Classic cars forum & vehicle restoration.

[baconsdozen]

I've a vehicle that has been resprayed a time or two. On one panel there are a couple of fine hair line cracks in the paint. They've got no worse for the past couple of years but look bad as polish gets in them and dries white.
I don't really want to go down to bare metal (no time or garage at the moment) The paint isn't flaking and seems keyed well enough to the metalwork or primer,the cracks look like deep scratches.
Anyone any idea as to the cause?.

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Thirty years selling imperial hand tools for old machinery(Now happily retired).

[Bitumen Boy]

I can't help much on the paint itself - other than to suggest some kind of slow reaction that's caused the paint to shrink - but I wonder what polish you're using. I've been using this stuff for a while - http://www.bilthamber.com/wax-and-polishes/auto-balm - it's maybe not the best for ultimate shine but dries clear, lasts well and really does seem to have the anti-corrosion properties they boast about, on metals as well as paint. It's the only car polish that I've ever liked enough to buy twice and I reckon it would make those cracks a lot less visible if you could get the white deposits out first.

[baconsdozen]

That's a good idea,I have a bottle of the clear drying stuff (by turtle wax I think) somewhere in the shed.
As you suggest it would make them less noticeable.
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Thirty years selling imperial hand tools for old machinery(Now happily retired).

[mid]

i think there is generally a couple of reasons why it does this... usually its filler underneath that shrinks, but some paint just 'dries out' after decades in the sun etc and it shrinks and cracks - like a dried out river bed does. if it hasn't always been looked after with polish and waxes etc the UV gets to it.

[bob2]

can't you rub them down a bit and try filling them in just as a temporary measure?
you can use an artist painting brush and then some slight sanding with 2000 and some polish should see them looking a bit better and give a little more protection.

Bitumen Boy, that polish looks interesting, will have to purchase some from Bilt Hamber as I have used some of the other products they have and they are really good and do as they say!!

[ukdave2002]

There are coloured polishes, that will make paint defects less noticeable.

I'd be tempted to; treat any bare metal with phosphoric acid, stopper the gap , prime and paint with a rattle can (most paint suppliers will mix a rattle can to match your paint), if you spry with an arc, the paint can be blended in. If the original paint is clear over base, cut the clear back over a larger area, treat and paint the colour as before with an arc and then clear coat the whole area.

Dave

[baconsdozen]

Thanks for the suggestions.
I've sort of combined all of them and so far it's looking good,I'll post some pics later.
The paint was very thin not as thick as I thought. I think as someone suggested it's just very old and dried right out.
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Thirty years selling imperial hand tools for old machinery(Now happily retired).

[Rootes75]

Looking at the comments, does filler 'shrink'? I have a section on the front of a lorry cab that I am restoring that has mis-shapen so much it has needed quite a depth of filler.

[mid]

i think its more a case of it expanding and contracting at different rates to the surrounding metal rather than actually shrinking. its best practice to use as little thickness as possible and also directly onto bare metal rather than on top of any existing paint.

[Desert Fox]

Excessive paint thickness / expansion and contraction of panel = cracks.