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#1 Ecurie Martini

Ecurie Martini

    Ecurie Martini

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Posted 18 April 2018 - 02:23 PM

Airbrush Adventures  (Part of a build thread on 1/32 resin-bodied C type Jaguars)  The C type body shell as supplied includes a resin exhaust system, 2 different vacuum formed cockpits (one deep, one shallow) and vacuum formed windscreen and headlamp covers. The body shell is very well prepared with cockpit and wheel openings accurately finished. There’s not much to do besides fitting body mounting posts, painting and adding details so I’m going to focus on the painting process.

After fitting the body mounts, the body received a very light sanding and a thorough washing. When dry it was primed with my favorite Tamiya gray primer. After 24 hours a 2nd coat was added, allowed to dry, very lightly sanded and washed again. The finish coat, Tamiya Racing Green was applied and set aside to dry. On inspection, I found something very strange. The paint, primarily along the edges of the wheel wells and the lower edge of the body was very rough. It was not “orange peel” or overspray – it looked like a collection of very tiny craters as if bubbles have formed and burst. I could not account for so I simply sanded down the affected areas and re-sprayed. The same thing happened. I have been using rattle cans to spray models for more than 60 years and have never seen anything like this. I thought that perhaps the can, of indeterminate age, had gone off in some fashion. I thought about getting another can of paint and then decided on a different approach.

I have been using an airbrush for quite a long time. I use it primarily for detail work especially applying AlClad metallic lacquers. One or two occasions when I could not find a suitable rattle can (e.g. a BRM V-16) it was used for a whole car.. I have been curious about the various model automotive lacquers such as MCW and Zero Paints. I decided that this would be a good time to try some. Naturally, having been a scientist, the first thing that I do on any new project is to look at the literature. I found the following lengthy but I believe, worthwhile, discourse.

https://www.youtube....h?v=O2QKwiwFjGw

It is almost an hour long but I found it very instructive. It made me aware of a 3rd source of model lacquers, Gravity Paints and offered a comparison of this product with the Zero colors. In addition it taught me that, for whole body painting, I had been using the airbrush incorrectly (too far away)

I ruled out MCW because they do not offer a two-part catalyzed clearcoat. I wanted to try one of these for its presumed hardness and durability. I don’t mind dings and scratches on a car that has been raced but I become really unhappy when the decals become tatty. Zero was (locally) out of stock on some of what I wanted so the order went to Gravity.

My order arrived and I settled in for a painting session. I had ordered primer, color and clearcoat. I proceeded in what I thought was a logical fashion. Without stripping the existing paint, I sanded the body all over to a flat finish and eliminated all of the craters. I then sprayed the primer to provide a base for the color coat. This was a big mistake! Looking at the result, my immediate thought was is there any precedent for a “faux lizard” livery? It was obvious that the primer solvent was very aggressive and had turned the underlying enamel into crackled islands of green.

A few rags and some solvent later saw the body stripped back to its bare resin. I then proceeded with the primer using my Iwata top loading airbrush at about 18 psi. Following the video noted above I laid down a few mist coats and gradually built up fuller coats to complete coverage. One of the advantages of these lacquers is they the flash off so quickly that, with only a few pauses, this can be a continuous process.  This was done in the morning and by evening I decided that I could proceed to the color coat.  I did not rubdown the primer (we shall come back to that later) the color coat went on just like the primer. After an overnight dry and again without rubbing out, I proceeded to the clearcoat. This is a catalyzed coating and requires mixing coating, thinner and catalyst in the proper proportions. Like the previous applications, I began with mist coats and gradually increased the paint volume to get full glossy coats. The air pressure/paint volume/distance combination is critical in this step to avoid orange peel.

After 24 hours I proceeded to apply the decals. I also applied some decals to a painted test panel. Since I have found that, at least in my hands, even several liberal coats of acrylic floor finish is not adequate protection for the decals, it was my intent to clearcoat them. I have had some success in the past with spray on clearcoats carefully misted on prior to full coverage without damaging the decals. I tried this on the test panel with the catalyzed clearcoat. Even the lightest mist coat turned the decals to something resembling porridge. I was not happy. I decided to try and invoke chemistry in its most basic form: oil and water don’t mix. I gave several of the remaining decals on my test panel 2 liberal coats of acrylic floor finish and allowed it to dry overnight. Back to the airbrush – a couple of mist coats showed no signs of damage. Encouraged I added heavier coats up to full gloss coverage – not a wrinkle! The decaled body was re-sprayed and left to dry.

 

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The finished product does indeed have a few wrinkles in the decals but they were ones left unresolved by the decals setting solution – these decals came out of my collection and I have no idea of their age.  Time will tell whether the application of the catalyzed finish over the water-based acrylic will have any effect on its adhesion or protective properties. For the moment, although I still have a lot to learn about using these finishes I am happy with the result.

I cannot account for the white spots evident in the photo. I do not see them when looking directly but, as I think most of us know, a camera lens is far less forgiving than the human eye. Close inspection does reveal some places where there was a bit of orange peel and the surface is not as good as it could be. One of the cars, number 6 is already on its travels but the other one, number 6 will not see action for a couple of weeks so I’m going to try to rub out and repolish the paintwork to see if it can be improved.

Two number 6’s?  Not a typo – separate competitions so the duplication is not a problem. Why number 6? – Reference to an old favorite “I am not a number, I am a free man” (and yes, I have visited Port Merion)

Caveat – these finishes dry very very quickly thus quick and very thorough cleaning of the airbrush is imperative. I use a top loading airbrush that has a very short paint path. Even with this, I have had to take it apart and re-clean once. The total amount of paint used is very small and re-filling in the small cup fits in nicely with the workflow.

 

EM
 


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