43 replies to this topic

[james962]

Im currently primering the front end of the mini.

First coat was applied with a compressor and spray gun, fine. Everything went smoothly. We let it dry for about 2hrs and then applied another coat. It appeared to go on fine until it started to dry, and then cracks appeared. Not very larger cracks, but still cracks, about 30mm in length. It also started to bubble around the window seal lip, along the top edge of where the wing is folded for the arch, and along the bonnet groove on the wings. The buuble are small in size.

We think it is a reaction, but don't know why. The places that it has occured dont make sense. Its cannot be lack of sanding as some of the places are on the new plates that dad made up. Its not the lacquer as this was sanded down easily to the previous primer.

We left it over night (last night) and went back to it this afternoon. We sanded down the bubble and cracks, then reapplied the primer to the offending parts. Within 5 mins of applying it, some of it came back, but not all of it Then, small cracks about 5mm in length appeared in different locations than before.

They all are either on lips, bottom of wing, wing groove for bonnet, window seal part, botton of roof rail. The wings are fine.

Some parts has started to flake as well, this is along the lip a the bottom of the wing.





james

p.s. also, we ruled out the cellulose thinner content of the primer applied as we bought some in a can to try, but no results.

Edited by james962, 27 March 2008 - 02:08 PM.

[WiredbyWilson]

this can happen if there is silicone in the air (wd40 etc etc) or if the area isn't keyed up properly to start.

was the mix of the 2nd coat the same as the original as this can cause a prob.

and not sure you need to leave it 2hrs between coats, just let it tack off which is prob about 15mins based on what i witness at the bodyshop i do - also means you can use the same mix of prmer.

just my thoughts on it

[Sleepy Stu]

Sounds like a case for the Panel_Beater_Peter

*shines the bodywork emergency light into the sky* (its a bit like the bat signal but has a mini on it instead)

Edited by Stewart_GT, 27 March 2008 - 06:24 PM.

[WiredbyWilson]

Sounds like a case for the Panel_Beater_Peter

*signs the bodywork emergency light into the sky* (its a bit like the bat signal but has a mini on it instead)

ROFL PMSL

is there an air raid siren too?

Edited by Wilson1275, 27 March 2008 - 02:16 PM.

[james962]

cheers

there was no silicon in the air, and the garage was ready for it, defo no dust or anything.

the mix would have been slightly different i guess, as the first was mixed for the spray gun. The second mix for the spray gun was only slightly more cellulose. This then made a small reaction, but only in a couple of places.

the odd thing was that it surely couldnt be the mix becasue there are no problems on the flat panels, i.e on the scuttle, on top of the wings.

These "defects" were sanded down, and then was primered with a ready mixed spray can and it has still peeled off.

hmmmm

james

lol @ siren

[WiredbyWilson]

sounds like you have mixed primer types which more than likely will react mate.

still awaiting the signal for pete lol

[midridge2]

before you primed the car the first time, did you use any panel wipe to remove any grease, wax etc?
i suggest flatting the primer down and wipe over with panel wipe and re prime, if it reacts again flat down and spray with isolator (bar coat)

[jack_marshall]

Its a reaction because you've left the primer too long before the next coat. It has basically started to cure so the next coat reacted.

You need to apply the coats as soon as they have flashed off, which is a matter of minutes if you in a warm area or booth.

Ideally you need to strip the primer back off, being careful not to ruin any filler work, and re-do it, applying coats quicker next time.

A DA sander would be quickest and easiest to strip the primer off. With some 320-500 sanding disks.

Good luck.

[mini_lad_1990]

Its a reaction because you've left the primer too long before the next coat. It has basically started to cure so the next coat reacted.

You need to apply the coats as soon as they have flashed off, which is a matter of minutes if you in a warm area or booth.

Ideally you need to strip the primer back off, being careful not to ruin any filler work, and re-do it, applying coats quicker next time.

A DA sander would be quickest and easiest to strip the primer off. With some 320-500 sanding disks.

Good luck.

follow this advise given to you BUT only sand it down by hand 90% of the time you will ruin the fillering underneath and have to do all that again!!!

[jack_marshall]

Yeah, know areas of filler are best done by hand.

But areas you know are only metal underneath, save yourself the time and use a sander.

[james962]

cheers for the advice chaps.

We thought it was a reaction of some sort, was just frustrating once we sanded it and primed it for it to curl up lol

I will probably be sanding it all down tomorrow

I suppose its better for it to happen at this stage rather than once ive put on the paint and lacquer


thanks again

james

[james962]

Just one other query:

We have only got reactions going on along edges and on inside corners. All the flat areas seem sound so far. i.e all over the wings, scuttle.

1) If we leave it for 24hours for it to fully cure, would it be safe to leave any areas where there is no visible reaction?
2) Would it really be necessary to strip it all and start afresh?
3) If we keep it on the flat parts that look sound, would it be likely that a problem will occur in the future?


james

[jonny d]

not worth the risk

[fastroadie]

-yeah take it off and start again, you should also try to stick to the same manufacturer as much as possible to reduce chance of reactions(if not use a sealer/isolator BARCOAT is good stuff),

-you only need about approx 8-10 mins between coats of primer, this means the layer soak into each other slightly and cure as one,

-also if you spray a thick coat this can sometimes crack when it dries.

-if you are buying from a specialist paint/panel shop, ask for the technical data sheet for the paint you buy removes the guess work.

Hope this helps dude and good luck.

[M1N1C00P3R1275]

hehe panel beater peter is reading yay