Start with 100

When block sanding polyester primer, 100 grit on True Blox is the perfect way to start sanding. Why?

  • Polyester is a hard surface to sand, usually with a heavier texture than other primers. 
  • That hard surface requires a sharp sandpaper to get it leveled flat. 
  • Anything finer than 100 grit follows the texture too much, and doesn’t cut it flat enough, leaving it with a slight ripple, rather than truly flat.  Smooth is not the same as flat. 
  • The hard surface of True Blox doesn’t allow the sandpaper to follow the texture of the primer, allowing the sandpaper to cut the texture flat. 
  • 80 grit also cuts polyester flat, but it leaves a deeper scratch, creating additional sanding steps. 

Don’t be fooled by polyester. Of course it’s possible to sand it with finer sandpaper, and it will appear to be working the same. The subtle difference really starts to show up when you’re wet sanding the paint, and just can’t get it quite as flat as you’d wish. That slight ripple might be partially from the polyester not being blocked hard enough. 

If your goal is to do the best body work and paint possible, it’s all about some of the smallest details. This is one of those important details that makes a big difference. 


1 comment

  • After blocking the panel flat- 100 grit on polyester, what is your follow up step. More polyester blocked with finer paper or build primer.

    Dave Boyd

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