The Difference between Body Filler and Putty


Today’s vehicles are thinner and have a more complicated body than those used in the past. As an auto body repairer, you may encounter small holes, door damage, hail damage, dents, and depressions.

You can repair these damages with body filler and putty.

What is the difference between putty and body filler?


Putty is a thick, transparent paint that contains a filler substance. It is used to fill in small cracks, scratches, holes, and other minor imperfections. It is usually used to fill small scratches in areas where the metal is not visible or before applying and drying the final paint. It is not used as a structural material.

Body Filler

A polyester resin called body filler can fill minor dents and smoothen curves for custom work. To make it work, you will need to add a hardener. Chemical hardening is when two parts hardener are added to the filler. The mixture is then called “chemical hardening.” Although it is an inexpensive substitute for body solder in many cases, it doesn’t last very long, and the main difference is that it is a structural material. Body repair shops have used putty and filler to repair body damage and auto restoration.

The scope of your project, the type of restoration, and preferences will determine the nature of the body-filler used in your restoration or repair project. Ensure to wash and dry your subject before adding filler or putty to it.

Fillers won’t stick to smooth surfaces, sanding the entire area without filling the rusty space. The filler can stain most subjects because the chemicals in the filler interact with the paint.

Reduce your chance of staining by following these steps:

  • Select a good-quality body filler
  • When painting, use a high-quality primer
  • Stop filling work when humidity is high
  • You should ensure that you have enough hardener
  • Mix the filler slowly and carefully
  • Do not trap air during handling
  • There are many types of body fillers

There Are Three Types Of Body Fillers:

1. Standard Body Fillers

The Standard grade body filler, which is lightweight, cures in 20-25 minutes. Galvanized steel should not be treated with this type of filler. However, it is excellent for minor scratches and dents.

After being primed and painted, they can be sanded easily and blended in with the rest of your vehicle. Standard grade body filler is also resistant to staining.

2. Medium Body Fillers

Because of its fiberglass nature, medium-grade fillers can be used on many body surfaces. It sands better than standard body fillers, adheres well to most surfaces, has a better resistance against staining, and can use it for minor repairs in your body shop. It can repair tiny cracks, holes, and tears in fiberglass or metal.

3. Premium Body Fillers

These premium body fillers are made of high-quality resin resistant to staining. Premium grade body filler is the easiest to sand and provides the best adhesion of the filler supplies to different underlying surfaces.

This type of body filler can be

used when you need to fill large areas or repair dents or when you need to make a lot of filler applications or sanding. Premium body fillers are quick to cure, flatten out quickly, and are easy to use. They are powdery and unlikely to block the sandpaper, allowing it to flatten the sides of your car and straighten the body lines. Premium body fillers such as these are the best because they have been designed to sand quickly and last long.

Tip1: While you can use the standard body filler to fix minor hail damage and small areas of rust, the premium body fillers are best suited for larger rooms or tears.

You will get the best results if you pay attention to the instructions and combine the correct amounts of crème hardener with filler.

Tip2: Too much hardener mixed with too little filler can cause the filler to become stiff and crack.  You can delay the drying and hardening process if too much hardener is added. It is not difficult to do it correctly.

Non-cardboard mixing boards are best because they have no leaky properties. Remember that cardboard can affect the harmony of your filler.

Tip3: Filler projects should be completed on a dry, warm day to allow the filler to cure more quickly.

Do not use the filler on rusty areas. If you have rusty regions, it is essential to remove them first. Otherwise, the filler will not adhere well and cause discoloration or staining to your project. Filler sticks well to smooth surfaces, so sand any areas that need improvement.

Tip4: To get the best results, you must roughen the surface. Always wear a dust mask when using filler to avoid the adverse implications of its chemical makeup.

Sometimes your filler may feel hardened too quickly during the application, and you can avoid this by using a thinner filler (sometimes called “Honey”) alongside you.

What is Putty?

On the other hand, putty is a high-plasticity material similar to clay and dough. It is used as a filler and sealant in domestic repairs and construction. Putty is a linseed oil-based product that can fill holes and minor cracks and repair or replace damaged items.

It is excellent for repairs or dents that are small and quick. It cures once you have it applied to a smooth surface. You can sand putty with fine-grade sandpaper, allowing the surface to be smoothened for painting or primer.

Putty is made from fine grain talc, which gives it a tight grain finish, making it one of the most popular finishing fillers. Today, body restoration products are easy to sand, which allows for better results and less effort.

Two-part polyester putties are popular in Auto Body shops for filling minor car dents and other body imperfections. Putty can create a flat finish on top of thicker layers.

Body putties, often two-part polyester inventions, are similar to body fillers. The polyester base is mixed with a hardener, which cures quickly and allows you to sand the surface in 15-30 minutes, depending on the air temperature and the amount of hardener.

Tip 1: Avoid mixing the hardener with the filler to avoid pinholes. It would be best to fold the hardener in the stuffing and squeeze out any air pockets.

Good quality putty will stick very well to your surface and mildly shrink as it cures. It will also sand easily with a thin, feathered edge.

You can use putty to fix minor imperfections like pinholes and sand scratches. Both will dry quickly.

Tip 2: Allow the putty filler product to cure before starting the sanding phase entirely. If the product doesn’t ‘powder” after application, please be patient and allow it to heal.

The Bottom Line

Your choice of body filler as an auto engineer should be based on the job, your discretion, and your ability to complete the repair quickly.

Although any type of body filler is acceptable for repair, it’s essential to distinguish between body filler and putty. Remember that professional finishes require products suited to the stage of repair you are in or the extent of the damage.


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