Automotive Body Filler: The Essential Guide to Perfect Vehicle Bodywork

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When it comes to automotive bodywork, achieving that flawless finish is both an art and a science. This is where body filler becomes an indispensable tool in the resource of the professionals. In this comprehensive guide, we examine the world of automotive body fillers, focusing particularly on the innovative solutions provided by ProXL – namely, the ProXL Deep, Medium, and Fiberglass fillers.

The Need for Body Filler

Every vehicle, over time, encounters its fair share of dents, scratches, and imperfections. Whether it’s due to accidents, environmental factors, or the natural ageing process, these flaws can mar the beauty and integrity of the vehicle’s exterior. Body filler, a substance capable of filling and repairing these defects, is crucial in the restoration process. It helps in achieving a surface that’s not only aesthetically pleasing but also structurally sound.

Understanding Imperfections

Before delving into the specifics of body fillers, it’s essential to understand the types of imperfections commonly encountered:

  • Dents and Dings: Often caused by minor collisions or impacts.
  • Scratches and Scuffs: Resulting from abrasive contact with objects or surfaces.
  • Rust and Corrosion: Occurs over time, especially in vehicles exposed to harsh environments.
Dents Dings

Problems Faced in Vehicle Body Repair

Addressing vehicle body imperfections isn’t without its challenges. Common issues include:

  • Shrinkage: Some fillers may shrink as they dry, leading to an uneven surface.
  • Adhesion Problems: Ineffective bonding with the metal surface can lead to filler detachment.
  • Over-Sanding: Excessive sanding can damage the surrounding area and lead to more work.
  • Colour Mismatch: Ensuring the filler blends seamlessly with the original paintwork can be difficult.

ProXL Fillers: The Solution to Bodywork Challenges

Westco is pleased to be a trusted stockist and distributor of the ProXL brand of filler products. ProXL has developed a range of fillers designed to tackle these challenges head-on. Let’s explore the unique properties and benefits of each type:

Ultra Fill Medium

ProXL Deep Filler

  • Formulation: Ideal for moderate imperfections, providing a balance between filling capacity and ease of application.
  • Benefits: It offers excellent sanding properties and a fine finish, making it a versatile choice for various repair needs.
Ultra Fill Deep

ProXL Medium Filler

  • Formulation: Specially designed for deep dents and significant damage.
  • Benefits: High adhesion properties and minimal shrinkage, ensuring a smooth finish even in deeper repairs.
Ultra Fill Glass Fiber

ProXL Fibreglass Filler

  • Formulation: Reinforced with fibreglass, perfect for repairing larger, more structurally compromised areas.
  • Benefits: Provides exceptional strength and durability, essential for areas requiring robust repair work.
Untitled design

ProXL Ultra Fill Glaze

  • Formulation: Crafted for fine surface imperfections, this glaze combines a high level of filling with easy, smooth application.
  • Benefits: It ensures a superbly smooth finish with minimal pinholing, ideal for achieving a flawless surface before painting.

The Filler Application Process: Tips and Best Practices

Applying body filler requires precision and care. Here’s a step-by-step guide to ensure optimal results:

  1. Surface Preparation: Clean and sand the area to be repaired, ensuring it’s free from rust, dust, and grease.
  2. Mixing the Filler: Follow the manufacturer’s instructions of 2% hardener for correct mixing ratios to achieve the right consistency and avoid bleed through.
  3. Application: Apply the filler using a spreader, ensuring even distribution over the imperfection.
  4. Curing Time: Allow the filler to cure as per the recommended time, avoiding quick fixes.
  5. Sanding: Once cured, sand the area smoothly, starting with coarser grits and moving to finer ones for a perfect finish.
  6. Finishing Touches: Clean the area and apply primer, followed by paint, to match the vehicle’s original colour.
Body Filler Mix Ratio


Achieving a flawless finish in automotive bodywork is a meticulous process that requires the right materials and techniques. ProXL’s range of body fillers – Deep, Medium, and Fiberglass – offer tailored solutions to various repair needs, ensuring that your vehicle not only looks good but also maintains its structural integrity. Whether you’re a DIY enthusiast or a professional, these fillers can help you overcome common bodywork challenges and achieve perfection in your automotive