Some interesting bit of science makes something that you would think impossible, possible: preserving a snowflake forever.

Being my first instructable, please forgive me for any truly heinous instructable-related atrocities I commit.

I'll be covering both the how and the why of the snowflake preservation process. If videos are more your type of consumables, then I direct you to the short video I produced:

Step 1: Materials

Here's what you'll need:

Snow (essential for best results)
A dark piece of paper or cardboard.
Non-gel superglue - new or unopened.
Glass microscope slides and slips (two slides can be used if slips are unavailable)
Fine-tipped paintbrush
Flashlight (optional, but very useful)
Magnifying glass (optional, but useful)

Snow - There's no getting around this one. Snowflake morphology (the shape of the flakes) and size depends greatly on temperature and humidity. Take a look at the diagram I've included to get an idea of what conditions are best for collection. In my experience, between 15-28F has yielded the best results.

Dark Paper/Cardboard - This is your collection surface. You want it to be dark for contrast, and made of paper or cardboard so it poorly conducts heat. We don't want the snowflakes melting when they land.

Superglue - The kind of superglue we want is the liquid type. To my knowledge, this type of superglue is pure cyanoacrylate. Gel-type superglues contain fumed silica particles that aren't visible to the naked eye and act as thickeners, making the glue more viscous. For our purposes, gel-type super glues would be very difficult to work with.

Glass microscope slides and slips - These can be found online very easily and cheaply. You may also check for a local lab supply shop. You can also use a second slide in place of a slip with good results, though I think the lightness of the glass slips makes them a better choice.

Fine paintbrush - The fine hairs of the paintbrush act as fingers to collect and manipulate the snow flakes. This item is essential.

Flashlight - Best collection times are at night, or at the very least, in the shade. The radiation of the sun, even reflecting off of other surfaces, could melt the snowflakes before you can collect and cure them. Use an LED flashlight, or headlamp, to help inspect the snowflakes. Angles are important and moving your light source around could make snowflakes you didn't see before pop out like twinkling stars. I suggest LED because you want something that doesn't give off a lot of heat.

Magnifying Glass - Optional.

Step 2: Preparation

Preparation is simple, but probably the most important step.

ALL working materials must be cooled below freezing before use.

That means your slides, slips, paintbrush, collection surface, and superglue. Storing these items in an insulated container in the back of your freezer is the best option. Placing them outside an hour before use is also an option.

Storing your superglue in the freezer, in general, isn't a bad idea. The process by which superglue cures (a form of polymerization) slows tremendously at freezer temperatures. Some manufacturers claim the shelf life of their glues can be extended indefinitely if unopened and stored in a freezer.

Dress warmly. One, to protect yourself from the elements, and two, to protect your snowflakes from your body heat. We release a surprising amount of energy, about 100 watts, and a good chunk of this in the form of radiated heat. Wear gloves that still afford a degree of dexterity, and avoid handling anything more than it needs to be.

Step 3: Collection

The collection process is straightforward, but does require some patience.

Snowfall

In a light snow and in the shade (or at night), place your dark piece of paper/cardboard out to collect falling snowflakes. Inspect the snowflakes, and if you find one you like, use your paint brush to ever so gently collect the snowflake and move it to a waiting slide. I find it useful to have the slides laid out on the surface ready to go, and just place a piece of paper over them so that snow does not collect on them.

Collecting the snowflakes with the paintbrush can be a bit tricky, but it's something you'll get better at as you go. If it's humid, the snowflakes like to stick to other snowflakes, to your paintbrush, or pretty much anything they touch. If it's dry, you may have trouble picking up the snowflake at all.

Whatever you do, do not exhale in the direction of your snowflakes, and wear a scarf over your face to help prevent premature snowflake melt.

To the glass

Once you have gently collected and moved your snowflake to the glass slide, gently place it somewhere near the center. Sometimes the snowflakes like to stick to the brush, and you may have trouble extracting it without damaging the snowflake. Try, and try again.

Superglue and slips

Once positioned, add a small drop of superglue onto the waiting snowflake. It's very important that the superglue be kept cold, and do not handle the tube for very long. Grab a glass cover slip or second microscope slide, and gently lay it atop the snowflake. Use the "wedge" technique shown in the photos to minimize trapped air. Don't use your bare hands like in the photos -- your uninsulated hands will quickly heat up the glass cover slip.

The more the merrier

Not everything in this process is under your control, and unexpected things can happen. My advice is to play the numbers game. You can have more than one snowflake under a slip, or have 2-3 slips per slide. Or just keep collecting on to slide after slide. Experiment with different techniques, and discover what works best (and let me know what works best for you!).

Step 4: Storage

In my opinion, this is the part of the step that is most difficult.

The superglue resin does not cure instantly, and in fact, will cure very slowly at temperatures below freezing. Thus, any disturbance prior to curing has the potential to ruin your snowflake. Any unexpected temperature change could also melt the snowflake before it has cured.

Here are my recommendations for storage, though you should try new things and find what works for you.

Store slides horizontally, slip-side up. You don't want gravity moving things around.
Store in an insulated container packed with snow.
Avoid handling slides, and when you must, handle them by the edges, as far from the snowflake as possible. Heat will conduct through the glass.
When moving from outside to freezer, be quick about it -- this is why an insulated container is useful.

You can also get some insurance by storing your slides in more than one place, using more than one method, just in case something goes wrong.

Store below freezing for 1-2 weeks. Maybe even leave some undisturbed for a longer period of time, and see if these turn out better. Frankly, I no longer live somewhere where it snows, and can't experiment.

Step 5: Results!

If you were patient and meticulous, you will be rewarded with snowflakes that are permanently cast in resin.

Unfortunately, I've given the best snowflakes to friends and family as gifts over the years, and the ones I still have (and shown here) are the rejects, but the illustrate a few points.

The process is imperfect: Air bubbles may arise in the curing process, or become trapped when first setting the slip down. Melting and/or the chemical reaction tends to soften sharp edges. It's unclear to me whether this is an unavoidable result of the chemistry, or merely storage/handling.
Bigger is better: Big snowflakes have much more of a "wow" factor and are more forgiving of your mistakes. Small snowflakes preserve well too, but are much more difficult to see.
Some white/some transparent: Some snowflakes cure to a white surface, while others cure transparently. I'm not sure what factors cause one over the other, but I suspect humidity and the speed of the curing process play a role.

Take notes

If you're interested in learning what works, what doesn't, and what conditions are best, take notes on your collection day. Also, once your snowflakes have cured, it's a nice touch to write onto the slide (with a fine-tip sharpie) the collection date, time, and location.

Preserved snowflakes make excellent gifts, and are truly unique. Trust me, you'll impress someone.

Step 6: The Science

The reason we can preserve something as delicate as a snowflake with super glue is because super glue is actually activated by water. In fact, without moisture, super glue would be pretty useless as an adhesive.

Specifically, the hydroxide ions (floating around in water, along with their H+ counterparts) give up their extra electron and bond with the double-bonded carbon, which forces the electron in the adjacent double bond to hop on over to the neighboring carbon atom. This new molecule now has an extra electron to donate, and will react with other cyanoacrylate molecules, which, in turn, moves the free electron to the newly bonded molecule.

This process continues in what is known as living polymerization. Living, because the reaction has no termination step. The polymer chain will continue to grow so long as free molecules (monomers) are present, and there are no impurities. As a result, very long chains form throughout the liquid, thickening the resin, and ultimately bonding materials together.

The good news is that the the polymerization should be initiated at the snowflake/glue boundary, and so should begin to preserve our snowflake immediately. The bad news is that the reaction is exothermic and produces some heat -- whether this heat is sufficient enough to cause melting is questionable and I'd have to run through the calculation. However, this is why manufacturers warn of spilling super glue on clothing. The cellulose in cotton materials rapidly initiates polymerization and in turn releasing large amounts of heat -- enough to burn you!

The rate of polymerization also slows significantly with decreased temperature. In fact, some manufacturers claim that the shelf life of their unopened superglue can be extended indefinitely if stored at freezer temperatures. This is a problem for us, as we want to keep our snowflakes from melting, but also ensure the resin cures in a timely fashion. So, store them somewhere pretty cold, but not too cold? Frankly though, I wouldn't worry about this -- just ensure they are in a freezer for a few weeks.

Step 7: Closing Thoughts

My biggest piece of advice, as I mentioned earlier, is to experiment and find what works. If you find something that works better than I described, by all means share it! These are things I want to know, too.

Because the act of snowflake preservation is slightly destructive, I'm of the opinion that the purest form of snowflake preservation is photography -- though it lacks the tangibility that makes this process so special. In terms of photography, the images I've attached were taken without a fancy macro lens (I just used extension tubes and a zoom lens on my DSLR). If you have a microscope, the quality of photos you can capture of snowflakes is phenomenal (see the link below). However, that's a topic for another day.

Share your results. Stay warm. Good luck!

The best resource on the web for all things snowflakes, including preservation:

http://www.its.caltech.edu/~atomic/snowcrystals/pr...