As a wee lad, I tried saving snowballs to break out in the heat of summer hoping to surprise my brother in the back of the head. I never quite ended up with fluffy goodness; I always opened the carefully sealed Tupperware to find dense ice-bombs (not something to hurl at an older brother).
Well, it’s been many years and now that spring is nigh (it is nigh, isn’t it?) and I have a four year old who [del]can’t fight back[/del] will be just as excited to save snow for the summer.
…and just as disappointed when he finds lumps of ice.
Is there anything I can do to help out? I figure that as an [del]grown-up[/del] old person with access to vacuum sealers, blow torches and freezer thermostats and the Internet, I might be able to help him achieve better results.
The problem you have is that whilst the water is frozen - ie not liquid, you have not stopped all the interesting processes that the water undergoes. Water sublimates, that is even when frozen, it turns directly into water vapour. (Freeze drying is a process that makes use of this effect, allowing you to dry out something whilst preserving it structure. Hint - if you have a a sodden book, you can dry it out without further damage by putting it into a frost free freezer - it will take many months, but it will dry it.)
If you have water in a sealed container in a freezer, it will sublimate, and then later then vapour will precipitate out again. This runs is a continuous steady cycle, the result of which is that the fluffy (large area) snow tends to turn into a mass that has less surface area, and you end up with a lump of icicles.
The colder you keep it the better, but even in liquid nitrogen you will only slow the process. High pressure would also help. But a cryogenic pressure vessel isn’t usual domestic equipment, and I don’t know how much it would help, only that it would help to a degree.