That's interesting.

I've never heard of doing that before.

The science: according to thermodynamics, solids expand when heated, and contract when cooled. In reference to the topic: when you boil leather, it is drying it out by vaporizing the excess water. This allows the leather to become harder as a converse to leather being easily pliable when wet. If you freeze it, it contracts the leather faster after the water is vaporized, therefore your leather will harden faster.

Depending on how you did your hardening it should have been hard almost immediately...the drying time on wax is about 1 minute to firm and under an hour to totally cured. Water boiling should be instantaneous....

If you water boiled the leather it will not have the same properties as waxed as it will not be resistant to mold nor will it be water proof. water boiling leather changes the molecular structure and plasticizes the leather. Waxing simply soaks wax into the pores and fills them with wax. Oil boiling, water boiling and baking are the most authentic but waxing allows you to retain the shape you cut out without having to consider shrinkage or warping (baking does this too but doesn't harden the leather much).

I"m told that wax treated leather is easier to cut with a sword. :)

I'm told that you can't stab through a Kevlar vest with a knife.

There is video disproving this. Anatole used all of his tard rage to do it though.

Wax acts as a lubricant and doesn't truly do anything to the structure of the leather other than filling the "gaps" with wax essentially turning it into a leather candle and we all know how well candles do against a sword (watch any fantasy movie out there). My main issue with boiling is that it warps the leather and shrinks it. If I knew how much it was going to shrink it wouldn't be too much of an issue as I could simply blow my pattern up by x% unfortunately the warping that occurs often leads it to be unusable leather that is too shriveled to be of any use. I may try experimenting again with my new armor grade leather as the last attempt was with some 8-10 oz leather.

I actually just read an article on functional armor on myarmory.com yesterday and was surprised at what riveted period maille can actually stop and can't stop. I'd be interested in seeing what some period cuir boilled leather (perhaps lamallar or lorica segmenta) would be able to stop. Perhaps next crown qual I'll have some new armor done.

Best way is to not boil it at all. All my leather armour was hardened at sub-boiling temperatures, when bubbles just start to form at the bottom of the pan. Then I moved on to the historical baking method. Soak the leather and shape it, then cure it in a low temp oven until dry. To finish coat with hide glue (rabbit was evidently the period choice). I usually skipped the hide glue cause it can be a pain to work with. The idea is to keep the leather from reabsorbing moisture (which also happens with the boiling method, just takes longer), so I just gave the leather a thin coating of micro crystalline paste wax or melted beeswax. Lacquer also works okay, but I find that most leather lacquers tend to be a little on the thin side and the leather soaks up way too much.

Do you presoak the leather in water letting all the air bubbles flow out before you start the "sub-boiling"? Do you just take dry leather and toss it in the warm water or do you put the leather in and slowly raise the temp? When I first started doing hardened leather about 3 years ago I did experimentation with various methods and eventually settled on wax as it provided the best results for non live combat.

I did both presoaked and straight from dry with very little appreciable difference. I did find that putting the leather in and slowly raising the temp seemed to result in more unpredictable shrinkage because I had less control over the final temperature:time ratio. Sub boiling was my preferred method at the time because the only methods presented back then (2001) were boiling and waxing. Once I learned about baking and sealing the leather, though (2003 or so) I stuck with that since, once you have the method down, I find it to be the most reliable and controlled way to harden. The downside is that it's so dreadfully slow. My problems with wax (aside from it being non period) are that it makes the leather weigh twice as much in some cases (something we really don't need since the people who created the armour rules for 7 decided we should all wear saddles rather than armour), and in the heat down here (Florida) the wax can melt and even sweat out when it gets hot enough.
Of the quick methods, though, wax is the most consistent and some people do prefer the way it looks and feels.