Selecting the right body filler for your automotive project can be more difficult than it seems. There are countless filler options, each tailored to unique types of damage repair and finish requirements. Figuring out which filler will best meet your needs can feel like a guessing game. Choosing the wrong one can lead to subpar repairs, wasted materials, and worse – the need to start over.
Whether you’re repairing small dents or addressing larger structural damage, understanding the different types of fillers can make all the difference in your project’s success. From conventional polyester fillers to fiberglass-reinforced options, here’s an overview of what to use for what job.
Polyester Filler
The old standby, polyester body filler (like Eastwood Contour premium body filler) is ideal for leveling small to medium-sized dents and imperfections. It works on a variety of surfaces including metal and fiberglass to create a smooth surface before priming and painting. With enough time and patience, this is a good all-arounder.
On the upside, it’s generally easy to mix and apply, even for beginners. It also sands well and smooths out easily after curing. And it’s generally the most affordable and widely available of the fillers.
However, you’ll need to account for some shrinkage as it cures, which might cause surface imperfections. Pinholes are common and it can absorb moisture if not sealed properly, leading to future rust or paint issues. Of all the fillers, it’s more prone to cracking over time, especially if applied too heavily.
Lightweight Polyester Filler
Like its name implies, lightweight filler is typically used for smaller dents and imperfections. Ease of sanding is considerably better that regular polyester filler thanks to its lighter build. It’s ideal as a final coat over conventional fillers to achieve a smooth surface.
Premium lightweight filler has a lot going for it. It tends to be easier to work with and provides a finer finish with less sanding required. Plus it sands more easily, allowing for quicker refinishing. Shrinkage is also less than with conventional fillers, reducing the risk of post-application issues.
However, you can expect to pay a little more for these advantages. It’s also not as strong or durable as reinforced fillers, making it less suitable for high-stress areas.
Fiberglass Reinforced Polyester Filler
When you need structural strength and corrosion resistance, call in the big guy. Reinforced with fiberglass, this filler is often employed to fill larger dents and holes. It’s also well suited to rust-prone areas and fiberglass panel repairs, naturally.
The main advantage here is the inclusion of fiberglass strands, which make it much stronger and more durable than regular fillers. This allows it to be used in high-stress areas where regular fillers might fail. Perhaps unexpectedly, the glass fibers also help reduce the occurrence of pinholes, making it excellent for rust-prone areas such as wheel wells and lower panels.
Adhesion is superior as well, bonding tightly to various surfaces, including steel, aluminum, and fiberglass.
Reinforced filler is notably more difficult to sand due to the glass strand, requiring more effort and time. Lightweight short-strand filler, however, has become easier to work with recently. Glass inclusion make it heavier than lightweight fillers, which may not be ideal for all applications. And of course, it’s more expensive than standard polyester fillers.
Finishing Glaze
Finishing glaze is generally used as a final skim coat to perfect the surface before priming and painting. It’s ideal for fixing small pinholes, sanding scratches, and surface blemishes after initial filling.
Its thin, lightweight consistency provides an exceptionally smooth finish, allowing for a flawless final surface prep. It cures quickly, allowing for faster turnaround, and it has very low shrinkage, reducing the likelihood of surface imperfections.
Of course, finishing glaze has its limitations, notably its unsuitability for filling large dents or deep imperfections. It requires thin applications, so it’s not ideal for filling deeper flaws, either. Depending on the brand, it can be more expensive than conventional fillers.
Whether you’re fixing minor surface imperfections or tackling more significant damage, selecting the appropriate filler can mean the difference between a seamless finish and a frustrating redo. Understanding the strengths and limitations of each filler will help you choose the best one for your project, ensuring a repair that is both smooth and long-lasting.
@Douglas – If you can get down to clean metal, you could apply the fiberglass-reinforced filler directly to the metal. Otherwise, Rust Encapsulator will seal any remains rust and you can apply the fiberglass-reinforced filler to maximize the adhesion and minimize moisture intrusion in the filled area.
I am renovating my 1999 S10 extended cab pickup. I discovered an area in the driver’s foot well area where the floor is rusted through.
Is this a situation where I can apply your encapsulator product then repair the floor with your Fiberglass Reinforced Polyester Filler ? Any advice will be appreciated.