14 replies to this topic

[finch661]

hey all, just a quick question. I am planning on repraying my car, as i am replacing  a few panels. the majority of the paint work is ok with a few rust spots. i am planning on keeping the same colour. What grade of sandpaper should i use to key the surface for painting (the good paint work anyway)

 

thanks

 

Rich

[Morry Stu]

600 wet & dry for your old paint.

What paint are you using and do you know what the original paint is..This is important as different paint types react with each other.

[finch661]

the old paint is 2k (2 pack?) the nasty stuff any way. will be painting with celly! will i need to put primer coat on because of the old paintwork?

[Morry Stu]

http://www.rodsnsods...int-28625/page2

[finch661]

cheers for the link. so it  looks like i need to be careful then with painting over 2k.

 

so what would be the best plan of attack

[Daz1968]

I wouldn't worry about it, once 2k has cured it won't be softened by cellulose thinners. Hardest problem will be flatting it as it's much harder than primer to flat. If paint on car is original I would dry flat it with p400 then put a coat of high build on and flat that with aid of a guide coat and block. I used p500 dry at this stage but I was using 2k gloss which doesn't sink like cellulose so maybe p800 wet for cellulose,

[Morry Stu]

Your patches in the 2k will show if you dont fill and sand. You may need to do this 3-4 times to build it up.

[Ben_O]

Any paint that is completely sound i.e no blemishes, rust or deep scratches will require no more than a going over with a scotchbrite pad and some prep and blend paste.

 

It is always good practice to make sure the bodywork is one uniform colour before painting as it reduces the chances of odd panels and dark/light patches so if you have quite a few repairs to do, might pay to give it a go over with some primer first

[finch661]

i will sand down using p300 and spray with some high build primer on it as well. there will be filler here and there, so better make sure. thanks

[Morry Stu]

300 will leave deep scratches.

[Ben_O]

It certainly will. High build primer is meant for building up a decent level of material so that very minor imperfections can be evened out.

 

300 grit paper will take down scratches and the like quickly but then leave you with more work. Prep work is 99.9% of the finished job and shouldn't be rushed. Its just one of those things that if you hurry or cut a corner, you will never be happy with the result.

 

800 grit is the only appropriate grade to use really and is what would be used in a paint shop for flatting primer etc so best to stick with that mate.

 

Ben

[finch661]

ah cool, cheers for the info. luckily i havent started this project.

 

so 800 grit to key the old paintwork, then build primer, then flat again, then paint?

[Daz1968]

^{Also please remember that grades quoted wet and dry are not the same. P800 wet is about same as P400 dry, I use abranet dry and P600 is finest they do I think, my common grades for various stages is P120, P240, P320, P400 and P500.} 

[Morry Stu]

Yes. perp is 99% pf a paint job.

600 is a good start to key in a primer onto old work. 800 is better as it leaves finer scratches,but some surfaces need a slightly courser finish.

As you build your primer you should go up in grade with every coat.

Start at 600,prime,cut with 800,prime then guide coat with flat black,cut with 1000.

You need to cut back with finer grade down to the level of your previous grade.

The finer the cut, the longer it takes.

Once you put your first colour coat on, cut it with 1200, then cut each coat with 1200+

If your using celly/acrylic on a solid colour then on your last coats add some clear to the colour. Gives the finish a beautiful glass look.

[Morry Stu]

My old ute was painted 15yrs ago with acrylic+ clear on the final coats.

Has held up well and has a nice glass look to it

http://www.theminifo...ttach_id=160330