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MG Midget and Sprite Technical - Comprehensive Paint Systems

I am after information so I can prepare ahead for painting my Frog. Over a considerably extended period of time I have carried out almost all of the welding repairs needed on the tub which is now a mix of new panels, repaired panels and areas which are solid but have surface rust. I have arranged to get the whole thing media blasted so it will be down to bare, bright metal.

So I need to be ready prepared to get a first protective coating sprayed over the whole thing immediately, and before any micro-rust begins to develop. I presume the best for this first coat would be an etching primer of some sort, Currently thinking of using Bilt Hamber Etchweld but there may be something better out there?

Once that is on I need to weld on the rear "clip" which is why I would use this weldable etch primer. After that I am not sure what product is best. Maybe a further layer of anti-corrosion zinc primer or Bonda Primer (which is what Lawrence would praise highly). But ordinary primers are not waterproof and it seems to me that some sort of polyurethane primer might be better? There is a product called Epoxy Mastic 121 which makes high claims. http://tinyurl.com/zezd2rh

After that it will be normal prep with coats of high build primer and lots of flatting! I will use stone chip for the undersides. For final top coats I favour cellulose over 2K. I have tried both, and yes I do have access to facilities for spraying 2K safely, but I found celly much easier to get the finish that I wanted.

Any views of a comprehensive paint system of products that work well both individually and also together.

GuyW

Guy,
You have obviously given this some serious thought and have firm views with regard to 2-pack/cellulose, but I'm going to share my views here anyway :-)
1) It's a frogeye. Any money that you spend on getting a top quality finish will be money well spent if only from an investment point of view. (Not that I'm suggesting that making a profit is your motivation)
2) A good professional will know exactly what combination of paint systems will work well together.
3) Don't dismiss 2-pack as a solution. It's incredibly durable, doesn't suffer from some of the shrinkage / settlement issues that can occur with cellulose painted cars (even those done professionally). My frogeye was painted in 2-pack back in 1989 and it's bright red. The finish is as good today as when it was newly painted. I have recently had my Elan professionally painted in 2-pack - £3k very well spent IMO.
Just my tuppence worth
Simon
Simon Wood

Guy,
Another thing regarding Bonda-Primer. Like Lawrence, I too am a fan of this stuff but you need to be careful if you want to put a good finish over the top as in my experience it doesn't cure as such it merely dries out. Put something cellulose based over the top of it and it will all go horribly wrinkly and you'll need to start again and seal it properly.
Simon
Simon Wood

Thanks Simon, just the sort of information I was wanting on paint systems compatability.

Re the celly v 2K issue. I have sprayed both, and got good finishes with both. The difference was the Sprite that I did with celly in 1992, lasted a good 20 years of heavy daily use. When it did get the odd damage it was easy for me to blow in a part and blend it to the rest of the body. I then re-did the same car in 2K and it hasn't lasted anywhere near as well. 4 years on and there are cracks and sinks in the surface and other areas have just lost the sheen from the paint film. I have sprayed 2K myself, but just on small panels. The Sprite was done on that occasion by a professional.

I haven't decided yet if I will paint the Frog myself, or take it to get it done. The place I would take it this time (different from the last bloke!) specialise in restorations and would do either celly or 2K, whichever I choose.

But that is jumping ahead. I really need to know what combination of primers to use first. I will try asking the paint shop what they recommend, but thought I would explore what others have done here first. I know there are knowledgeable people around regarding paints here. Cue: Bernie?
GuyW

Guy, surely you need to decide whether the top coat is to be celly or 2K, *then* find out which primers are compatible, not the other way around?
David Smith

Guy,
It's interesting to read of your bad experience with 2K. I had always been led to believe that properly applied/baked/cured 2K is very stable and shouldn't shrink - it effectively becomes a plastic skin. A couple of months after my Elan was done, a large crack appeared in the paint on the bootlid. The painters that did the work rectified this and put the blame on the primer sinking slightly into the fibreglass. They claimed it was the primer not the finish that was the problem. Fibreglass has considerably different painting requirements to steel but mine was primed / baked and then top-coated / baked. All a bit long-winded and nigh on impossible to diy.

Having been unashamedly waving the 2K flag, I would be the first to admit that a well finished cellulose-painted frog in an original colour is an object of beauty. I suppose that it all comes down to what you are trying to achieve.
Simon
Simon Wood

The "Celly" paint that is being produced today is not in fact Celly, but Acrylic which is compatible with Celly thinners and is mixed the same, ie 50/50.
As a rule of thumb, don't mix the two systems.If you want a 2k top coat, use 2k primer. Don't use any Celly based products. (Simon mentions the possible problems of Bondaprimer and Celly). I've never used Bondaprimer, so I don't know.
There are also different quality 2ks. Lechler is excellent, as is Prospray, but there are cheaper versions which are not as good. I did my Sprite in 2007 in Mipa 2k from bare metal and it is still very shiny with just a few stone chips around the front of the car after 9 years and 17,000 miles.

I was speaking to a friend who is a professional, the other day, and he mentioned the very problem that Guy refers to, 2k put on top of old Celly. He said the new 2k will eventually cause the Celly to move under it causing cracks. I didn't know that, but he works on moderns, classics, does insurance work etc and uses all different types of paint systems, including water based, which he doesn't like. I will be seeing him tomorrow, so I will ask him why it happens. Maybe it's something to do with different thermal expansion of the two systems, but that's just a guess.
A MASC N.West member has had all kinds of problems with his Frogeye with sinkage, cracking and the paint not drying properly and actually falling off. I think there is more than one cause though. Too much paint already on the car and not enough binders in the paint when it was mixed.
Bernie Higginson

Its clearly a real minefield! Which is why I am trying to learn from other's experience not just my own.

David my in-decision at this stage is whether to paint it myself or get it done professionally. I wouldn't use the same person as last time as I have suspicions that the problems arose as much from his methods as from possibly incompatibility with underlying paints. The paint he used was U-pol and I remember thinking it was very thin. He did use a primer over the celly that I had put on 20 years earlier, plus over bare steel and over filler. Not sure what that primer was other than it too was a 2K product.

Anyway, this time, with the Frog, it will be starting from bright steel so, as long as I go for a "Comprehensive paint system" (as in the title) I shouldn't get any problems.

What I am after is advice of what goes together well, for example, if using Celly (Acrylic)finish then use products a, b and c for prep coats, but if using 2K finish then use products a, d and e. Maybe life just isn't that simple!
GuyW

OK understood; from bare metal is good!
are you buying the paint mail-order or do you have a local supplier? If the latter then I'd definitely ask them too.
David Smith

Hadn't decided that David, but no harm at all in discussing with local paint suppliers. Small family firm, they have been helpful in the past on (non-car related) paints. Good idea!
GuyW

Both my Frog & Elan were painted with MaxMeyer 2K. Paint on Elan was only painted 18 months or so ago and is considerably thinner than that applied to the Frog in 1989.
Simon
Simon Wood

I spoke to my professional painter friend today and he explained the problem of applying 2K over old Cellulose.

He said: If you take a car which has been painted in Celly, no matter how old the paint is, and wipe a thinners soaked rag across it, you will get paint on the rag, because the solvent is attacking the paint. You will get the same effect when applying 2K on old Celly . ie., the solvent in the 2K thinners softens the Celly. Now, Celly, being an air dry paint, takes longer to dry than 2K because the hardener in 2K creates a chemical reaction and dries quickly and blocks out the air from the freshly softened Celly, so the Celly never fully "re-cures", and even though you have a perfect 2K finish, the Celly beneath it is still in a semi cured state, which can lead to loss of adhesion, particularly on reverse angles like swage lines. It may take quite a time, but it will happen.
From bare metal he recommends 2K etch primer (etch primer with an activator rather than aerosol etch), followed by 2K high build primer, then 2K top coat. 2K primer is not as susceptible to moisture absorption as ordinary primer, but the best method is to do what you need to do as soon as possible after removal,of the old finish.

I hope this helps. My knowledge is limited to being a non-time served general mechanical and body repairer, but I do have access to very knowledgeable professional friends in the trade and I'm always asking questions and learning as I go along.
Bernie Higginson

Bernie that's interesting - and helpful.

The story on my Teal Blue '71 Sprite is that in the early 1990's I did a major reconstruction from a heavily rusted shell. Very much as I have been doing on my '60 Frog. Having completed the welding, I then grit blasted the whole thing using a heavy road compressor and pot blaster, borrowed at that time from a friend who had a plant hire firm. It was a pretty brutal bit of kit, but I turned the pressure down and only directed the blast at a low angle across body panels to avoid any distortion. Having blasted it to bright shiny steel I sprayed an etching primer on immediately. That's all a bit of an aside to the tale. I resprayed the car using celly and was pretty pleased with the results.

Forward to 2010 and it was due a respray. I did all the prep and got a professional to top coat with 2K. Most of the surface was in well flatted celly. I remember asking Fred if it needed some sort of isolating coat before the 2K primer. He answered no, because of the age of the celly all solvents would have long since evaporated off. The respray looked good when first done (see photo) but 5 years on it is looking tired and shabby. So that is one problem I need to deal with.

At the same time I am nearing the first paint stages of the Frog. But that at least will be from bright steel and not suffer the problems of overspraying an existing celly paint system.


GuyW

Guy. Yes, I remember you posting that picture at that time and my remarking what a great finish you had achieved.
BTW. I love those wheels, they look a bit wider than standard, what are they?

I forgot to add in my previous post that baking in an oven is much better than letting 2K air dry. It cures much harder.
Bernie Higginson

Precisely what I was about to observe, my dear fellow.

What are they?
Nick and Cherry Scoop

Cosmics,
Very rare in that pattern/size. 13 X 5.5J

Fred, the professional painter, did the edges, one side and the bonnet and then let me do the other side rear wings, doors and boot.
I recon I got as good a finish as he did, and the bits he did havn't lasted any better than the bits I did!
GuyW

Guy, when I stripped my shell back to bare metal a few years ago I had the same problem regarding stopping rust while getting ready for paint. So I used the same technique I use for my motorbikes over winter, a 1 to 4 mix of oil to white spirit in a garden spray bottle and then just spray everything with it. It leaves a nice oily film over all the bare metal, mine stayed like that for months.

When it came time to paint it I just degreased it with pre paint and then gave it a coat of etch primer. Next was a few coats of high build primer and then about 4 or 5 coats of celly.
john payne

Thanks John,
Can you remember what brand of Etch primer you used? Was it critical to match it to the celly paint you used for the top coats?

The oil spray is a good idea. But I am a bit beyond that stage. What I have been doing is doing the welding repairs and then giving each part a coat of paint from surplus paint colour rattle cans just to seal out the rust. This will all get stripped off when I get the blasting done.
GuyW

I'll try and remember to have a look tomorrow Guy, I think I've still got the tin. It was from Auto Paints St Helens and it seemed to do a decent job, I might even have some photos of each stage somewhere. I used an isolator primer for the engine bay as there were still areas that I couldn't quite strip to bare metal but the rest of the body was just etch, primer then celly.
john payne

Just had a look and they no longer seem to do the etch primer at St Helens, at least not one I recognise. On the site I used for advice on painting it seems they don't use it much anymore:

http://www.mig-welding.co.uk/primer.htm


john payne

John. That link is an excellent reference point for all aspects of body repairs. It's been around for a long time, but it is constantly updated as new materials become available. I would recommend it for people who are doing their first restoration and also those who are more experienced.
Bernie Higginson

Yes its an excellent site - I have used it a lot for welding advice. Never thought about checking in on their paint pages though. - Something to do with the title?

Modern cars protect the steel with phosphate, zinc and other treatments. - And you rarely see a rusty car on the roads, compared with 25 years ago when anything more than 4 or 5 years old had a frilly rusted fringe to wheel arches and doors. Has no one got experience of enriched primers of this sort?

I think Neil, from Pembrokeshire had some helpful experience from his restoration projects. But he got lured away by the K-series gang who fled to a facefat web place somewhere.
GuyW

I'm surprised no one is mentioning controlling surface temperature and humidity, as these are key factors affecting finish and durability - especially when starting from bare metal.
But I think the first question to ask - if you elect to take the car to a professional painter and pay good money,you need to ask for a guarantee.A guarantee that there will be no paint related issues for a reasonable period of time - say 3 to 5 years.Or it will be rectified at their expense.And then ask them what prep work would they allow you to do. Knowing that temperature and humidity aside from the minefield of compatible paint systems are all fundamental to them achieving a long lasting and flawless paint finish,I think they will demand to do the whole lot from start to finish.Unless you're able to force dry the shell before and after the prep stage you'll likely end up with micro blistering in the top coat, that the professional paint shop will have no control over and can't guarantee against.So looking at the wording in the small print would be my first call, and fixing a cast iron guarantee will determine how much or how little you do - and with what.

Fergus

Thanks Fergus.

The paint shop don't do bare metal stripping, so I need to go somewhere else for that. The person who does the stripping doesn't do painting. But as I believe it is vital to get a first etch primer coat on within minutes of blasting, he is happy for me to go and do that at his premises, using my own equipment. Once it is in this state it then needs to come back to me for fitting the rear bodywork and tidying up in preparation for its second outing to the paint shop. So I want to either use an etching primer that seals from atmospheric humidity, or apply a second coat of something else that does.
GuyW

Whenever anyone starts a thread about paint it runs and runs! Well hopefully the paint doesn't, just the thread. Anyway please forgive my rabbiting on, which will be more about what not to do - from bitter experience.

I have sprayed celly on and off since 1965. In the old days there was a paint factory in Croydon (a block away from where I was born actually), B Selier & Co they were called. I used to go in there and get any colour I liked mixed cheaply, and it was good stuff. My dad sprayed his cars with their paint (he made his spray gun and compressor but that's another story), and I followed the family tradition. Being young and stupid (and broke) I never bothered with expensive materials and only used bog standard thinners, yet got excellent results. My A35 was Aston Martin metallic green and my Mini was eye-watering orange. For my first Frogeye in 1971 I bought a gallon of Post Office red celly (not from Seliers as they had closed by then), and it still looked good when I sold the car 5 years later.

But I'm convinced that it's much harder to get good quality celly these days. I restored my steel bonnet a few years ago, well very few as it only went back on the car in 2013. I etch primed the bare steel, and sprayed 3 coats of high build grey. There followed a few weeks of flatting and stopping with guide coats, allowing ample time for everything to harden. I bought celly mixed to pattern from Rainbow Paints in Dorset, and it looked pretty good when it went back on the car. It's now much darker than the rest, and has sunk so badly that many scratch marks in the body filler are visible. Yes there is filler as the welding was extensive! So I have to do it again.

This time I will put a coat of clear lacquer on the Colorado Red. The colour comes from Simply Coatings and they say the clear lacquer has some UV protection. This darkening problem has affected other panels repaired in recent years and I am re-doing them with new colour and lacquer. I find the lacquer a lot harder to flat and polish, which is encouraging.

The rear of the car is however in 2-pack, because of an accident several years ago. It wasn't a good job. As I had some rust bubbles (because the car sat in primer too long during the rebuild) I asked the body shop to strip the paint to bare metal before respraying (I paid extra for that). Within weeks the bubbles came back, so they had to re-do it. Now, some 6 years later there is more bubbling. The advice to get a guarantee is good, but when it's an insurance job that may be hard to get. And the 2-pack also darkens, although more slowly than the celly. Interestingly I had the same rust issue on the doors and treated them with Kurust on top of the primer. No bubbling after 15 years!

So what's my advice after all this? The great beauty of celly is ease of repair, and if you keep the car for years you will inevitably need to do that from time to time. I am obviously wary of body shops, and generally I prefer to be in control. A final word of warning. When I rebuilt the car I asked the paint supplier (a different one) for 1k acrylic. They sent polyurethane enamel. I said 'no you have got this wrong'. They said 'oh it's just the translation, it'll go on lovely' (the paint was Italian). It was a disaster - horribly slow to dry and ran all over the place. Not particularly durable either. If you are tempted, don't.

BTW has anyone used clay blocks for flatting?
L B Rose

Interesting - to me at last as much of what you say about celly matches my experience. But I think he problem isn't with the celly coats , but with what goes on before them.

Most primers are not waterproof so your comment about the rear of the car "I had some rust bubbles (because the car sat in primer too long during the rebuild)" is what I would expect. Especially if you also wet sand the primer coats. The water goes through the primer and reacts with the steel.

I believe the solution is a waterproof first priming coat, after the etch primer and before any high build coat. This would isolate the steel from either water from wet flatting, and even from just atmospheric moisture which will permeate through a normal high build primer. The reason that paint shops don't need to do this is because of the controlled environment that they work in - low humidity, heated, and quickly progressing through the work.

What I don't know is whether the zinc rich primers available would be an alternative approach sufficient to counteract any moisture penetration during that vulnerable period before the (waterproofing) top coats are applied.
GuyW

Well Guy, zinc rich primer didn't work for me - I put some on the rear end over the chromate primer. But Kurust did work.
L B Rose

This thread was discussed between 21/03/2016 and 27/03/2016

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