About 5 years ago, the Tiger tanks at Bovington Tank museum received a paint job. You can learn more about the process in this video, How to Paint Tiger Tanks featuring Bovington Tank Museum Curator David Willey.
In the linked video, Mr. Willey states that German RAL tank paints used base oxides, sourced from within German territory, that never fade. This makes much sense. Molecules exposed to light absorb energy and break down. At some point, the starting molecules all break down, leaving behind less complex molecules. Eventually, this process will result in a molecule that cannot break down further under normal amounts of solar radiation. If a paint is made from molecules that cannot break down any further, it should not fade with time.
Of course, one wonders how paint bases react to sunlight but I have not gotten that far in my research. While looking for more information about base oxides, I stumbled across a recent article entitled, Pigmentless Paint That Never Fades.
I thought some of you might be interested in this new technology. In the future, it may be possible to build a plastic model with such resilient paint that it never breaks down.
Styrene also breaks down with time but for high quality styrene the process is very slow. One can imagine a styrene model with a coat of paint so resilient that energy from sunlight never attacks the paint or styrene, resulting in a near immortal model. I think that would be a rather neat trick.
My models will all be immortal, I tell my friends and family I’m getting cremated and ashes into each tank and given to everyone, each model will be a urn, that way my family can’t get rid of my models when I croak
Mineral pigments can also degrade over time, some less quickly than others.
In nearly all cases the degradation is way too slow for us mortals to notice.
My eyes will be forever closed long before the pigments in the paints I use
will have started to show discolouration.
Pigments in coloured styrene is another matter.
I built the USS Constitution (1:196) nearly 50 years ago.
The deck was supposed to be tan, I didn’t have any tan paint but since it
was already coloured I just moved on. I did paint (Humbrol Enamel) all the
other surfaces. The finished ship sat in a glass display case at the back wall
of my room, 4 - 5 meters from the window (which has metal blinds).
After 10 years the deck had turned a sickly light green colour except in the areas
just inside the “sunny side” bulwarks.
The limited amount of direct sunlight that could reach the model had managed to fade
the pigments in the plastic. The Humbrol enamel paint still has the original colour.
That essay concurs with many other documents on the subject. If a pigment is chemically simple enough, and pure enough, and not exposed to high energy, it lasts a very long time. Of course, if enough energy is applied, any molecule will atomize.
Back in 2013, another process was invented that wraps pigment molecules in a cellulose wrapper. According to the inventor, the resulting pigment molecules are remarkably resistant to light damage.
Styrene definitely has a shelf life. Recently, one of my oldest models spontaneously broke apart. That event spurred my renewed interest in the life span of plastic models.
I am very pleased that the Humbrol paints you used are holding up. My display room gets very little light such that even the card models remain in good condition after 20 years. Perhaps I should invest in UV resistant display cases, just in case acrylic paints are less resilient.
Anyway, I found it very interesting that German vehicle paints were specifically formulated to prevent fading. I intend to experiment with different painting techniques on my next few models, trying to emulate that in scale.
How old was it?
My USS Constitution is still holding up, masts, spars et.c.,
the plastic itself must be older than 50 years.
I presume that the plastic itself cracked (i.e. not the glue joints).
Our plastic models can have widely different properties depending on
manufacturer. Some East European kits have brittle plastic from the
factory …
That’s why I’ll start painting my models with 24k liquid gold - it’s completely non-reactive!
As for old glue joints, that horrible tube glue we all had in the 50s/60s/70s was terrible. It was mostly filler with a limited amount of solvent, so most joints were weak compared to what we get with Tamiya Extra Thin…
