My car currently has a couple coats of paint on it. One of the guys I work with told me that I need to strip it down to the metal, etch it, and then primer and block it. Otherwise, if I just scuff up the old paint with a sander I'll be blocking forever trying to get the waves out. He recommends using aircraft stripper in 3'x3' sections and going all the way down.

 

ok dude,if you strip it to bare metal get ready for a hell ride.While it would be nice to do it's unrealistic and WAY to time consuming.as long as the car is already straight it won't be difficult to scuff it then start blocking.you should be able to get it straight WITHOUT going down to bare metal,in fact it will probably be easier.The last car I worked on that was chemically stripped took a week and a half to sand thesurface rust out.Unless you can have the car dipped(not common and not cheap) I wouldn't strip it.

 

i stripped mine to bare metal if you only have 2 coats of paint on the car and it is all holding you may be ok just sanding and then 2k primer and the blocking all smooth. it really depends on you time..how long can car be down and how good of a result you want. if there is any lamination issue with the paint peeling bubbling ect strip it or you will continue to have those problems.

Jeff

 

Well I have between Thursday night and Monday morning to do all the prep before the paint goes on so I guess I'll just scuff up the old paint. What grit paper should I use to sand it down? Do I need to put a sealer over the old paint before priming?

 

no the whole point of scuffing up the old paint is to give the primer something to grab to, just scuff it up and send it in, i'd use a 60 grit to scuff it up

 

I'm painting it myself lol

Gotta learn sometime. I saw my paint after it got mixed at the store today, it looks fricking awesome, hope it comes out well.

 

60 grit! Way way too coarse for "scuffing" a car to repaint. Unless you like sanding scratches, I'd go no coarser than about 220. Once its in primer,guidecoat it with black laquer (I use 3m dry guidecoat) and block it in a crisscross pattern using a long sanding block (paint sticks work ok in a pinch). This will show you your low spots, and you can go back and build up those areas. I'd do the final sanding in 320 or 400. Some custom painters go finer than that (I usually do), but its not completely necessary.

 

i wet sanded with 400grit before shooting my base clear. this was after blocking with 220 and shooting more primer for wet sanding. i think if this is your first job you should give yourself more time to prep the car. rushing it will not give you the results you may want. painting is fast and is the easy part. prep is what counts for a good job. hell it should take a day to remove the gfx and mirrors and badges molding seals ect....

Jeff

 

No bout adout it.

 

Should I wet sand the primer and base coat or just the clear?

I'm kinda thinking I should go coarser than 220 to scuff up the original paint because there are currently two coats on there. I have a spare hood that I can try sanding to see what each grit does.

 

if you want to bust a level off use some 80 g on a d/a and work it down as even as you can. the put on a nice heavy coats or series of medium coats of 2k high build primer let dry and the block sand to get out inperfections and use a guide coat to help show the way. then shoot another medium coat and wet sand with the 400 that will give you a perfect base for you paint.

do not sand the base unless you mess it up run or something like that. if you do sand use the 400 and reshoot the area sanded. then 3 nice coats of clear and then after 24 hour cure wet sand 1000 or 1500 dependsing on how it looks. then buff it out with a power buffer. if you do not have a buffer do not wet sand you will not get it to shine hand polishing.

look up my project step by step on painting there is alot of info and pics that will help you. search on title " Project resurection"
2 would come up merged 1-3 and the rest merged.

Jeff

 

Jeff made a very important point. You can sand the primer to get the desired effect, but you must re-shoot the primer once done. The top layer of primer MUST be unsanded.

 

I have never heard that (not saying your wrong; I don't spray PPG so I don't know), but I routinely spray Spies-Hecker and some DuPont Chromapremier and always sand the primer. Is the unsanded top layer you are referring to a sealer? If so, I would agree, sealers aren't meant to be sanded.

 

actually sanding the primer down to 600 grit will give it a much much smoother surface than unsanded