4) The Application Of Body Filler

Be sure when using body filler to only mix as much as you need, over mixing often leads to over application of the product. This, in turn, leads to excessive time spent sanding down the product. It is extremely important to mix the product on a proper mixing surface and using plastic applicators. These mixing surfaces come as a solid plastic mixing board or as a board of treated paper. When properly mixed, apply in smooth, even coats. Smooth and shape using a plastic applicator.

Apply in layers, sanding between dry coats to eventually build a perfect repair.


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