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MG Midget and Sprite Technical - bubbles in paint

I've just taken my '71 Sprite out from my daughters garage where it has been for the past 4 weeks. I have found that the paintwork on bonnet and bootlid appears to have measles. It looks like small (about 1mm) bubbles on the bootlid and larger (about 2mm) on the bonnet. The paintwork may not have been the best in the world but these were not there before I put the car away. we have had subzero temperatures overnight for a week or so now though. I think the bubbles may have water under them. Not looked with an eyeglass yet but certainly some liquid is expelled if I press with a fingernail. I have had the car for 3 years and not seen this before. In previous winters the car has been in my garage which is more substantially build than my daughters but still unheated. Here's a picture of the bootlid




Steve Church

And one of the bonnet.




Steve Church

I'm assuming this is terminal and likely to be respray time. I don't suppose anyone has any better news?
Steve Church

I've never seen anything like that! Did you have the paintwork done or was it done by the PO?

Is the paint flaking? Or is this possibly some sort of reaction on the surface of the paint?
Trevor Jessie

The paintwork was done by the PO in the early '90s. I don't think he made a particularly good job of it overall as it is a bit thin in places. Apart from some cutting back to get rid of some orange peeling the paintwork has been untouched by me. I'm wondering if the recent freezing weather (-6 C) has had an effect. funny thing is that the wings and doors are ok (at least not found any there yet).
Steve Church

Steve,

If it were a boat i'd say you had 'osmosis' - boat pox !

I've looked in a Haynes 'Car bodywork Repair Manual' and it says - Blistering
'can effect new or aged films - commonly occuring during periods of high humidity followed by sharp frost spells.

Cause - trapped moisture or air under a paint film causes blistering . Even best paint films are permeable to water vapour, moisture expands / bulds up pressure etc.

If you want i will scan at work and send you the page.

Sorry to see it - off to garage to check mine - same conditions !

Richard.
richard boobier

Thanks for that Richard. I hope you don't have the same problem after having it sprayed last year. The garage it was kept in is damper than mine. It's one of those communal block garages. Not particularly water tight and very little ventilation. I did put a tarpauline over the car though. So damp then sharp frost sounds a plausible explanation.

I've just bought an MX-5 which has usurped the Sprite's position in the garage. I was planning on making a 'perambulator garage' to house the Sprite. I'm not so sure now. Surely not everyones midgets are kept in warm dry conditions, are they?
Steve Church

Steve,

I personally think non breathing membranes over cars are worse than none - better if membrane is fixed to u/s of roof if any leaking etc.

The wifes new MX5 sits out on the drive - last night it had a very very thick layer of frost ice on it !

As i said i will scan the page and e mail off board if you want - suggests stripping back to bare metal etc.

R.
richard boobier

Thanks Richard, the thought of a bare metal respray fills me with dread. If you could scan relevant section I would appreciate it. I believe you have my email address already. I may have to revise my thoughts on where the MX5 resides. Maybe put that in the perambulator garage. Or maybe I should just get the softtop reproofed!
Steve Church

not to flame you in anny way but i think the tarpauline pushed that paint over the edge.

it always is better to keep the car free of covers as all of these will trap moist ant even atract it (condensation)

so no mather what they claim don't cover up the car
Onno Könemann

>>>>>>> I did put a tarpauline over the car though. So damp then sharp frost sounds a plausible explanation. <<<<<<<


Yepp!!! That will do it, so sorry to see it, Along time ago, MMmmmm 25 years or more I worked in a body shop and had the exact same thing come in, he had it under a tarp ...laying on the car its self for over a year, we actually picked at an edge and peeled the entire coat of paint off the panal, in one swish...talk about striping a car the fun easy way...


this is why you dont want to leave magnetic signs on cars also.

prop

Prop

Steve your bubbles are micro blisters where there is moisture trapped in the primer or a filler repair the cause of this is where the panel was not dried out before it was painted there is no solution but to repaint but providing the tops do not lift off the bubbles you may well find as the weather warms they will hopefully go down they unfortunately reappear in zero temps if i was you i would leave well alone Barry King
bp king

Barry,
Thanks for that ray of hope. I shall certainly not be doing anything until the weather inproves. It is certainly milder today (6 degrees C)so I shall be taking the Sprite out to dry any damp out and give it some TLC. I'll monitor the condition of the paint.

Hopefully feeling a little more optomistic today. Have just returned from A&E having taken the wife in with a suspected broken arm. Just badly bruised fortunately. And we were in and out within an hour (I'd taken a packed lunch just in case!). The sun is out and it's above freezing so feeling not quite so glum.
Steve Church

Classic example of moisture penetration... this happens when the paint is wet for long periods. You'll find the pimples will go when the car is dry for some days/weeks. But it will return every time the car is stored under damp conditions.

BRB has some pimples on above the rear n/s arch from a couple of winter's ago when I left it in the garare touching some tyres hanging on the wall; the garage is away from the house, and the tyre/paint joint became water-bound during a very damp spell.

It's not the end of the world!

A
Anthony Cutler

Yeah its not the "end of the world"....that dosnt happen till 2012 dec. 21 at 11:11gmt.....just so you know:)

Prop
Prop***The End in 2012

The odd thing is that only the bonnet and boot have been affected. Possibly these were sprayed off the car when it was renovated so could have had been painted in different conditions.
Steve Church

This thread was discussed between 10/01/2009 and 11/01/2009

MG Midget and Sprite Technical index

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