(quoted from post at 08:21:21 05/15/19)
I'm a painting novice, complete novice. I read this thread, because this is how I usually work... Rust Oleum... Krylon... cans are my friend.
Anyway, what I can't understand is this reasoning...
Chemical bonding is better than mechanical bonding, so do not scuff.
But, but, but... doesn't an increase in surface area facilitate better chemical reaction/bonding as well?
If you start with a dry substrate or coat and you're only scuffing just a little bit, so that you aren't going through the layer that you're scuffing, you're increasing surface area...which should help the chemical bonding, right?
Since I don't have years and years of experience, I read the instructions on the cans. Most of the cans nowadays have two sets of instructions for subsequent coats:
Usually, many of the newer finishes are tack dry in about 20 minutes, and they say to do subsequent coats within an hour, so that you're getting what I think of as a "wet bond"... no scuffing required. That's the first method.
But, then, the cans say that, if you have to wait longer to recoat, you then need to wait 48 hours for complete dryness, and then scuff a little before re-coating. That's the second method.
Guys like paintron, working in automotive and professional shops can optimize conditions, and recoating times. They can take advantage of the "wet bond"... us hacks...that have to work around work, animals, other commitments and such, usually have to scuff every once in a while; because we've had to let one coat dry past the wet bond state, while we're doing something else.