# resprayed paint defects after a year



## hulsmeier (Jul 5, 2013)

Hi,
This is my first time posting here, I usually use theminiforum, but I thought this site would have a better idea as to my problem. 

I resprayed my car just over a year ago, however just around winter, I noticed some crack like defects occurring in the paint. There was also pimples. I used a car cover over the winter so I have a feeling that's partly to blame for the pimples. 

When respraying I used a bar coat the cellulose primer filler, then cellulose top coats. 

Does anyone have any idea as to why these defects have occurred? 

Thank you in advance.


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## XRDAN (Feb 28, 2012)

the cracks look like a reaction, ive had very similar effect using a cellulose primer, it came up instantly though so I could rectify before top coat. I did'nt use a bar coat tho so does seem strange in your case but i can only think its the primer reacting. the pops are more than likely moisture in the air line, did you use a oil/water trap?

Dan


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## nick_mcuk (Jan 4, 2008)

Those cracks are not caused by the car cover....that's a reaction from having too much paint on there.

As for the small blisters thats from moisture in the compressed air, you also sometimes get it round the edge of "filled" areas where moisture gets trapped in the filler.

The only way to fix both is flat and respray.


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## Mondeo220 (Apr 19, 2010)

hulsmeier said:


> Hi,
> This is my first time posting here, I usually use theminiforum, but I thought this site would have a better idea as to my problem.
> 
> I resprayed my car just over a year ago, however just around winter, I noticed some crack like defects occurring in the paint. There was also pimples. I used a car cover over the winter so I have a feeling that's partly to blame for the pimples.
> ...


This is called crazing, its caused by solvent being trapped under the layers of paint when you painted it, usually because of incorrect flash times and too heavy an application between coats. You also have visible blisters visible in those pictures.

The problem with air drying paint is just that, its air drying, and must be able to dry sufficiently between coats, this happens with the primer too if not more so because the build is thicker.

I did an MG Midget last week which had blistered, rust spots were forming under the blisters when i stripped the paint off to bare metal. Unfortunately the only cure is to strip right back to metal and start again, use an etch primer first and observe the data sheet for the paint you are using with regards flash off times, thinner ratio and humidity etc.


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## steveo3002 (Jan 30, 2006)

blisters may be the car cover

cracks can happen if they painted over something iffy , when the sun warms it the underlaying paint may have softened and moved around and the hard topcoat doesnt move at the same rate so cracked


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## hulsmeier (Jul 5, 2013)

Thank you, for the replies. No oil/water trap was used, so I think you're right about the moisture side of the defects. 
If I was to respray using cellulose again, how can I avoid this occurring again? I didn't use that many coats of paint the last time, however I think the flash times may have been too short, and possibly the paint went on too thick?. The cracks took over a year to set in too.
Thanks again!


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## XRDAN (Feb 28, 2012)

hulsmeier said:


> Thank you, for the replies. No oil/water trap was used, so I think you're right about the moisture side of the defects.
> If I was to respray using cellulose again, how can I avoid this occurring again? I didn't use that many coats of paint the last time, however I think the flash times may have been too short, and possibly the paint went on too thick?. The cracks took over a year to set in too.
> Thanks again!


with celli the flash of times pretty quick so lots of light coats will give the best results. use a heat gun between coats- u will be able to tell when the solvents have evaporated and straight on with the next. I would do 4-5 light coats and a final wet coat

cheers


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## Aaran (Sep 18, 2007)

get 2 water/air filters in that line (end of compressor and end near the gun) 

also if you have hard line pipeing from the compressor build a steep incline from the tank, then a very steel drop (half way off this drop branch off to an exit for an airline) and on the bottom fit a manual drain valve. do this as many times as yoou can the longer it is the more it will cool the air and the less moisture at the gun end.

you need to get the compressed air to cool , having vertical bits in the pipeing will allow and condensation.moisture in the charge air to run back down the pipe, (hence the drain in the other drop, just empty it daily) 

in an ideal world if you paint alot invest in an Air dryer (its basically an air con unit that force cools the air and separates any moisture out of it) so your pretty much never spraying with water out of the gun.


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## Aaran (Sep 18, 2007)

http://www.mig-welding.co.uk/air-system.htm


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## hulsmeier (Jul 5, 2013)

thanks again for the help! feeling a lot better about spraying the car again and will definitely take your suggestions into consideration.


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