I sprayed duplicolor primer + auto paint on the body. I want to use some other kind of primer. Do I need to strip the guitar before using the primer? Or can I just spray primer on top of duplicolor paint?
Although i don't know for sure, my initial thought is that it probably isn't a good idea to spray a primer on top of paint. I guess it depends on how good a job you did originally. If its all bumpy and messy, then i would definitely say strip it back and start again. But if you've done a stella job already, then id be tempted to say go ahead with it.

However, i must point out that i know absolutely nothing about painting guitars professionally - im merely using my common sense (which probably isn't wise to do so). So wait until someone with experience comes around.
I are chav.
You need to at least flatten the shine off it - no need to sand it back to bare wood though!
600 grit wet sand in between all coats is what i reccomend. VERY lgihtly though.remember to tack cloth when dry.
Quote by Invader Jim
The questions people ask here makes me wonder how the TS's dress themselves in the morning and can shower without drowning...
I am from the UK, so over here we have a different P grade of sand paper, with lower numbers.

If you look HERE you can see a chart which compares the CAMI grade commonly found in the USA/Canada and the FEPA P grade, more common in Europe.

CAMI grade is less stringent on particle size, than the P grade, so 600 may contain larger as well as smaller grit sizes.

As you can see, your CAMI 600 grit, compares to our P1200, which is for starting to finish lacquer with!

P600 is way to fine for a sand between primer and basecoat. You need around P320 grit to help get a good bond at the max really.

You only want about P220 on the actual substrate (wood), before the Primer goes on.

If you use a very fine paper on the substrate (wood) or Primer, you will not create an effective bond between the two and your paint job will suffer, perhaps peeling off in great lumps.

You don't sand colour coats (if you are using a base and lacquer system), only in very rare circumstances. You cant sand a metallic, or pearl finish etc, coz then it wont sparkle!

You need to spray an intercoat "clear" over the colour, then sand that. But only if you want to add different colours, artwork, masking or pinstriping etc.

The reason you don't need to sand the basecoat/colour coat, is because the lacquer you apply, will fill all the bumps and valleys in the basecoat. Or if it's another coat the same colour, then that coat will fill the bumps and valleys (yes it will leave behind more)

Then you can sand the lacquer with P500 wet or P600 dry, apply 1 or two wet coats of lacquer and then you can set to wet sanding to P2000 grit.
This will give you your flat surface then buff and wax it to bring out the deep mirror shine.

I hope that helps.

To answer your question. Any paint job, is only as good as the layers beneath it.

If you badly prepare your substrate, every coat after that is at risk.
If you do a crap job on the Primer, the basecoat and lacquer are at risk.

So. If you applied the primer to bare wood, properly prepared (see above), free of impurities etc and did the same with the colour coat, Then all you need do, is sand the surface to about P220, then re-prime and so on.

If you have any doubts about the quality of the paint job on there, strip the lot off.
Preferably, sand it off, but of you must use a chemical stripper, make sure you use plenty of water etc to neutralise it and allow time for it to dry properly etc.

Buy some MILD panel wipe from what you would call an Autobody store, and use this to wipe down the wood, and wipe off again with a clean cloth afterwards, wear plastic gloves, so you don't leave crap and oil from your skin on the surface.

As was stated, tack cloths are great too.

Do the same after sanding inter coats, or lacquer. With lacquer, you can just use water if you wish.

Whatever you choose to paint with, use one system. Don't use one system for the primer and another for the basecoat and another for the lacquer, as they will not be designed to work together.

I only use House of Kolor, for no other reason than that is what I started using initially, I have a feel for it and it works. It is also reputed to be the best in the world and I certainly would have no doubt in believing that to be the case.

Many people will turn around and say that they can achieve a "great" finish by just spraying paint on willy nilly and not following any particular procedure and that may work for them, but a truly GREAT paint job, only comes from doing it right.

I have had people pay me for work that I have done, sometimes quite a bit of cash.
I cant afford for someone to turn up two years later, because the paint is lifting, or cracking.
Or even sooner. I had a guy who had had a guitar sprayed up by someone, polished, looked great and it only took him a week.
This owner was pretty pissed, when 4 weeks down the line, ripples were forming in his now much duller looking finish.

I had to fix it. The first "pro", had used regular lacquer, rather than a two part Enamel. Which is fine, if you let it set up for 6 weeks before cutting it and polishing it.

He didn't. So as the lacquer shrank back as it set up, ripples appeared and the whole thing looked crap.

He paid £400 for that paint job and it lasted a month.

The catalysed primers and lacquers I use, dry rock solid in 24 hours at 30 degrees C and can be cut (sanded) and polished after that, with no ill effects.

Please excuse the essay and preaching!
Last edited by Skeet UK at Sep 5, 2008,
I'd hit it with 400 grit on a flat sanding block til its flat with no shine, then start spraying the primer.
All my photobucket pics are dead so no links to my guitar build threads.
My Music