Ok, there’s a few things to answer hear so I’ll do my best to answer with the caveat that I’m not an expert of course
. So here is my understanding which I’m happy to be corrected on if needed.
A chemical bond is when paints melt together to a degree in order to stick and create adhesion.
A mechanical bond relies more on the texture to stick.
If we start with the base coat. - for best adhesion solvent base coats have a “clear window”. They rely more an a chemical bond meaning after being sprayed they must be cleared within a certain time period and wouldn’t need sanding to accept the clear coat. If it’s not possible to clear within this period then they will need to be sanded to create more of a mechanical bond.
Water based paint does not have a clear window as it is more of a mechanical bond. You can leave waterbased for a week or more and then clear it without needing to sand.
Base coats that are not metallic or pearls can be sanded to correct imperfections before being cleared.
For the common clear coats - Rattle cans are generally a 1k product meaning they don’t have a separate chemical (an activator) in order to dry. Clear going into guns is generally a 2k product meaning it does have a separate activator that must be added to the mix in order for it to dry.
Both of these are of course solvent paints and will sort of melt into previous coats.
When applying either 1k or 2k clears you don’t specifically need to sand in between coats. Often the TDS will say to spray another coat while the previous one is still tacky and not dry in order to achieve that chemical bond. If you have any big problems such as dirt or a bug you can let the coat dry, sand out the problem and then put following coats on top. Although the previous coat has dried, because you have sanded you now have a mechanical bond and you’re off and rolling again.
With both 1k and 2k I have learned I’m generally better off ignoring most dirt that lands in any coat and carry on. Because I finish them with a lot of sanding and polish, pretty much all of the dust disappears.
There’s obviously a lot to the application to achieve a perfect clear coat (something I’m still learning to try and achieve)! But I have learned that it is more forgiving than you think.
The only time I have had any problem that I can’t correct is by putting too much clear coat down too quickly and have it wrinkle or bleed to paint below.
Feel free to message me if this post is confusing! Lol. There’s some very good videos on YouTube that explain things pretty well.
As I said, this is my understanding which may be flawed. But hopefully some of it is helpful at least.
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