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MG Midget and Sprite Technical - Paint problems again

Not the first time on this topic for me, and still no end in sight. To recap, I originally sprayed the car in fleet enamel, which was a disaster. I had been severely misled by the paint supplier, but that's another story. So when I got the steel bonnet ready to paint, I reverted to cellulose which I have been spraying since 1965. The first attempt looked good, but within a year the Colorado Red was fading darker. Another paint supplier advised overcoating with UV stable clear, which is what I did. So on went another coat of red, with the clear coat going on after the base colour had hardened enough to flat. That was seven years ago. Now look at it. That long line next to the striplight reflection is one of many cracks. In several areas the colour coat has cracked underneath the clear. It did the same on the hardtop, which was sprayed more recently. The colour and clear came from the same supplier, as did the fast colour thinners. I have emailed the supplier for advice but no reply, probably locked down. There is no solution but to sand off the cracked colour coat and re-do it.

As I say, I am not exactly new to spraying cellulose, and in the old days when I was young and very foolish I took nowhere near the precautions I have to take now. The results were always good and I still have photos of the vehicles I sprayed. My first Sprite I also sprayed bright red in 1971 and I never noticed it fading over the five years I owned it. What has happened to paint these days? What could I be doing wrong?

Les



L B Rose

My understanding of red paints fading is the use more recently of non lead pigment formulations which deteriorate when exposed. My Sprite was painted in red in 1985 and hasn't faded it just needs polishing to remove traffic film which darkened it.
David Billington

That would be my guess too Dave, but the cracking is much more of a mystery. Odd that's it's not all over, just certain areas. It has done the same where I have sprayed in a patch after repairs.
L B Rose

Les,

My experience of GRP which I assume your hardtop is formed with, is that you are best going with paint specifically developed for that material.

Yacht paints for GRP both polyesters and epoxies are able to accommodate more movement/flexing etc.

There are quite a lot of manufacturers such as International, Blakes, Jotun etc - in small quantities you may struggle if you a want colour match though.

R.
richard b

Was the clear coat ready thinned? If so probably a single pack acrylic based lacquer. Although from the same supplier cellulose base and acrylic clear are often incompatible - especially if the base hasn't finished gassing out. The clear coat goes on sealing the surface, but thinners in it are re absorbed by the substrate, softening it and resulting in crazing like yours. Upper surfaces are often worst affected as they go through greater changes in temperature. You need old school lead based celly and no clearcoat.
f pollock

Yep
Looks like too much thinners soaking through to me as well, overflooding the last coat or two trying to get a wet smooth looking finish off the gun will cause it , better off dusting several light coats on and rubbing back between if you need to and plenty of drying time between coats
William Revit

Another issue can be the total depth of substrate. If you've painted from bare metal or fiberglass and have a healthy dose of filler, followed by cellulose based high build primer, and subsequent colour coats this can represent a formidable soak depth both for moisture (as they are all hygroscopic) and solvent, which even without the clear coat can take years to fully evaporate. And to be honest painting in the UK is a challenge as there are very few days when the air temp and humidity are good enough for long enough for the bodyshell to have lost its moisture prior to paint. So fast thinners are often recommended to speed up the flash time in unfavorable conditions, but many will experience problems with micro blistering or other paint issues months or even years later.
f pollock

So you don't feel too bad, here are a couple of examples where even pro body shops screw up. A mate of mine has a nice duotone ZB and 4 years ago decided to have a bare metal respray. He took it to a local place in Telford, and they put in new floors and sills, pulled the engine and all the glazing. Bodywork continued for about 6 months and it was then prepped and painted in 2 shades of grey. He was delighted - I less so as some of it looked pretty shoddy and they woudn"t warranty the work. 2 pack of course but within a year rust was breaking out. They agreed to locally rework the areas, but after another winter those areas had failed and new ones had sprung up. It wasn't that expensive, maybe 4.5K, but the whole thing needs redoing again now and of course they are refusing to even look at it.
Then 2 years ago I decided to have my lovely old Jag repainted. So it went to a well known outfit near Coventry who took 4 months to complete the work. Within 2 months the bubbles appeared where new sheet metal was supposedly stitched in, so after profuse apologies the car disappeared for a further 9 weeks. The work was completed and l was happy till the summer arrived and this time the whole of the bonnet and top of the wings erupted in micro blisters. So they took the car back again, decided to strip all the paint off, and repaint from bare metal. 17 weeks later the car was ready. Well I'd had enough so l asked them to buy the car off me - which they did, and it was eventually sold at auction.
f pollock

Thanks for comments chaps. Firstly, the hardtop is of course fibreglass but the bonnet is steel. I don't think the substrate is very relevant, as they both show the same problems.

The colour and clear coats were not pre-thinned, and were labelled as cellulose. I used fast thinner which they supplied. Having had paint mis-described before, I wonder what it really was.

I have long since given up with getting a perfect finish straight from the gun, although that was easy in the old days. I resign myself to flatting and polishing after at least a week and usually much longer. Hence I don't flood with thin final coats.

Yes I had micro-blistering with the first colour coat which faded so badly. Another reason to re-do it.

Don't tell me about crappy professional paint shops. About 10 years ago accident damage to the rear end meant a lot of panel beating and respraying in 2-pack, paid for by the insurance. The existing finish was the fleet enamel, which I was quite pleased to get rid of. Also I had left the shell in primer for too long and there was a lot of blistering. I paid the paint shop extra to strip to bare metal, which of course they didn't and blistering reappeared after about 2 months. They did it again free of charge, but several years later I had to re-do the wing beading and what did I find? My chromate primer of course, which they still hadn't removed. There are still blisters under the 2-pack, which I promise myself to sort out one day, if I live long enough.

I really don't know the answer. Professionals are expensive and unreliable, paint for amateur use is mostly rubbish. I am right now doing various touchup jobs. I airbrushed a bit of the driver's door (which is off the car, laid flat), and the colour coat went on OK. After waiting for it to harden, I flatted and sprayed on the clear coat. Damn it if I didn't get a run - hardly ever happened in the 1970s. Flatted off the run, tried again. The weather has changed and the clear coat bloomed. In the old days it had to be tipping down with rain for that to happen.

Before anyone says "he obviously doesn't know what he is doing", here is the scooter I sprayed with cellulose in 1966, photographed when I sold it 2 years later. And here is my first Sprite sprayed in red cellulose in 1971.

Les






L B Rose

I can add that the maroon paint on the scooter was 10 years old when I used it! I found it in my dad's garage - he had used it to spray his car in 1956, using a gun he made out of bits of brass. I can't remember where the silver came from, we never had a silver car.

Come to think of it, the white on the scooter was also 10 years old - the Hillman was 2-tone, very bold in those days.

Les
L B Rose

Les
I'm wondering if it might be a combination of the paint itself, drying time and heat
I won't name products here----just in case-
A hotrod builder I know 'always' used a well known American paint without fail, nothing else was good enough in his eyes, which he had a fantastic run with but was talked into changing to another brand which was also a very well known company
He had heaps of trouble with humidity blisters and cracking like yours
The paint rep. visited him and said the paint he was using was designed for using in a controlled environment (read oven) and if he was using it as normal with just heat lamps he would have to double his drying time between coats otherwise the thinners from the next coat will get down through the not quite dry coat and into the primer and the whole paintjob won't dry off properly for months as the air can't get to where it's supposed to get to--It dries eventually but shrinks back causing long cracks on the surface that go right down through the job
Not for a second would I suggest you don't know how to paint, I'm thinking you've got caught out by the product, It'd be interesting to get the rep from whatever brand paint you used to have a look and give his/her opinion
willy
That maroon on the scooter looks the business, I painted my old 100/4 Healey very similar to that a very long time ago--ahh the memories-thanks
William Revit

It does seem as if the laquer has sealed in the cellulose colour coat too soon, thus not allowing it to release all the solvents. I have limited experience of using Jawel's cellulose high build primer and colour coat (BRG) in the last few years - still have more external panels to paint. Anyway, what I've put on is fine so far. I sprayed the primer one day (2 or 3 coats)and the colour coats the next day or two. As I understand it, you can spray several coats of celly with very brief drying intervals, say 15/20 minutes on a warm day (premium thinners for colour coats).

Les, you have far more experience than I but I was just commenting on my experience with one brand of "modern" cellulose.
Bill Bretherton

Next time you are ready to paint you may find it helpful to check out the 5 day weather forecast for your area. For cellulose its usually recommended to be at 15 degrees minimum - 20 ideal and 55% or less humidity. I try to stick to that and keep a temperature/humidity meter handy to double check.
f pollock

Thanks, yes, I'm generally aware of temperature and humidity requirements although, apart from the last few exceptional weeks it's often diffcult to get a run of decent days when you happen to be ready to paint.
Bill Bretherton

I just got a reply from the supplier. The paint was from PPG, who sent me this link:

https://uk.ppgrefinish.com/en/paint-defects/cracking/

Nothing new to me there, and I have already followed all those precautions. They still don't say why fading and cracking are such a problem now, but not decades ago.

Les
L B Rose

I just had a useful chat with the paint supplier Simply Coatings. They said that they no longer recommend overcoating with clear as the latter dries faster and causes solvent trapping in the colour coat. So what do I do about fading I asked? Use a different brand of colour coat they said, and they will send me a sample. I said we will have to wait a year to see if it fades, and fours years to see if it cracks.

As you might have seen from another thread, I am refurbishing the hardtop. I have flatted off all the cracked paint, and found that even after this there was a patch of red that had not hardened. It's three years since the last respray. So I scraped off the soft stuff and will try the new brand of paint on the whole unit. The new brand is HMG and the old one was PPG. If I am not overcoating then I will be able to see if it hardens quickly.

The nice man at Simply Coatings basically says that there is no real solution other than 2k. The days of amateur car painting are coming to an end.

Les
L B Rose

Les, Jawel paints sell a 2K system using non-isocyanate hardener. Not suggesting this is a way for you at the moment as you have already selected your materials. But it may be a useful alternative for DIY spraying. I havent heard any reviews or experience quoted for it yet.
GuyW

Just take your time, thin coats and plenty of drying time between
William Revit

I suggest this as an alternative. Refinishing the top again using yet another supplier has no guarantee of success. So what if it could be dropped off, refinished in 2K and carry a real world guarantee?
Chips Away have painted on site and from bare metal my 1979 GTB in its original argento silver and I'm happy with the result.
There will be a center near you in Wiltshire. Why not take the top along for an appraisal and see what they are prepared to offer you. Or try the one I used one in Telford - I can give you a contact.
f pollock

Thanks for the tip about Chips Away. The local chap is 10 minutes away and he just came to look at the hardtop. He says he will do it in water-based for £240. I am rather surprised than he can do this in my garage. I thought certain facilities were needed for water-based paint, such as forced air drying. What about dust?

Les
L B Rose

I suppose I'd take the view that Chipsaway do thousands of successful repairs on location so they must have a process that works. Having said that it seems obvious that repairs done in a designated body shop with a state of the art paint booth, where every aspect of the repair can be finely controlled would seem to be a better bet. Chipsaway is a franchise so some are a one man band operating out of a van, and others have extensive paint facilities and often the local repairers for the likes of Porsche and Aston Martin. The place I took the Ferrari to has both premises and a van and regularly do the high end and older stuff too. If you were to choose one with a body shop and you were pleased with how the hardtop turned out,you might consider the same people repaint the rest of the car. You need to interrogate any special terms on the warranty.If on the hardtop he is offering you the strapline ChipsAway Lifetime Ownership Repair Guarantee this price might seem too good to pass up.
f pollock

GuyW said:

"Jawel paints sell a 2K system using non-isocyanate hardener. Not suggesting this is a way for you at the moment as you have already selected your materials. But it may be a useful alternative for DIY spraying. I haven't heard any reviews or experience quoted for it yet."

I used this last year to paint a Bongo. I found it very easy to work with. Once I got the spray gun set up to give a good wet(ish) fan the finish was quite good direct from the gun.

I think I will use it again when I do the V8 but I'm using celly for the B currently at the painting stage.

Best of....
MGmike

M McAndrew

I'm about to try some HMG cellulose just arrived from Simply Coatings. I'm now confused by BMC paint codes. It seems that RD2 is two different colours, Colorado Red 3742 and Signal Red 6200. I think they have sent 6200 as it looks different.

Les
L B Rose

They now say that Colorado is RD1, but their chart shows Signal is also RD1! They are definitely different colours.

Les
L B Rose

Today I had another very long chat with Ken Burdekin. My goodness he likes to talk! I think that bit by bit I have to remove all the problem paint and use the right stuff. He thinks the main problem is thinner, which doesn't flash off properly because most of it these days is recycled. I have been very unlucky in choice of colour. The car came to me in Colorado in 1978 and Ken thinks that it would have been the ICI product in those days. Long since gone from the market. Nobody has been able to reproduce the colour exactly since then as one of the tints was exclusive to ICI. I liked the colour so kept it, but maybe should not have. Bright colours like this were much more expensive in the 1950s, hence only for Big Healeys and export markets. Dull boring colours were kept for UK Sprites.

I can't use the sample of HMG colour as it's wrong - Signal not Colorado. I will have to send Ken a sample of what's on the car and he will try to match by eye. I will then re-do the hardtop to see how I get on, and if it's good I'll go over the car panel by panel.

Les
L B Rose

I bit the bullet and bought the HMG Gipgloss from Ken Burdekin, matched to the sample I sent. Yesterday I tried it on the headlamp shells that I had prepared, and the match is perfect. I also bought 2k etch primer and high-build primer, both non-isocyanate, as Ken recommended. The etch is of course for when I sand off the old paint and go through to the metal, the high-build is to go on fully hardened and sound old paint. It will help to prevent frying up when the colour goes on, a constant problem I have had. I'll try to do this without paint stripper, as that will affect body filler. Wish me luck!

Les
L B Rose

It never rains but...... The pressure switch on the compressor has failed, so no spraying for me. Does anyone know the size and thread for the air tank outlet on a SIP Airmate 21525 (horizontal)? No good asking SIP, they know nothing and are wanting nearly £80 for a new switch and regulator. I can get a generic one for a tenner on eBay but no sellers there have any idea of what size their inlets are. That's if they are not a robot of course.

The spigot appears to be 15mm but I can't identify the thread - is it metric?

Les
L B Rose

OK, I have worked out that it's 3/8" BSP. Correct?

Les
L B Rose

I know you are all on tenterhooks for the next episode in this saga. I bought one of the cheap Chinese switch/regulator units from eBay, but the connection to the air tank is the wrong size as I expected. Fortunately they have copied the SIP unit quite slavishly and I was able to remove the base casting from the old one and install it in the new one. All works perfectly. Hardtop sprayed - not too bad but will need compounding.

Les
L B Rose

This thread was discussed between 01/06/2020 and 01/09/2020

MG Midget and Sprite Technical index

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