Paint Spraying

cougar

cougar

Well-known user
May 6, 2010
718
62
staffordshire
I've been trying to prepare a part for the cougar ready for spraying but it's not gone well.

The part was already in the right colour but was scratched. The scratches were sort of like where the paint had chipped off. The primer below wasn't scratched. I started with 180 wet and dry wet on the chipped areas to blend them in, I then went over the whole item with 320 wet and dry to remove laquer etc.

After serveral hours of sanding it looked good enough to me so I thought I'd have a quick go with some primer to see what it looked like.

I had a quick look through the shelf in the garage to see what I could find and found a tin of "Filler Primer". The spoiler was quite warm as I'd been sanding it inside, so I thought I'd give it a try. It seemed to spray on perfectly - no runs and was looking nice and flat, but then as it started to dry it started to craze. The first patch appeared and I thought that perhaps I'd missed some laquer, but then a second patch appeared on a bit that I'd rubbed down to primer - so it shouldn't be that.

Any ideas on what I did wrong?

Maybe sprayed to much?


I've left it to dry fully, then I'll have to get the wet and dry on it again.
 
Did you use a prepsol before applying the primer filler and let it dry fully?

If it's a paint reaction between the previous coats and the primer filler (incompatible paints) you will need to sand it all right back as the reaction will have affected the original paint and maybe even the primer underneath that.
 
No I didn't use any sort of panel wipe. I had only just rubbed it down and gave it a good dry with a clean microfibre cloth.

The filler primer said:

Provides a tough durable protective coating
Advanced acrylic based formulation
Apply to existing paintwork or bare metal
Compatible with virtually all types of automotive paint
Can be used on cellulose finishes
 
First question would be: How old is the paint? Second, how long did you shake it for? (I take it, it's a rattle can?), you might be better off using a proper primer, rather than a primer filler. With some paints and primers, it's best to warm the can slightly, you can do this but just putting it into a bucket of warm water and then shake really well prior to spraying.
 
From experience, regardless if the spoiler was warm, conditions have to be pretty right, If it's slightly damp in the air it will cause this, also the spray has to be warm, the surface has to be prepared properly and cleaned first with a Tack cloth..
If it has attacked the paint underneath then it will need sanding right back and starting from scratch to be honest chap..
 
Iirc, acrylic is not compatible with 2xpack/laquer. Get a can of cellulose grey primer. Wet sand the job again, then get hold of some panel wipe to clear any contaminants. Let that dry, then spray the primer directly onto the prepped area very thinly for the first coat then gradually build it thicker with subsequent coats. If it's a spoiler, and it still reacts, rub it down completely and start from scratch, it could save a lot of time and hassle, plus, you'll have a uniform finish at the end of it.
 
Oh the joy of more sanding o_O :laugh:


what's a tack cloth?

I was shaking the can for about 5 mins so it was well shaken. The can was however straight from the garage where it has sat for probably 3 years or so. The garage was fairly warm (it's an integral garage rather than detached)
 
cougar said:
Oh the joy of more sanding o_O :laugh:


what's a tack cloth?

I was shaking the can for about 5 mins so it was well shaken. The can was however straight from the garage where it has sat for probably 3 years or so. The garage was fairly warm (it's an integral garage rather than detached)
Click to expand...

If it's 3 years old, paint may have gone off inside the can, especially after last winter, as I bet the garage got a bit damp/cold then didn't it??
 
cougar said:
Oh the joy of more sanding o_O :laugh:


what's a tack cloth?

I was shaking the can for about 5 mins so it was well shaken. The can was however straight from the garage where it has sat for probably 3 years or so. The garage was fairly warm (it's an integral garage rather than detached)
Click to expand...

A tack cloth is a sticky cloth that will remove and grease and dust prior to spraying chap.. it's pretty much a must if you want the paint to stick properly..
Also remember most spray shops are really warm, even if the garage is a inside kind of one it may just be below temp and the paint may not have had time to warm up.. and moisture in the air will cause a problem when spraying too...
 
Thanks for all the replies,

Just been a checked on it and more has crazed since leaving it, in general the crazed areas are the areas I didn't sand, so it look like it's more of a reaction than a temperature thing.

I'll sand it all down I think as per the suggestion above just to be safe.

Then I'll try all the suggestions above to improve my chances.


Is the tack cloth instead of panel wipe or as well as?


The garage doesn't get damp and never got 'that' cold last year, it's not the warmest part of the house obviously but last year I was redoing the utility room so the washer was in the garage and never froze etc like some peoples did.

Any tips to speed up the sanding process as I've now got a lot more to do and the bits I did do took a fair amount of time!
 
cougar said:
Thanks for all the replies,

Just been a checked on it and more has crazed since leaving it, in general the crazed areas are the areas I didn't sand, so it look like it's more of a reaction than a temperature thing.

I'll sand it all down I think as per the suggestion above just to be safe.

Then I'll try all the suggestions above to improve my chances.


Is the tack cloth instead of panel wipe or as well as?


The garage doesn't get damp and never got 'that' cold last year, it's not the warmest part of the house obviously but last year I was redoing the utility room so the washer was in the garage and never froze etc like some peoples did.

Any tips to speed up the sanding process as I've now got a lot more to do and the bits I did do took a fair amount of time!
Click to expand...

Panel wipe and tack cloth do the same thing, so you can do one or the other.

Re: Sanding - are you doing by hand? or have you an electric sander?? electric is easier and makes it a little quicker.
 
By hand, I've got a couple of electric sanders but I'd guess at them being too big/too rough.

I'll have a quick look to see if I can find a cheap enough tool which will do the job - any recommendations? Could be air or electric


Dual Action Sanders seem to be the most common for this purpose - would I be best to go for one of these? There seems to be some good air ones on ebay for not too much money. I guess then I need special sheets for them too.
 
cougar said:
Thanks for all the replies,

Just been a checked on it and more has crazed since leaving it, in general the crazed areas are the areas I didn't sand, so it look like it's more of a reaction than a temperature thing.

I'll sand it all down I think as per the suggestion above just to be safe.

Then I'll try all the suggestions above to improve my chances.


Is the tack cloth instead of panel wipe or as well as?


The garage doesn't get damp and never got 'that' cold last year, it's not the warmest part of the house obviously but last year I was redoing the utility room so the washer was in the garage and never froze etc like some peoples did.

Any tips to speed up the sanding process as I've now got a lot more to do and the bits I did do took a fair amount of time!
Click to expand...

I have a mouse sander i have used in the past which has given good results, but you can't beat hand sanding using a block or cork.. if you want to speed things up then a mouse sander with the right grit paper will help chap..
 
Panel wipe is a mild chemical cleaner which removes grease and other contaminates..silicone etc.
Tack cloths are just a sticky cloth that removes dust.

I've used primer filler on before..if you attempt to put it on too thick in one coat it will craze.

Temperature isnt a massive factor in paint reaction..unless you are spraying in freezing conditions then all that will be affected is the finish..if the paint is cold in the can then it doesnt mist nicely, it comes out in blobs.

The Part being sprayed doesnt need to be that warm either..if its too warm the paint dries too quickly and doesnt get chance to smooth out.
 
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