Hard top blistering!

[Misterb_57]

The F's hardtop is blistering in the paint/gel coat finish and it appears to be getting worse as the winter wears on.

I'm guessing this is a form of osmosis, as when burst they emit water.

Has any experienced this before and if so what causes it and what can be done about it - it is dry stored in the summer.

Chris.

[Rob Bell]

New one on me - mine's 15 years old, stored in summer (but spent the last two winters in the garden shed!!!), but nothing like that's happened to mine. It's GRP - and I bet there is a forum somewhere that deals with GRP (boat builders perhaps?) that will know what the problem is and how to solve it!

Hopefully someone knowledgable in things GRP can inform us, and do let us know if you find anything out!

[pipster101]

Funnily enough I was going to post up about this too. I haven't had my MGF long so I thought that all the blistering over the hard-top was some sort of tar or fallout debris, so that it would come off with either a tar remover or some clay. But the blisters are solid and don't seem to be effected by the tar remover. There's a LOT on my hard-top, plus I noticed one on my wing-mirror too. What do people think are causing them?

Cheers, Jonathan

[David Clelland]

What colours are your hardtops that are blistering - have they been painted? I've had my black Heritage one for about 10 years now and it's fine. Like Rob I hardly ever use it now and it's been hanging in the garage for the last 3 years without going on the car.

[pipster101]

Well, mine's in the original black. How it's been kept in the past I've no idea, although not very well judging by the chips on the front edge and the fact that the headlining had no lining!

By the way, boring question - I love the picture of your car - but how do you keep your brake discs looking so shiny and new?! I have new discs and they've been going slightly rusty. Even after a good clean of my alloys with wheel cleaner, which also cleaned the brake calipers (which have then started to corrode a little again) the discs never came up clean. Are you spraying them with brake disc cleaner?

Cheers

[Canalsman]

The F's hardtop is blistering in the paint/gel coat finish and it appears to be getting worse as the winter wears on.

I'm guessing this is a form of osmosis, as when burst they emit water.

Has any experienced this before and if so what causes it and what can be done about it - it is dry stored in the summer.

Chris.

As a former GRP boat owner I know a little bit about this.

It's unlikely that a GRP hardtop would suffer from osmosis. Boats suffer from this when the gel coat is imperfect and water permeates into the substrate - but this will only happen with permanent immersion in water.

When a GRP boat is taken out of water, blisters may appear when the water trapped in the substrate tries to make for the exit.

If a boat is suffering from GRP osmosis, it has to be taken out of water for as long as required to dry out. Then treatment can begin. If the substrate isn't dry, any treatment that's undertaken just seals in the moisture, till it finds another way out.

It is curious that you say the blisters contain water though. I suppose if the hardtop has at some point been stored in an ultra humid environment it may have taken up water through the gel coat.

[David Clelland]

By the way, boring question - I love the picture of your car - but how do you keep your brake discs looking so shiny and new?! I have new discs and they've been going slightly rusty. Even after a good clean of my alloys with wheel cleaner, which also cleaned the brake calipers (which have then started to corrode a little again) the discs never came up clean. Are you spraying them with brake disc cleaner?

Cheers

Sorry no black magic I'm afraid. I just use the brakes and that keeps the disc surface shiny. When they were new I painted the centre part of the discs (the bit that usually goes rusty) to keep them looking good. I never use alloy cleaner - all I do is polish the wheels and then wash them at the same time as the rest of the car.

[daz41]

hi chris,

would it be possible to post some pic's

cheers
darren

[pipster101]

I just use the brakes and that keeps the disc surface shiny. When they were new I painted the centre part of the discs (the bit that usually goes rusty) to keep them looking good. I never use alloy cleaner - all I do is polish the wheels and then wash them at the same time as the rest of the car.

Yes, I know that use is supposed to keep them clean but mine seem to rust over again very quickly and the back ones never seem to clean up at all - a bit of a pain, maybe it's my damp garage!

[pipster101]

would it be possible to post some pic's

I'll pop up and get some of mine this afternoon to see if we're talking about the same thing...would be handy to know what's going on.

Cheers

[Canalsman]

... maybe it's my damp garage!

There's nowhere worse to keep a car than a damp garage.

That has been proven over the years to hugely accelerate corrosion of all kinds.

Much better to keep the car on the drive or on the street ...

[Misterb_57]

I'll take some pics tomorrow and post.

My HT is black and as I don't know its history I cant vouch for its previous storage but it general condition is good for 10 years old (assuming its as old as the F).

My garage is pretty dry and aerated, as my A restoration project with virtually no paint, can vouch for -so I'm pretty sure the problem does not lie there.

Canalsman - thanks for clearing up the osmosis theory. Clearly it has not been submerged but could it be down to faulty manufacture?

I'm considering flatting it back and respraying it, so do you guys have any advise as to which primer/sealer to use?

[pipster101]

... maybe it's my damp garage!

There's nowhere worse to keep a car than a damp garage.

That has been proven over the years to hugely accelerate corrosion of all kinds.

Much better to keep the car on the drive or on the street ...

That backs up what the AA man said to me. I've been struggling to find another garage, that's the problem and I don't think that the missus would be too keen on the hard-top/spare alloys/cleaning products/various bits cluttering up our conservatory!

[Rob Bell]

From what Canalsman has said (very helpful, thanks!) I am starting to doubt that this problem is osmosis. Perhaps as you say Misterb, its more likely to be a manufacturing fault? In which case rubbing down to the substrate and reapplying a gel coat and prepping for paint is going to be the best bet.

I wonder whether this is a problem that is going to be more common on black hardtops that are coloured in their gel-coat, rather than the ones that are painted (and sealed?) in body colour?

[Misterb_57]

Here we go - a picture

[Misterb_57]

and another one....

Has anyone out refinished one of these before?

[David Clelland]

I've seen blisters like that on an MGB that had a respray. Has the hardtop possibly been painted black at some time and that's what's causing the problem. Hard to tell from the pictures but the finish looks a little "orange peel'd". The finish on my hardtop looks much smoother.

[Canalsman]

That doesn't look like osmosis at all to me.

Especially since some of the blisters are elongated.

I reckon it's just poor paint adhesion - perhaps some silicon found its way onto the surface before repainting ...

[pipster101]

I haven't managed to take a picture yet, but that's what mine looks like too - although I don't have any long elongated ones. Small hard bubbles, that don't seem to flex or have any give in them. Odd! Will take a piccy today. Cheers