Paintwork tips

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Paintwork tips

Postby Paul Dawson » Fri Jan 10, 2014 9:21 am

I've just obtained a litre of Henley Blue cellulose from our local paintshop. My Viva's paintwork is about 70% original though obviously showing a fair bit of 'patina'. Rather than send it to a bodyshop for a full respray I want to try to do running repairs to the bits that need it most.

Most of the exterior isn't too bad. A good polish will get most of the colour back.

The problem areas are the rear o/s wheelarch which has been replaced. The whole panel below the stripe is now in grey primer.
Image

The sills - which have had a small welding repair at the back end. The rest of the sill is solid, but the chap who did the welding sprayed the whole sill with a rubberised anti-chip product. I've had to take them back to bare metal.
Image

Front panel needs a tidying
Image

I know I won't get a showroom finish - that's not what I'm after. I just want a reasonably tidy old car that's solid.

I don't have a huge garage with a compressor and spray gun. I have a single garage and an airbrush with a small compressor. I've used it for model aircraft with 6 foot wings and got half decent results, so I'm planning on doing small areas at a time.

I know it's no good doing anything whilst the weather is so cold. The garage isn't heated and from experience even putting a couple of fan heaters in there doesn't do much. So I'm going to have to wait until the weather warms up a bit. So in the meantime - any advice or tips on how to get the best finish possible with the very limited resources and skills at my disposal.

Just for information. I have a litre of cellulose primer (grey) and topcoat (Henley Blue mixed to the code 3BL). 5 litres of good quality anti-bloom cellulose thinners. 2.5 litres of Bonda Rust Primer. Acid-etch primer in a rattle can. All the bare metal has been treated with Dinitrol Converust.

Thanks

Paul.
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Re: Paintwork tips

Postby 1972nail » Fri Jan 10, 2014 6:05 pm

A good finish is 100% dependant on good preparation. You've got the correct materials you just need to apply them properly.

I suggest putting on the etch and a couple of coats of Bonda Primer ASAP and let it cure and more importantly sink for a week or two. No rubbing back yet! Then build up a few light coats of primer and again let it 'sink' a bit. Then a light rub back with 600 wet and dry, used dry, or a red 'Scotch' pad, to check for nibs, dust etc.

Another coat of primer and a very light dust of cheap mat black, or intact any old rattly can you have left over, as a guide coat.

This is where the fun begins.....

You need to carefully and slowly rub all of the guide coat off using 800 to 1000 wet and dry used wet. You must use a rubbing block to keep everything flat and level. For large flat areas you can make a very effective rubbing block from a block of wood with an old rubber mouse mat glued on as an intermediate pad.

Any imperfections will show up as areas where the guide coat remains or the primer is rubbed thin and the Bonda starts to show through. If this happens STOP and touch up with a couple of coats of primer and another guide coat and rub again.....

The most likely areas of irregularity are where there are edges between old paint and bare metal. You should try and flat these back as much as possible before etching.

Only when you are happy with the primer should you apply the gloss.

Have fun!
Last edited by 1972nail on Fri Jan 10, 2014 7:03 pm, edited 1 time in total.
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Re: Paintwork tips

Postby Paul Dawson » Fri Jan 10, 2014 6:40 pm

Thanks David

An old mate of mine from years ago used to run a bodyshop and he always said the finish is always in the preparation. But I had no idea of the process involved. That's a pretty clear outline of how to go about it. I get on with it as soon as it's a bit warmer in the garage.

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Re: Paintwork tips

Postby 1972nail » Fri Jan 10, 2014 7:24 pm

Remember cellulose 'sinks' as the solvents evaporate off, so what looks smooth just after spraying will sink back over a day or two and show up lots of imperfections. That's why I say take your time.

Cellulose also tends to be very 'strong' in it's solvent power and will tend to 'swell' the edges is the existing paint, sometimes causing wrinkling and lifting. If this happens professionals, who want to work quickly, always use a barrier / sealer coat of some sorts. Us DIY sorts however have a bit of time to wait and can let it sink back and solidify again before proceeding.

If the edges wrinkle a bit, and they probably will on old Vauxhall undercoats, let it cure a few days and rub back the wrinkles gently before adding very light and 'dry' coats of primer to build it up again.

Never put a wet coat on a wet coat with cellulose especially over old paint, all you are doing is increasing the solvent power of the cellulose on the existing paint and you get more swelling and risk of wrinkling and therefore more sinking as it dries.
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Re: Paintwork tips

Postby Paul Dawson » Sat Mar 08, 2014 11:30 pm

As above - re. the fact that cellulose paint remains 'active' permanently and can be affected by new paint --- I've been thinning my primer a bit less than 50/50, but reading around it seems the general advice is to thin 50/50 and then for the topcoat thin even more. I've read of guys going 60/40, 70/30 even 90/10 (thinners/paint) for the final coat.

I am bit worried this amount of thinners is going to cause the paint to wrinkle. Is that likely? If it does wrinkle then if I've read the above right the trick is to leave it alone for a good while to fully harden off, then rub down, then lightly spray another coat of primer and repeat slowly allowing thin coats to build up. Does that mean that when I come to spray the topcoat on the several thin layers of primer will protect it from wrinkling again?
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Re: Paintwork tips

Postby 1972nail » Sun Mar 09, 2014 1:09 am

Paul, always allow the paint to 'flash off' as the say, become touch dry is more correct, when spraying cellulose. 50/50 is OK and 60/40 for top coats to help the paint flow and sort of melt together. Never paint wet on wet with cellulose, that will only give you trouble and keep your primer coats light and allow to dry fully until you build up a bit of thickness of new paint. The new paint will absorb the solvents from heavier top coats better than the older paint below.
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Re: Paintwork tips

Postby Paul Dawson » Sun Mar 09, 2014 9:35 am

Thanks David - this is all new to me. I prefer mucking about with spanners. I shall let you know how it goes. I think I'll stick to just working on the front panel at first, the lower section has a textured finish anyway and the smooth bit is behind the grill so if I muck it up it isn't going to show as much.
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