Flint Seasonal Behaviors

Anyone noticed a difference between flint in summer and winter?

For me cold flint you have to hit a lot harder, get smaller bulbs of percussion and thinner shorter flakes. I've taken to warming it for an hour of so indoors before going out and knapping it.

I can understand this - maybe due to moisture content? its not something I have noticed as I don't knap as often as I should and also my flint is kept in my workshop.

I read a post years ago about knapping glass from bottles, the knapper was Canadian and did most of his (pressure flaking) work in the cold seasons. He would warm bottles near but not too close to his wood stove before knapping.
You would think that cold flint would be more brittle and knap better? Hmmmm...

Heat expands and cold contracts water. I believe this is the reason when you make a flint wall you can't use modern mortar because it is solid and the flint is unable to expand and contract seasonally. Instead you have to use a traditional lime mortar which softens when moist and resets when hard, constantly adjusting resetting itself around the flint. From a knapping point of view I guess a warm expanded flint is going to have larger gaps between the grain to fracture down, and cold contracted flint more solid.

Yep! true, has anyone here tried to knap ice yet? It will work apparently. Winter is coming.