Rough Sanding Partially Cured Filler

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Learning Old School NASCAR Bodywork: My First Time Using Bondo With Lessons From an "Old Timer"

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What happens here

Once the body filler has cured enough to be firm but still slightly sticky (usually a few minutes depending on temperature), use a 36-grit sanding block to knock down any high spots. This initial sanding is crucial because it's much easier to shape the filler before it fully hardens. Sanding the partially cured filler helps to blend the edges and remove major imperfections, preventing the need for more aggressive and tiring sanding later when the Bondo is rock-hard. Focus on feathering the edges to ensure a smooth transition with the surrounding metal, which is critical for proper adhesion and to prevent lifting or cracking.

Goal: Knock down high spots and feather edges of body filler.

Tools and materials

36-Grit Sanding Block — Rough sanding of partially cured body filler

What they say

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so now the stuff that I did first is not hard yet but it's cured enough that I can take this 36 grit and knock off the high spots before they get really hard and then they're harder to sand and then by the time I finish with this and I can do that area and that area and then by then the first area will be ready for the 180 grit to make it smooth anywhere to point now it is still kind of sticky but you cannot high spots that's really easy right now see that's about as far as I'm going to take it because once again I had a bad habit of doing too much with this and then I had to sand too much off to get the lines out and then it was too low so this is just for like like the high high spots big bumps like this and once this is all sanded I fully anticipate this area to be about half is what it looks like now but I'm gonna make sure I had enough on there that I could feather out to be smooth because what we're told is that

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