I primed my LH and found several small cracks & some flakeing on corners and crevices etc. Is this caused by the Primer not being thinned down enough? (I'm painting acrylic Primer)
CRACKING IN PRIMER
Started by
Orleans
, Mar 24 2010 06:00 PM
34 replies to this topic
#1
Orleans
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Posted 24 March 2010 - 06:00 PM
#2
_Bomber Watson_
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Posted 24 March 2010 - 07:08 PM
No generally that is caused by you putting it on wrong.
Ima need a whole lot more info, tell me EXACTLY what you did, and i may be able to tell you where it went pear shaped.
Cheers.
Ima need a whole lot more info, tell me EXACTLY what you did, and i may be able to tell you where it went pear shaped.
Cheers.
#3
_beergut_
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Posted 24 March 2010 - 07:15 PM
number of things poor prep/enemal under the paint are the main ones i can think of
but bomber will set you on the right track
but bomber will set you on the right track
#4
TerrA LX
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Posted 24 March 2010 - 07:16 PM
Nothing wrong with the primer.
POOR PREPARATION!!!
POOR PREPARATION!!!
#5
Orleans
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Posted 25 March 2010 - 07:42 AM
I wasn't there when my mate did this recent spray of Primer & guide coat, but prior to that it had a coat of Sanded back (240) Primer and before that the car was in spray putty (sanded back 240).
[attachment=7174:PrimerS (2).JPG][attachment=7175:PrimerS (3).JPG]
And knowing my friend who did this, "it was nothing wrong that he did."
[attachment=7174:PrimerS (2).JPG][attachment=7175:PrimerS (3).JPG]
And knowing my friend who did this, "it was nothing wrong that he did."
Edited by Orleans, 25 March 2010 - 07:54 AM.
#6
Heath
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Posted 25 March 2010 - 08:56 AM
What did it look like underneath? And why does that finish look so grainy? Was it thinned down properly and actually wet when it hit the panel? lol
#8
_Bomber Watson_
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Posted 25 March 2010 - 09:07 AM
Heath is thinking what im thinking, what did you use to reduce the primer, metho?
Finish should be reasonably smooth, perhaps a tad peely, in acrylic, not look like 36 grit sand paper. Obviously you have been using to fast a thinner and/or holding the gun to far away and/or not enough volume.
The crack can only be for a couple of reasons really, first the primer has been put on to thick and cracked as it shrunk, and second the primer was put over an unsuitable substrate.
With acrylic i would lean toward the second. Now its time to play 21 questions.
Was the primer under it the same type?
Was the brand of spray putty (horrid horrid shit) the same brand?
What was the spray putty (horrid horrid shit) put over?
Are you using spot filler? If so what brand/type?
What drying times have you been giving everything, IE
between coats,
before sanding,
with spot filler how long have you been letting it flash.
Has any filler been put on the car then allowed to get wet (rain etc)?
Has the primer been alowed to get wet(rain, etc)?
When wet rubbing (not recommended until final prime) have you been working on one area at a time then drying it before going onto the next?
Answer all those questions and we may have a solution for you.
Finish should be reasonably smooth, perhaps a tad peely, in acrylic, not look like 36 grit sand paper. Obviously you have been using to fast a thinner and/or holding the gun to far away and/or not enough volume.
The crack can only be for a couple of reasons really, first the primer has been put on to thick and cracked as it shrunk, and second the primer was put over an unsuitable substrate.
With acrylic i would lean toward the second. Now its time to play 21 questions.
Was the primer under it the same type?
Was the brand of spray putty (horrid horrid shit) the same brand?
What was the spray putty (horrid horrid shit) put over?
Are you using spot filler? If so what brand/type?
What drying times have you been giving everything, IE
between coats,
before sanding,
with spot filler how long have you been letting it flash.
Has any filler been put on the car then allowed to get wet (rain etc)?
Has the primer been alowed to get wet(rain, etc)?
When wet rubbing (not recommended until final prime) have you been working on one area at a time then drying it before going onto the next?
Answer all those questions and we may have a solution for you.
#9
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Posted 25 March 2010 - 01:46 PM
Believe it or not I have applied primer with a paint brush and a roller, it is pretty hard to frOck it up unless you go too thick.
Im stil going with preparation.
In the picture above, did it crack over a seam or joint?
Im stil going with preparation.
In the picture above, did it crack over a seam or joint?
#10
Orleans
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Posted 25 March 2010 - 05:57 PM
Thanks everyone.
As I first said, I don't think there was enough thinners used.
Q &A
Was the primer under it the same type?
--Yes, From the same can.
Was the brand of spray putty (horrid horrid shit) the same brand?
--Yes, same brand.
What was the spray putty (horrid horrid shit) put over?
--Sanded back acrylic paint.
Are you using spot filler? If so what brand/type?
--Haven't used any yet.
What drying times have you been giving everything, IE
between coats. --Days.
before sanding. --Days.
Has any filler been put on the car then allowed to get wet (rain etc)?
--No (cracks are not where filler is).
Has the primer been alowed to get wet(rain, etc)?
--No. Car is garaged.
When wet rubbing (not recommended until final prime) have you been working on one area at a time then drying it before going onto the next.
--Havn't wet rubbed yet.
Thanks for helping Bomber (it's funny you say Spray putty is horrid shit - my mate (panelbeater) loves it!) Think I'll continue on without him. I'm a mechanic. I've never sprayed anything before!
As I first said, I don't think there was enough thinners used.
Q &A
Was the primer under it the same type?
--Yes, From the same can.
Was the brand of spray putty (horrid horrid shit) the same brand?
--Yes, same brand.
What was the spray putty (horrid horrid shit) put over?
--Sanded back acrylic paint.
Are you using spot filler? If so what brand/type?
--Haven't used any yet.
What drying times have you been giving everything, IE
between coats. --Days.
before sanding. --Days.
Has any filler been put on the car then allowed to get wet (rain etc)?
--No (cracks are not where filler is).
Has the primer been alowed to get wet(rain, etc)?
--No. Car is garaged.
When wet rubbing (not recommended until final prime) have you been working on one area at a time then drying it before going onto the next.
--Havn't wet rubbed yet.
Thanks for helping Bomber (it's funny you say Spray putty is horrid shit - my mate (panelbeater) loves it!) Think I'll continue on without him. I'm a mechanic. I've never sprayed anything before!
#11
Orleans
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Posted 25 March 2010 - 06:27 PM
I used a macro lens to get those close pics also - the cracks are only about 1 inch long. The finish isn't as rough as those pics make out.
#12
_beergut_
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Posted 25 March 2010 - 06:39 PM
rub it back and start again
remember to prepsol it and clean the s#$t out of it
and if it cracks again then you have enamel/2 pack/silicone somewhere
oh and remove alll your silicone based products to another shed
aycrillic HATES sillycone in any form lol
remember to prepsol it and clean the s#$t out of it
and if it cracks again then you have enamel/2 pack/silicone somewhere
oh and remove alll your silicone based products to another shed
aycrillic HATES sillycone in any form lol
#13
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Posted 25 March 2010 - 09:59 PM
Cracks in primer like that come from the primer being applied too heavily per coat. Bomber is correct in what he said in that the primer shrinks and cracks open. It usually occurs where paint has a chance to pool like in body lines,crevices etc.
It's not a slur on the bloke who put it on, we've all gotten a bit carried away from time to time particularly when your trying to build up/make good on crap panel work given to you by overrated panelbeaters....sorry for the rant....it's just accidental, it can be feathered out until its stopped lifting/cracking and spot primed to rectify it.
It's not a slur on the bloke who put it on, we've all gotten a bit carried away from time to time particularly when your trying to build up/make good on crap panel work given to you by overrated panelbeaters....sorry for the rant....it's just accidental, it can be feathered out until its stopped lifting/cracking and spot primed to rectify it.
#14
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Posted 25 March 2010 - 10:12 PM
& some flakeing on corners and crevices etc.
#15
_gtr161s_
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Posted 27 March 2010 - 11:32 AM
I had a similar problem...short of completely removing the old substrate I used barcoat (isolator) over the suspect area then primed as per normal..problem solved.
#16
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Posted 28 March 2010 - 05:32 PM
i'm going with poor prep
rub it back prepsol it(solvent based wax and grease remover is now detergent based)
wipe it off with a tack rag and reprime
and buy a good compresser and spray guns those airosol things end up costing more to do a whole car
rub it back prepsol it(solvent based wax and grease remover is now detergent based)
wipe it off with a tack rag and reprime
and buy a good compresser and spray guns those airosol things end up costing more to do a whole car
#17
Orleans
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Posted 29 March 2010 - 07:39 AM
Good compressor...?
Edited by Orleans, 29 March 2010 - 07:40 AM.
#18
_beergut_
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Posted 30 March 2010 - 09:44 PM
yeah not the merc kompresser that costs 60 gees or so
#19
_Bomber Watson_
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Posted 30 March 2010 - 10:03 PM
Isnt that a Kompressor???
I just got back from my melb trip, i'll comment on the actual problem when im sober and have re read all the replies a few times.
Cheers.
I just got back from my melb trip, i'll comment on the actual problem when im sober and have re read all the replies a few times.
Cheers.
#20
_freddy_
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Posted 31 March 2010 - 07:51 AM
have you got a water trapment thing that goes in between compressor and spray gun?
wen i had probs with primer sum other panels i found out i was usein the wrong thinners them was told to thin at 4 parts primer to 1 part hardener but the primer had thinners already in it from where i brought it.
wen i had probs with primer sum other panels i found out i was usein the wrong thinners them was told to thin at 4 parts primer to 1 part hardener but the primer had thinners already in it from where i brought it.
#21
Orleans
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Posted 31 March 2010 - 12:24 PM
I've got a 32cfm/120 ltr compressor with two water seperators. It wasn't that.
This pic below is one of the cracks around the boot channel. The other cracks were in the door sills.
[attachment=7238:PrimerS (3).JPG]
I've sanded them back to bare metal. Hoping they don't reappear...
Oh, I fired my friend John, who was painting my car for me. Now I hope I don't frOck it up from here on in.
Have no experience with a spray gun... but I should by the time I've finished this project!
This pic below is one of the cracks around the boot channel. The other cracks were in the door sills.
[attachment=7238:PrimerS (3).JPG]
I've sanded them back to bare metal. Hoping they don't reappear...
Oh, I fired my friend John, who was painting my car for me. Now I hope I don't frOck it up from here on in.
Have no experience with a spray gun... but I should by the time I've finished this project!
#22
_Bomber Watson_
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Posted 31 March 2010 - 12:54 PM
Start with the primer mate. Its pretty easy, just try to get the technique right at this stage.
Cheers.
Cheers.
#23
_MR LJ 1972_
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Posted 02 April 2010 - 09:39 PM
Hi mate, new to the forum, looked at your thread and thought i could help you out, i have had a few similar problems in the past, i have built a few toranas, the only way to rectify it is to take it back to metal, which you say you have done, you can chance putting an isolator over it, then a re prime or hi fill, but that is only a short term fix, if you do that once the car is painted (in colour) then exposed to weather regardless hot cold wet or dry, or how long after you've painted, acrylic takes a long time to fully cure despite the fact people think it cures after two or three weeks it will take a good three months before it stops shrinking. i'll tell you why. Acrylic is a soft paint, it has more tolerance to hot and cold than 2 pac, therefore it will expand and contract further than 2 pac. Ever seen paint jobs where the clear peels. This is only caused by a few reasons, 1. some one has painted a 2 pac clear over acrylic to escape buffing (this is ok to areas not exposed to extended UV light), 2. too much hardner is mixed into 2 pac clear or excessive base coat colour coats will cause clear coat to delaminate causing the clear to peel. I suggest take your time you only want to paint it once, mix the primer accuratley (specs should be on the paint tin) let the primer cure properly an extra week here or there wont hurt you as much as having to paint it again, and if you want a tip, if you have bare metaled the car use an etch primer first. cheers
#24
_Bomber Watson_
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Posted 02 April 2010 - 09:59 PM
Yep, you seem to know a tiny bit about painting, bugger all about 2k's, and not much of whats going on here. I made nothing out of that post...
Your reasons for Peel are correct but not the only ones, there are about a hundred more, and although yoru correct that acrylic doesnt stop shrinking for three months it NEVER actually cures.....
Etch is a good idea over bare metal, but do you know why?
And we ARE talking about Acrylic here....
Your reasons for Peel are correct but not the only ones, there are about a hundred more, and although yoru correct that acrylic doesnt stop shrinking for three months it NEVER actually cures.....
Etch is a good idea over bare metal, but do you know why?
And we ARE talking about Acrylic here....
#25
_MR LJ 1972_
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Posted 03 April 2010 - 06:39 PM
Yep, you seem to know a tiny bit about painting, bugger all about 2k's, and not much of whats going on here. I made nothing out of that post...
Your reasons for Peel are correct but not the only ones, there are about a hundred more, and although yoru correct that acrylic doesnt stop shrinking for three months it NEVER actually cures.....
Etch is a good idea over bare metal, but do you know why?
And we ARE talking about Acrylic here....
Talking about Acrylic, cause the thread actually started regarding a problem with ACRYLIC PRIMER. (check the thread starter)
Sorry about the detail, it must of got confusing for you, totally understood what was going on in the thread and yes you are right there are many more reasons for peel and cracking, fry up, delamination etc.....etc...... O'h your also right about me knowing a tiny bit about painting, i have been doing it for about 18 years, both Acrylic and 2k, Etch primer is not mandatory but it does provide very good adheasion to bare metal surfaces and reduces the risk of fry up in the paintwork when it's applyed over a repair for following coats . In the panel shop which i am head painter we have both systems cause people who want their resto jobs to look original choose Acrylic rather than 2k.
and besides don't we join forums for a chat and maybe to help someone out because they share a similar passion, cause that's what i thought. Not to have forum cowboys have a half assed crack at putting you down. when your trying to help someone out.
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