What grade of wet&dry

[whiskeyfrank]

Ive got a classic car and its got a thin cellulose top coat which has been sprayed on primer which in turn looks like its been sanded with 80 grade.

Its full of scratches under the paint and dents so ive rubbed it down with 240 to get an even finish, but what grade should I use before applying a primer coat?

[OldskoolRS]

I'd work up to 600 and maybe 800 grade, but it also depends on what kind of primer you're going to use. I used to prime with 'high build' cellulose primer so 800 grade seemed fine enough. Modern paints may be different, but seeing as no one else has responded so far...

Also, when you've done the primer coat(s), spray a 'guide' coat on with a darker colour and wet flat the primer again. The guide coat will help you to spot any imperfections before you waste the top coat and it will help you to make sure you've flatted the entire area and not missed any areas. You may then need to do some 'local' touch ins with the primer, and reflat, but that's better than seeing a shiny topcoat spoilt with a rough area under the primer.

[whiskeyfrank]

thanks for the reply, im using high build so ill try 800 and see where i get to

[SAL73R]

You will cover P320 scratches with a wet on wet primer and more and you are just causing your self more work. You can go any where upto P1000 though if you really like.

[steveo3002]

id go with 600 or 800 , go too fine and its not enough of a key

[OldskoolRS]

Originally Posted by SAL73R

You will cover P320 scratches with a wet on wet primer and more and you are just causing your self more work. You can go any where upto P1000 though if you really like.

In hindsight, this may be closer than my suggestion as it's been a long time since I've done any spraying. Maybe a little finer than P320, but perhaps not as fine as P800. I'd definately use P800 to flat the primer before top coating though otherwise you might see sanding scratches under the top coat which you can't polish out.

[SAL73R]

Originally Posted by OldskoolRS

In hindsight, this may be closer than my suggestion as it's been a long time since I've done any spraying. Maybe a little finer than P320, but perhaps not as fine as P800. I'd definately use P800 to flat the primer before top coating though otherwise you might see sanding scratches under the top coat which you can't polish out.

That is correct I do it every day for a living. Primer WILL cover 320 scratches no need for the 800 flatting process. The highest I ever use is 500 for taking high build primer down every now and then.

[OldskoolRS]

Yeah, like my screen name I'm 'oldschool' and did a fair bit of DIY spraying maybe 15 years ago, mostly cellulose. Aprreciate the Pro tips. Done the odd small repair with cans in recent years, but planing to dig out the old Devilbis at some point again soon, but times change and things move on...hope I'm still up to it. Getting the MIG out later this week, so we'll see if I'm still upto that first.

[squiggs]

Surely it all depends on which primer you're using and what the manufacturer of that primer recommends.