Morris Minor Owners Club

Hi all, just put some primer on some of my panels at the weekend, this morning i went and had a look and there is loads of cracks in the primer!, i need some good advice on what may cause this, i am thinking the consistency of the paint, the supplier i bought it from said its 50/50, i am tempted to try possibly 75/25 or something similar and see what happens, i am painting in cellulose and bought primers to go with it, also i had no problems with my zinc primer coat and i made this 75/25, any advice would be appreciated.
Also i bare metaled the panels, degreased etc, i painted my last car in 2k and had no problems at all, clearly i can't be putting top coat on this if its all going to crack.

Any ideas???
cheers

Too thick a layer ? Reaction wit the thinners?

i think too thick could be the one, in fact i am almost sure, i just read a few old threads, and i think i may have put to much on too soon, i will try a nice thin one on another panel and see what happens.
cheers

Many thin coats is the way.

too thick a coat and not enough time between coats the top coat flashes off before the one underneath has dried and the cracks develop,you will need to take it off to a sound base or it will allways be a problem,you may be able to sand it off back to the zinc primer.

Did you take the panels down to bare metal?? If so then you will need an etch primer coat before the cellulose filler primer coats.

Also, did you use a paint stripper?? All paint stripper needs to be carefully removed before applying any top coats.

I think for sure i have put to much paint on too soon, its the only logical explanation, i have already started flattening the panels, getting as much of as possible, what a nightmare thank god it was only the wings front and rear and not the whole car, really i should strip the paint completley off, but i have already done this so i am going to get as much of as possible with wet and dry and give them another coat and take my chances, do you think there is a good chance i could keep getting cracks in the future if i do this? clearly you just don't know but to be on the safe side i should get as much of as possible.
Its not a reaction from the paint stripper as i cleaned them thoroughly and had no problems with the zinc primer and also some bits are fine and others mainly with curves i.e front bumper, front panel have cracked the worse.
thanks for your tips i appreciate it, i should have done a bodywork apprenticeship not mechanics! perhaps i would have learnt to be more patient!!!!

Even in warm weather you should apply just one coat of primer (half overlapping passes with th spray gun) and leave at least 15 mins for the primer to flash off before applying the next coat of primer. Then leave a few hours or preferably overnight before flatting and top coat.

Try to keep the gun parallel to the surface - and maintain the same distance as you pass over the panel - not going closer at curves etc. Also important to 'trigger' the gun just before the start of each pass - and release just after the end. Don't wave the gun about like a conductor's baton...............

[quote]mainly with curves i.e front bumper, front panel have cracked the worse. [quote] well there the clue,You must keep the gun at the same distance from the surface as you go round a curved panel your hand should draw away as the peaks are reached,and draw closer as the concave bits are reached,otherwise you get too much paint on the peaks and dry rough bits on the concaves,just takes a bit of practice you'll get there soon enough good luck

thanks mate, thats good advice, i had no problems with my last paint job, but it was 2k i am not sure if that makes a difference?, anyway i have flattened them and am going to zinc prime them again tomorrow.
my other zinc primed panels,shell and these panels are fine so i basically cocked up the primer.
Just a quick one how long do you think i should give the zinc primer to set before i put the normal primer on? week i thought should be plenty but i would like to be definate, also i may do one of the rear panels and see how that goes before i put any on the shell, i do not want to have to be rubbing everything down again!, i will just have to learn to be a bit more patient!
thanks all.

After it's dry - stand it out in the sun for a day.

I normally leave primer overnight before applying top coat,as an asside there has been a lot of talk on the scimitar forum about wet flatting primer,and the pros who are doing rebuilds have all stopped wet flatting and only use dry with cotton gloves to prevent moisture contamination,apparently they are finding that even after you think the primer has dried out if you have used water then there is a good chance of contamination,and after a few months if stored undercover in humid condition the water has come through the primer and is causing blisters in the top coat which required the car to be put back into an oven to bake them out. or worse still a strip back and repaint,So if you can avoid it use dry paper.

Thats interesting, and to be honest does make sense, i am sure filler primer would soak it up. i will try that, as for putting them out in the sun,it has been bucketing it down for about 2 days here in sunny Essex!!!

Yes, food for thought, I have always used the paper wet to avoid clogging and scratches and have had no apparent problems, but as primer is not waterproof I can see the logic in the suggestion. I suspect maybe folk have been too keen to get the top coat on and not let the primer dry out, as the paper is designed for wet use as well as dry.