1095 and O-1 are not the same steel.
If you heat O-1 red hot and then just let it cool in air it will harden. Not as hard as if cooled in oil but hard it will be. You can also cool in water but you risk it stress fracturing.
Quote:
1095
Element Content (%)
Iron, Fe 98.38 - 98.8
Carbon, C 0.90 - 1.03
Sulfur, S ≤ 0.050
Phosphorous, P ≤ 0.040
Manganese, Mn 0.30 - 0.50

Quote:
O-1
Element Content (%)
C 0.85-1.00
Mn 1.00-1.40
Si 0.50
Cr 0.40-0.60
Ni 0.30
W 0.40-0.60
V 0.30
Cu 0.25
P 0.03
S 0.03