Removing primer without damaging paint

[HarmeetJohal1]

Hi all
I have a 1973 Audi 100 coupe S that was covered in primer in 1990 to protect its paintwork (don't know how that works?)
Anyway I would really like to see what's under the primer, all looks pretty solid, got the barn find running and roadworthy... Sadly I'm new to all this so need a little direction.
Was told to use 600 grit sandpaper and water (dipping and spraying it to keep paper clean and surface wet)
Had a little go today and it seems to be working, but will 600 be correct? Or will it damage the original paint? Is this the best way, read somewhere that maybe 800-1200 grit... Any advice or tips would be great. Don't want to burn or rub away the original paint if I can help it... Don't mind the patina look, but would love as much of it back as possible. Thanks

[227bhp]

It looks like it's a bit too late for advice, but I would have tested with paint thinners if the top primer coat could be dissolved and the bottom finish coat not.
I think you'll be saving up for a respray or driving around in a rat-look car.

[HarmeetJohal1]

have only done the roof...of I can save the rest would be great
What thinners would you recommend?

[paintman]

If the blue on the roof is the original colour & the grey patches with white edges are the original primer & undercoats under it then I'd suggest the reason it was covered in primer when you got it is that the previous owner had started to prepare it for a respray & then not proceeded for whatever reason.
If that is the case I would advise against trying to remove with thinners as you may well affect the original undercoats & good undamaged paint is often a good undercoat.

If you can't spray yourself your best course would be to speak to local bodyshops & see what sort of money they would want to respray & what - if any - work they would be OK with you doing.

[HarmeetJohal1]

paintman said:

If the blue on the roof is the original colour & the grey patches with white edges are the original primer & undercoats under it then I'd suggest the reason it was covered in primer when you got it is that the previous owner had started to prepare it for a respray & then not proceeded for whatever reason.
If that is the case I would advise against trying to remove with thinners as you may well affect the original undercoats & good undamaged paint is often a good undercoat.

Hi the blue is the original colour and the grey and white is the primer on top of the blue paint not underneath

[V8covin]

Try cellulose thinners but don't go mad.....or blame me if it goes pair shaped 😊

[finlo]

That looks more like you've broken though the clear coat!