Dark in the middle sounds like heart wood getting very hard I guess. Usually wood splits easier green but not always. Sometimes you just get something hard to split.
I find this sort of wedge best, but I hate all wedges.... If your saw is big enough then don't waste too long fighting with wedges.
https://www.toolstation.com/roughne...PsadD6dWfAT07omIFgpQqZadErJkOArhoC3J4QAvD_BwE
I find this sort of wedge best, but I hate all wedges.... If your saw is big enough then don't waste too long fighting with wedges.
https://www.toolstation.com/roughne...PsadD6dWfAT07omIFgpQqZadErJkOArhoC3J4QAvD_BwE