Bodywork gurus (Mike007?), have a paint problem.

**SimonP** · 23-04-2005 23:35

In the process of respraying a grille due to the old one breaking off on the Cavalier.

First off, I did a light strip back to use old paint as a base for top coat. Unfortunately, there was quite a bit of silicone in the old paint and it blistered. So waited for it to dry and sanded it back a lot more. Cleaned thoroughly with spirit.

It did almost the same again, although not as bad. So I stripped it back to almost the plastic and used a separate primer.

All went on well apart from one section in the middle of the grille. It blistered back a bit again. Even with primer. Anyway, I sanded that back again and used primer to build up layers as a high build primer. It then went a bit wrinkly. So I left it dry and sanded it back look ok-ish. but after cleaning with water I noticed it bead a bit in that area. So dried it and tested with primer again and it started to blister again.

Any ideas what to do? It's just this one area, but it's slap bang in the middle of the grille. I thought it might be a reaction with the old paint. But it only does it in this area.

**Mike007** · 23-04-2005 23:41

Hmmm, that's a tricky one. To be honest, I'm not sure. Does the primer look OK before the topcoat goes on? You might have a problem now that you have too much primer without allowing enough tmie for each coat to dry, so you have solvent entrapment.

To be honest, I would strip that section back to plastic, spray with plastic primer and then prime/topcoat as normal. It might be the only way to rectify it.

Mike (bodywork guru

)

**SimonP** · 23-04-2005 23:44

Cheers

That what I was thinking. I think there are foreign solvents underneath that haven't dried properly. I will be stripping that area back again totally tomorrow.

I have a basic primer which is suitable for plastics although not a true 'plastic' primer. It should suffice for this area as I only took it back to bare plastic in a few small areas.

**angryman** · 23-04-2005 23:50

Originally Posted by SimonP

Cheers

That what I was thinking. I think there are foreign solvents underneath that haven't dried properly. I will be stripping that area back again totally tomorrow.

I have a basic primer which is suitable for plastics although not a true 'plastic' primer. It should suffice for this area as I only took it back to bare plastic in a few small areas.

You really need plastic primer for grills etc. Rub it all down with 1200 grit wet n dry and loads of warm soapy water. Rinse thoroughly and leave to dry overnight
Remember original paint is different to can paint and will behave differently when sprayed over

**SimonP** · 23-04-2005 23:51

Didn't have this problem with my mirror housings though. I'll do another test run with what I have and see what the results are.

**Aragorn** · 23-04-2005 23:51

dont use white spirit

its oil based and leaves residue behind

use brake cleaner or panel wipe which are based on xylene (i generally have a can of brake cleaner kicking around so i use that

**SimonP** · 23-04-2005 23:52

Originally Posted by Aragorn

dont use white spirit

its oil based and leaves residue behind

use brake cleaner or panel wipe which are based on xylene (i generally have a can of brake cleaner kicking around so i use that

I wash the spirit off after with water with copious amounts of fresh water, so there's nothing left on the prepped area.

I must get some decent bodywork degreaser and a dispencer.

**Mike007** · 23-04-2005 23:52

Si, have a look on the back of the grill and see if you can find what plastic it is. There is a fair chance that it is ABS which actually has reasonable adhesion, so while I wouldn't normally recommend it, you can probably get away with the primer you have.

Mike

**SimonP** · 23-04-2005 23:53

It is ABS for sure. I know that from working with it.

**Mike007** · 23-04-2005 23:57

Well, don't tell anyone I said so, but you should be OK

. A plastic primer would be the ideal though.

Mike

**angryman** · 23-04-2005 23:59

Originally Posted by SimonP

I wash the spirit off after with water with copious amounts of fresh water, so there's nothing left on the prepped area.

I must get some decent bodywork degreaser and a dispencer.

I'd say it could be the spirit doing it. On the mirror housings and grills (one spare) i have done all I have used before painting is warm soapy water and the 1200 grit.
Not sure just clean water will get all the spirit off

**SimonP** · 24-04-2005 00:07

I got desprate which is why I used the spirit, wanted something that would break the silicone down under the old paint. Looks like some got soaked into the plastic I guess.

**Mike007** · 24-04-2005 00:10

It could be the white spirit, but that wouldn't really explain why it is isolated in one area. You could use petrol to wipe the panel down with. Panel wipe is mostly just a smallish, straight-chain hydrocarbon and so is similar to petrol.

Mike

**alistairolsen** · 24-04-2005 00:11

I normally use meths for cleaning, meths on a hard paper roll, so no left over dust. Seems to work well enough.

**SimonP** · 24-04-2005 00:11

I think it's because it blistered slightly in that area, I rubbed that back almost, if not to the plastic. That area of 'rough' plastic must have soaked some of the stuff up. Rest being dry etc...

**Kruger** · 24-04-2005 00:16

Deffinately a white spirit problem, doesnt white spirit eat into ABS???, just get some cheap panel wipe, its only about £5 for 5 litres from an auto paint supplies, and is also useful for cleaning stubborn stains and tar off almost anything.

I'd use 800 grit paper wet for knocking down the primer, then just give it a tickle with wet 1200. if its a solid colour though you could down to 400/500 dry.

Kev

**SimonP** · 24-04-2005 00:23

I'm using 800 as first stage anyway. Always wet. Might try some tougher grade on that area tomorrow, then feather out a bit. Should get at the plastic...I hope. Hope it's not damaged.

**Mike007** · 24-04-2005 00:26

ABS is fairly hardy so I'd have thought I'd be OK. Might be an idea to stick it in an oven at 60C or so for a while after rubbing it back just incase there is any solvent in the plastic.

Mike

**SimonP** · 24-04-2005 00:29

I've got a large fan heater I've been using, so shall use that. Can't get that in the Oven! Plus it's a gas one!

Run out of primer as well...don't you just hate that midway through a job!

**Mike007** · 24-04-2005 00:37

Oh yeah! I didn't think about the size!! LOL

Mike

**dogsy** · 24-04-2005 19:39

we quite regularly have this problem and never found out exactly what it is. i usually find that when using the primer, apply it in thin dust coats and use a hot air gun to dry each coat well. build it up using about 10 very thin dust coats and once that is dry use a slightly thicker top coat.

**Mike007** · 24-04-2005 21:29

The only problem with doing that is that you will lose a lot of the durability of the primer as it needs to form a cohesive layer with each coat to work properly.

Mike

**SimonP** · 24-04-2005 22:02

Thank feck for that! Finally finished it after 3 attempts. Totally stripped as much of the old paint off as poss. Difficult on plastic as it rubs away easily, causing loss of lines and what have you.

Spent ages on it today building up layers of primer, flatting back...repeating etc.

Managed to get a good base for it and the paint went on quite well. Used a whole can though. Bit of a lacquer run on the bottom edge but I managed to feather it back.

But considering it was bubbling and blistering originally, I am quite happy with the end result!

A dirty grille full of wax and silicone in the paint.

Just finished it. Just need the rubbers to fit on the top now.

**SimonP** · 24-04-2005 22:08

That's a really crap picture actually....here's a better one. Managed to get a good shine after flatting back.

**Mike007** · 24-04-2005 22:10

Glad you got it sorted in the end. It's certainly an improvement!!

.

So, what's next?

Mike

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