What Causes Paint Crackle and How To Fix This: Auto Body Q&A 😰

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It’s Tony from LearnAutoBodyAndPaint with another session of auto body Q&A. Today’s highlight is What Causes Paint Crackle and How To Fix This. 

Question: Any tricks for prepping a fibreglass body for paint?

It’s the same exact process when doing regular bodywork. You’re going to lay 2K filler primer and not epoxy primer on top of it. You can finish sanding with 120 to 220-grit then lay your 2K filler primer on top of that, followed by glaze putty if needed. Lastly, cut it down and get it ready for paint.

Question: Why dry and wet sanding with 400-grit?

In my opinion, you’ll get a cleaner cut when doing final wet sanding while washing all the dust off of the car. You don’t have to do wet sanding and just stick with dry sanding. However, you’ll be risking areas of having cake powder that wasn’t washed off. I prefer initially doing dry sanding with 400-grit then wash it down again with 400-grit wet sand. 

Question: Can one add clear coat with a silver flake on top of single-stage paint?

Yes, you can. I recommend sanding it with 800-grit prior to doing this process. Then, mix up your clear coat with mini flake in it, and put two coats of clear. You can put one coat of clear coat on it without the mini flake or finish it off with two coats of clear with the flake. However, it depends on what flake. You’ll be fine if you’re using a micro sequence or mini flake. It won’t pop out of your clear as much as your jumbo flake. 

Also with the jumbo flake, it will come out very rough, which is why you’ll need to cut it down with 800-grit on a DA sander to flatten it out. Then, put two more coats of clear coat on top to bury it. Lastly, you need to sand that, get it flat and buff it out. 

Question: What causes paint crackle when you lay down your base coat and how do you deal with it?

You’re probably referring to paint biting or when you lay your paint on, it looks like a map, another word for it is mapping. 

It can mean that you lay your coat too heavy. Another reason for it is a chemical reaction wherein some oil or silicone-based product was put on the panel. Hence, you need to make sure to use wax and grease remover all the time before painting. You need to wipe everything down with wax and grease remover and tack it. Always put a light coat on your panel to make sure everything is laying down well. If you put on a light coat, you’ll be able to see the chemical reaction 

If you see something like that, keep going with the light coats and let it dry in between. However, if you are at a point where you see some mapping, you’ll need to let it dry. If you’re doing base coat, you’ll need to let it dry really hard for about an hour and then block it out with 400-grit. Then, wet sand it with 400-grit and take it off. Get it smooth again and just repaint it. 

You should be okay if you’re painting over a 2K primed surface. If you’re encountering the same problem, it might be your surface, you’ll need to use a sealer or a filler primer. You need to reseal or prime it, let it dry, wash it down and cut it down with 400 to 500-grit then lay your paint on it. 

Question: After sanding clear coat off, do I wash the car before priming car?

You don’t have to wash it with soap. You can just wash it down, but you can use dish soap or any kind of car wash that doesn’t have wax in it. 

I prefer using dish soap that can take the grease off, but don’t use too much dish soap or else it will get too bubbly. You just need a squeeze of the soap in a 5-gallon bucket. 

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Thanks everyone for joining today’s session highlighting the question, “What Causes Paint Crackle and How To Fix This”. Please hit that 👍 button, share and subscribe to my channel! Click on the 🔔 icon to turn notifications on so you’ll get notified of new videos. 

Talk soon guys! Cheers! 


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