Callusing occurs between 78 and 88F, below 76 callusing does not occur hardly at all, and above 88 the callus tissue is so soft it will break off and not form a proper union.
Here's a chip bud graft, Andre grafted onto 101-14MGT, that has just swelled enough to split the wax case:
Here's another:
And another, this one split the wax 2 days after being transplanted:
This one, an ungrafted 101-14MGT, has decided it's time to make grapes:
That top bud was a fruiting bud, it'll grow out a cane but I'll pinch off that inflorescence once the cane grows out a bit.
You can see, that it took almost three weeks for some of the unwaxed cuttings to drop the white shoots that died back, to grow out a second bud. And of those, one of them has dried up, since it pushed that second bud before growing roots.
Also in the foreground, a cutting that had swelled the bud in the callusing bag that was too wet. You can see how it trapped moisture in the wax, but then when it broke out it grew out and dried up-it didn't have enough root to absorb the water needed, or the graft union was not healed well enough.
