You can see a lot on just one black car. The nearly uniform appearance of white frost shows, upon closer inspection, a variety of forms. The first black car of yesterday morning didn’t seem so striking, and I considered passing it by. But, thinking of something that happened a few weeks ago, I hung around and took some pictures. You see, a few weeks ago, I discovered in my morning photos one picture that looked like snakeskin. It was the only one like it in my entire collection, but unfortunately a bit fuzzy. So, I swore thereafter to always look at the photos as I take them, then if something really new comes along, I can take many shots and hope that at least one is in good focus. Luckily, I stumbled upon the snakeskin frost on this car, but once again, only took one shot (alas - it also looks fuzzy). I guess I'll never learn.

If you click on the picture and zoom in, you'll see that the crystals are shaped  like thin disks, laid down nearly flush against the car roof, like the scales on a snake’s skin. The bright crystals are the ones oriented to reflect the sky, whereas the dark crystals have a different orientation. These disks are tabular forms like the hexagonal plate, except without the flat, prismatic sides. But the same roof also had columnar forms:

These columns are not aligned; rather, they point in many directions, a bit like blown-down timber. Notice that here all the crystals are columns, just like all the crystals were disc-like in the previous shot. So, whatever causes these shapes must be some local condition that all crystals in the region experience. Hoar crystal shapes, like snow crystal shapes,  are extremely sensitive to temperature. My guess is that the place where these columns formed was a little colder than the place with the discs. This guess is consistent with the columns being on a ridge that sticks up: the factor that determines how much a surface will radiatively cool is the view of the sky; a greater view gives greater cooling, and the ridge has a greater view.

But there were more than just discs and columns. One type of formation I’ve seen before, always on glass windows, is something I call the cactus pattern. The pattern has parallel streaks where rain has run down and spiky crystals sticking out. The images I took didn’t come out too well though, so I will have to find one of my previous images and post here later. But a similar thing, except without the parallel streaks, happens on a horizontal surface:

The above image is interesting because the tabular forms come in several types, from disc-like to serrated to nearly facetted. I’ll let you guess what this next thing is.

This next shot appears to be the parachute part of a plant seed, like that of a dandelion, with ice crystals on its parachute hairs. However, this is no seed – to my eye it was like a small frozen droplet with hoar. I wish I had touched it and melted it, to see if it was all ice, but I rushed on to the next shot.

The windshield had some other patterns. One I called ‘pine bark’, as it had the scaly look of some pine trees around here.

And near the base, a different pattern (slightly fuzzy, unfortunately):

Finally, a region with small drops packed together. I call this pattern plant-cell frost.

When I first visited Japan 20 years ago, nearly every car was white and, except for the black taxis, a black car was rarely seen. I was told that black was associated with the yakuza, the Japanese type of organized crime.  And no one except the bad guys would want to be associated with that. Nowadays I see just as many, if not more, black cars than white. If the owners of any these cars were yakuza, I doubt that I would still be taking my outings. I’m thankful for that.

- JN