The Maltese Cross in Pond Ice

January 21st, 2010

A few days after my encounter with the pawprints and grey muck, one of the ponds did freeze over. After me and my camera spent about 30 minutes admiring this rare event, I went and ruined the complete glaze job by punching a hole in it. Although the top surface had lots of interesting curves and shallow grooves, the underside, only about 8-mm below, was flat and featureless. I suppose this is because the surface marking the melt-line (i.e., 0 degrees C) is flat. But when I put a piece of pond glaze between two polaroid sheets, with one polaroid 'crossed' to the other, I saw an odd sight.

The large black "X" that appears here is sometimes called the "Maltese cross". Elizabeth Wood, in her classic little book "Crystals and Light", calls it the "black cross". And when I looked up some cross shapes online, I thought the above figure looked more like the German "iron cross". Anyway, whatever you call it, it doesn't seem to fit the scene.

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Reviews in McClatchy Newspapers

January 19th, 2010

On Monday several of the newspapers for the McClatchy company ran a review of The Story of Snow in their "Read It:" column.  An excerpt: "Part science, part art, this beautiful book explains a bit of the chemistry behind winter's cold, white precipitation and also features startlingly detailed and amazing photos of ice crystals."

Here's a link to the review in The Sacramento Bee:

http://www.sacbee.com/848/story/2452637.html

Monday evening also brought a bit of snow to SW Michigan. The crystals were not terribly clean or symmetric, but here are a couple of snaps:

Snow Crystal Photo
Snow Crystal Photo
- Mark

Strange Pawprints in the Ice

January 15th, 2010

On account of the recent cold spell, I went up the hill behind us in search of a glazed-over pond. Ponds can have interesting freezing patterns and, if the ice is thick enough, a little excitement. I've never seen these ponds freeze, but then again, I've never thought it likely enough to warrant a visit in winter. The first two ponds I visited (technically, man-made reservoirs for flooding the rice fields) had ice only over a small section at one end. I had better luck with with a drained pond. This 'pond' looked more like a dirty mud pit, but I saw evidence of ice on one side. So, ignoring the warning signs (more on that later), I walked down and around to the icy end. From eye-level, and even from a crouch, this ice looked like snow.

But except for the holes that exposed the dirt underneath and the twiggy matter on top, the surface was smooth and level, like that of a glazed pond or puddle.  Indeed, a partially glazed-over pond is probably what it had been. The whiteness was due to some fuzzy growth underneath that I could see in the large gaps (see the image below).

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NSTA Recommends: The Story of Snow

January 14th, 2010

A little while ago I mentioned that The Story of Snow was named an Outstanding Science Trade Book for 2010 by the national Science Teachers Association and Children's Book Council. Here's a link to a review that appeared a couple of days ago on the NSTA's website:

http://www.nsta.org/recommends/ViewProduct.aspx?ProductID=19598

To quote reviewer Diana Wiig: "I loved this book! What a wonderful combination of art and science. The explanations are thorough, yet simply stated. The photos/illustrations are exceptional."

We're in the midst of the January thaw here in Michigan, with balmy temperatures up to 40F and yesterday a rare sunny day.No new snow crystal photos for now.  

Here's an old  photo -  taken on film in 2003.

Snow Crystal Photo
- Mark

Snakeskin Frost and Other Curiosities

January 12th, 2010

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:

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Frost World

January 9th, 2010

Whenever I am taking a picture on macro near the maximum close-up to an object, the aperture on my little Canon automatically sets to the maximum size, which means that the resulting  images  are in focus only at the center. Ever since I got the camera in late 2008, I've wondered how to get past this problem. In flash mode, the aperture decreases, extending the area of focus, but the image gets overexposed. Yesterday morning, I finally hit upon the (obvious) solution: set the camera to flash mode, but block the flash with aluminum foil. I had thought before that the result would be too dark, but with some white hoar in the picture, the image is bright enough. (Later I found that the image is fine, though a bit dark, even without hoar.) For a reason I don't understand, the exposure time is still relatively long with the flash on and the ISO value set low, so I probably need to better stabilize my little makeshift wooden 'tripod' and set a longer delay to allow vibrations enough time to damp out. Even so, the improvement gives me more room to explore in the miniature world of frost, which I call 'frost world'. For example, the image below, taken on the roof of a black car yesterday, shows some pyramid structures sticking up, a few valleys, straight ruts, straight streets, and parallel curving streets. The basic structure was laid down when the film of condensed water froze, which I call "film frost" (though it has no standard name) and then later hoar crystals grew up off the surface, adding a little white to the landscape. In this image, nearly all of the hoar is hexagonal.

When I took a picture of a frosty leave, the image in my viewfinder had an odd out-of-focus look (below), so I took a bunch more shots.

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They Came From Out of the Tub

January 8th, 2010

Last night it rained, but the skies cleared before morning, letting the air temperature drop to about 2 degrees C. The weather, it seemed, would be perfect for lacy white frost patterns on cars. But it didn't quite turn out that way. A little bit before sunrise, I went out on my rounds. I took a few pictures of ice on parked cars and then headed for the rice fields. Neither tub had ice, so I walked to the abandoned car on the other side of the roadway. Nothing of note there either, but in those few minutes a blade of ice had started across one tub. Soon there were several. With a stick, I went under one blade, lifted it up, and noticed the thin serrated fingers that had been growing into the water, hidden under the surface. The disturbance of the water surface caused the growing mesh of ice lines to drift, unattached to the tub walls. I don't see this in puddles. In the puddles, the ice is always anchored to the shore, presumably because the ice starts from the shore, where there are more things to nucleate from.

In the tub I saw a curvy piece and fished it out. Laid out on the rusted lid of a nearby barrel, the ice looked strange, like a fossil of some prehistoric creature.

The critter is about 3-4 inches head to tail and paper thin. As the crystal grew from liquid water, called 'melt' by material scientists, it is said to be "melt-grown". I call such crystals "puddle crystals". Anyway, soon ice was starting on the other tub. Out in the middle of an open patch of water, I saw a small hexagon. With a stick I tried lifting it out.  I  found that the central hexagon had six large branches that had been hiding just under the surface. But the crystal slipped off my stick and cut under the water's surface - never to be seen again. Needing something better than a stick, I found a piece of a plastic lid that had been left in a nearby ditch and tore off a piece. Then next time I saw a small, isolated hexagon, I lifted it out and put it on the barrel lid.  See the photo below.

Though the central hexagon that I could see on the water was less than a half inch across, the full crystal was about one and a half inches across. Curious how the water would cover up all six branches symmetrically...  Anyway, despite the large width of our 'puddle star', it too is paper thin.  And being so flat and featureless on both sides, it evenly reflects the bluish skylight. The serrated pattern on the branches make this crystal a dendrite, like the dendritic snow crystal. But a puddle crystal grows much faster than a snow crystal because the melt (i.e., liquid water) is more densely packed with water molecules than the air from which snow grows. Also, when a snow crystal branch grows, it removes water vapor from the nearby air. This depletion of vapor is most severe near the base of the branches, and thus snow-crystal branches hardly widen - they mainly grow at the tip and at the tips of the side-shoots (called side-branches). But the melt is never depleted of water molecules, so the branches of puddle crystals keep widening until they merge. Another difference between puddle crystals and snow crystals is that puddle crystals viewed broadwise have a curving outline. The snow crystal usually has a polygonal outline, that is, made from straight lines.

- JN

 

New Reviews in The Washington Post and the Fort Worth Star-Telegram

January 7th, 2010

Here are two new reviews of The Story of Snow:

Washington DC has seen a bit of snow of late, on the heels of that the Washington Post says "The engaging "Story of Snow" -- featuring a succinct text, spare illustrations in gray-and-blue hues and magnified images of gorgeous snow crystals -- explains how snow is made ..." The full review is here:

http://www.washingtonpost.com/wp-dyn/content/article/2010/01/05/AR2010010503378.html?wprss=rss_print/style

Down in Texas they see a little less snow, but currently are experiencing a cold snap. Maybe it's a chance to take a close look at some snow crystals. The Fort Worth Star-Telegram has this to say about The Story of Snow:  "Part science, part art, this beautiful book explains a bit of the chemistry behind winter’s cold, white precipitation and also features startlingly detailed and amazing photos of ice crystals..." The full review:

http://www.star-telegram.com/family_day/story/1870342.html#tvg

A bit of snow is in the forecast for SW Michigan, so I have my fingers crossed.

- Mark

A Few More Lighting Experiments

January 6th, 2010
Snow Crystal

I'm continuing to work on taking snow crystal photos to the next level. It's funny because in past years I tried different approaches to lighting, and none of them worked. So it was a surprise when I picked up a couple of spare C9 holiday lights, dropped them on the flash, and suddenly saw a whole new range of colors in the snow crystals.

I tried similar things in the past, but they just haven't worked. Then I realize that I've been fiddling with the exact placement of the flash beneath the coffee can that holds the glass plate full of snow. Adding the colors, combined with the way the light from the flash was bouncing around inside the coffee can, did the trick. Insanity has been described as doing the same thing over and over, hoping for a different result. But sometimes it turns out, you're not really doing the same thing and you may have learned something new, even if you don't know it.

Now, if only the snow would cooperate. Here are three shots from last night. The lake effect bands have been running to the west of Kalamazoo these last few days. Every now and then one drifts our way and brushes against the city.  If I'm lucky I get half an hour, maybe a little longer, before the band of falling snow wanders back. Unfortunately, the snow that has been falling hasn't been the most photogenic.

The crystal at the top of this post landed on its side. I knew that it would exceed the camera's depth of field, but I liked how it looked in the finder. It's easy to imagine the crystal falling through the atmosphere. Below is a  simple crystal that has a 'spur' (as I'll call it) growing perpendicularly out of the center. I see many of these - I'm not sure why they form. The crystal is also spotted with rime.

Snow Crystal

Lastly - here's another double crystal, similar in basic structure to the one I posted on 12/27, but with much greater difference in size between the two crystals that make it up. As always, click on an image for a larger view.

Snow Crystal

 Let's hope for more snow, soon!

Mark

The Crystalline Beard

January 5th, 2010

I have very often in a Morning, when there has been a great hoar-frost, with an indifferently magnifying Microscope, observ'd the small Stiria, or Crystalline beard, which then usually covers the face of most bodies that lie open to the cold air, and found them to be generally Hexangular prismatical bodies…

The above passage, from Robert Hooke's Micrographia (1664), describes almost exactly what I do on sufficiently cold winter mornings. Though I don’t have a microscope, I have a Canon Power Shot camera with the macro feature that allows me to zoom in on tiny objects. (The best gift I ever got, and possibly the best thing an amateur naturalist like me could ever receive.) From afar, most hoar frost looks similar – a dusting or coating of white on any surface that can cool enough for vapor to deposit. The effect on an object can be beautiful, looking like an artist has applied a white highlighter to the small protrusions and ridges on the object, as in the rock below.

The rock is about an inch and a half across. The crystals range in size, but the larger ones are about as wide as three thick hairs (300 microns) laid side-by-side. One can see in the enlargement below that many of the crystals have a hexagon shape – like a snow crystal.

A better example showing hexagonal crystals is in the frost I saw on the roof of a black car a few days ago.

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