Tuesday, 19 June 2007

Thoughts About Paint

Car paint is pretty tough stuff and readily stands up to the range of temperatures and humidities thrown at it by our British weather. The reason that paintwork needs maintenance is because it gets chipped, scratched, and defecated upon by birds (which, if you judge by the effects of their excrement, live on a diet of battery acid and paint strippper). Thus we need to repair damaged paintwork before rust takes a hold on the metal beneath.

Maintaining paintwork would be easy if we were happy to just rub off (note that any wax and dirt should be removed BEFORE you start with the abrasives) the damaged paint, and any rust, and blob on a couple of coats of paint. So why the hell are we so hung up on the idea that a car has to have a super-smooth, high-gloss, paint job that's a really pain in the ass to achieve and even harder to repair? Metallics are even more difficult to patch up, and even more popular!

Of course this is really good for the manufacturers because it means that most people simply won't bother, the car will rot, and the owner will be back to buy a shiny new one a heck of a lot sooner than if maintenance of old one had been easier. Given that maintainability is my number one priority with the ol' bug I'm determined not to go down that route. On the other hand, the rat look isn't to my taste either so I needed an alternative solution. Thus I began to consider things like camouflage and other patterns that would allow me to divide the surface a the car into smaller areas.

To be honest, the Beetle isn't that difficult to divide into small areas. All four wings can be unbolted. Hood, decklid and doors can all be removed or treated seperately. However, as I don't have a garage or suitable shed in which to paint panels and will have to work outside, dealing with areas of this size would still be very difficult. It's also the case that no matter how hard you try to match them, newly painted panels tend to look different to the others.

Having considered lot's of different patterns I've decided upon a cubist inspired (check out Picasso's analytical cubist works) pattern of rectangles and shapes in shades of pinky blue. Here's a mock up that I did on the computer:

I intend to apply the paint with a brush because it will be easier to get the effect that I want and using a variety of shades means that I won't be tied to any particular colour that may prove difficult and/or expensive to obtain at a later date.

Note that the patterns will not hide the shape of the car as much as they do in the mock-up because they'll be following the curves of the surface. I'll also be doing the painting a bit at a time, so the pattern will gradually spread accross the car, rather than trying to do it all at one.

Having come up with a plan for the outside/top of the car, I also needed a plan for the rest and in fact it's the other areas that are more prone to rust. While water runs off the exterior of the car it can get into cavities and get's held onto the underside of the car in a mud poultice. When rust does begin to form, the porous nature of the rust means that it holds moisture thus furthering to rot. Clearly this is something I want to prevent.

Weld-Thru Primer

The first thing I've done is to buy a can of Weld-Thru Zinc Rich Primer Aerosol from Frost and I'll be applying this to all cleaned up metal that I intend to weld.


The next thing is that I've bought tins of smooth black and smooth silver Hammerite paint for use on underbody areas including wheel arches and steering/suspension components. I'll may also be use some other colours under and inside the car before I install carpet and such.

Now I've heard a lot of criticism of Hammerite but it strikes me that most of the problems are caused because people don't use it correctly. Many years ago I used it on with a wrought iron gate and was disappointed to find that the gate started to rust again a couple of months later. It was only afterwards that I realised just how many mistakes I'd made:

Firstly, I cleaned the loose rust off the workpiece. But more than that, I'd cleaned it back to bright shiny metal. I had failed to realised that Hammerite paint is designed to bond to rust. If you're painting bright shiny metal, you should be be using Hammerite Anti-Rust Primer and not the 'normal' Hammerite paint.

Then I shook the tin. This was also a mistake because it introduces air which takes a long time to come out of something as thick as Hammerite. Hammerite, unlike Mr Bond's martinis, should be stirred and NOT shaken.

Then I set about painting by dipping my brush into the tin. Wrong again as this will contaminate the paint in the can as you move the brush from workpiece to can. What you should do is to pour the paint you intend to use into another container and if there is any left over it should be discarded and NOT returned to the tin.

Then I left it to dry overnight and applied a second coat the following day. It seems I really was determined to screw this up because, for it to do it's job, you MUST apply a second coat of Hammerite within four hours of the first such that it does all the chemical bond stuff that it needs to do in order to work. Leave it for more than four hours you're just wasting your time because the second coat won't 'react' with the first coat.

As I say, I've seen a lot of criticism of Hammerite, and the critics generally advocate alternative products that are harder to find and are generally somewhat more expensive. Having done a bit of research, I'm inclined to believe that the main reason that people have any more success with these 'more exotic' products is that they read the instructions and follow them whereas they assume they can use Hammerite like ordinary paint. Hammerite is NOT like ordinary paint and if you treat as such, you will fail to achieve the desired result.

Note that I've chosen to go for the smooth finished stuff (as opposed to the hammered effect) because I want to be able to inspect it for damage on a regular basis and it'll be easier to spot stone chips and the like on a smooth finish.


While Hammerite should protect the areas where I can apply it with a brush, spraying it into cavities seems a bit hit and miss. On the other hand, products like Waxoyl and Dinitrol are designed for the purpose. These products can also be use to apply a waxy coating the underside of the car.

Bitumen based products are another option for 'undersealing' however the are frowned upon in car restoration circles. In this case I am inclined to agree as it seems that the problem with the bitument based products is that they tend to harden with age and that when they get damaged, water gets behind them, and the metal rots away out of sight behind the coating. Of course the only way to check for this would be by scraping the stuff off, and of course removing something to see whether it's still doing it's job properly is undesireable.

It strikes me that the same is true for the wax based products, many of which are brown or black. How are you supposed to tell if that uneven black/brown surface is still doing it's job or hiding rot? Thus my plan is not to use underbody seal but to paint these areas with Hammerite which I can then inspect and maintain. It has been suggested that I could use 'clear' Waxoyl however I am told that this is really a light brown/yellow colour as opposed to clear and it also presents the additional problem of having to clean it off in order to replain any damage that does go through to the paint. Better methinks to forget it and concentrate on maintaining the paint.

Of course the cavities are a different kettle of fish because I can't see inside heater channels and other seriously enclosed spaces to inspect/maintain them. Thus I figure that the colour of the protective wax is insignificant in these areas. The blurb in the Frost catalogue about Dinitrol Corromax 3125 says "A specially forumulated wax which penetrates rust and dirt preventing further corrosion." That sounds like just the ticket to me, even if it is brown.

Hot Spots

The final consideration is that there are a few places where special paints are needed. Exhausts and engine blocks need paint that will stand the heat and while I have no immediate plans to paint the engine block I do need to do something about the rust on my exhaust pipework. I've also obtained (from Frost) some special paint for painting brake calipers and drums.

Having formulated a plan, all I need to do now, is to get painting.

1 comment:

longlivearyan said...

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