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painting problems - help anyone?
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Author:  J_A_M [ Mon Mar 22, 2004 9:44 am ]
Post subject:  painting problems - help anyone?
I was spraying my bonnet on the weekend. The original paint was in OK condition, just very thin. I sanded it with an orbital, then some 400 wet/dry. In some places it was bare metal and others it was still the original blue colour.

I decided not to hit this panel with etch primer, and use Hi Fill Primer as the first primer. It seems that there is a reaction where the original blue broke through to bare metal, and the primer is crazing in these places.

Questions:

1. Would the etch primer have gone on without any reaction?

2. What could be causing the reaction? I cleaned the surface with Prepsol, so it can't be oil or wax or whatever.

Cheers,

Anton.
Author:  850_Van [ Mon Mar 22, 2004 9:51 am ]
Post subject: 
if its bare metal in places, you should etch prime them and then hi fill with primer, then sand it back with 600 to make it all smooth ready for the next coat
Author:  marconi [ Mon Mar 22, 2004 9:52 am ]
Post subject:  painting probs
Its likely that the bonet was painted in some enamel based paint at some stage. Laquer based thinners reacts with these finnishes. You can A use an isolater or B sand it right back to metal all over. IMHO be very carfull with orbital sanders you don't want to dig your self a hole you will need to fill & allways use a sanding block with wet & dry.
Author:  J_A_M [ Mon Mar 22, 2004 10:06 am ]
Post subject:  Re: painting probs
marconi wrote:
allways use a sanding block with wet & dry.


Do you mean a cork block? I have always wondered what people refer to when they say 'block' it back.
Author:  marconi [ Mon Mar 22, 2004 10:16 am ]
Post subject:  sanding
It could be cork or Rubber. I have been tryling some foam packing that I cut into blocks with a hack saw. as long as its flat firm & slightly flexable & you can wrap wet & dry round it and holdit in the palm of your hand.
Author:  Big Dan [ Mon Mar 22, 2004 11:00 am ]
Post subject:  Paint
"It seems that there is a reaction where the original blue broke through to bare metal, and the primer is crazing in these places" :(

Anton I have heard of this happening before on early clubbies (like 1972 - 1973) and it is for this reason that I decided to go with sand blasting and starting again from bare metal. Apparently it has something to do with the paint used on the early Clubmans, but I thought they had changed this by 1976... maybe the bonnet has been replaced by one off an earlier vehicle at some stage??? Anyways, the best way to fix the problem is to sand it all back to bare metal or to use an isolater like marconi has said already... I prefer the bare-metal approach myself, but either works.

Big Dan
Author:  J_A_M [ Tue Mar 23, 2004 7:33 am ]
Post subject: 
Thanks fot the tips guys.

I stripped off all the paint from the bonet last night (right to bare metal), including that which I had just sprayed the previous day.

I etch primed the bare metal, then hit that with Hi Fill Primer and blocked it back (with 280 wet/dry and a cork block) and the finish was EXCELLENT!

Someone once told me that a great paint job is 90% prep and 10% application. I had been sticking to this theory for most of the car (stripping the body and other panels to bare metal) but I just got lazy with the bonet and paid the price.

Anton.
Author:  J_A_M [ Thu Mar 25, 2004 8:50 pm ]
Post subject:  Re: painting probs
marconi wrote:
Its likely that the bonet was painted in some enamel based paint at some stage. Laquer based thinners reacts with these finnishes. You can A use an isolater or B .........


Excellent tip - THANK YOU. I sprayed the problem areas with an isolator and then primer over that - perfect!!

I didn't know about Isolators, so thanks for the tip.

Anton.
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