The interrupted quenching technique is, when used by bladesmiths, a means of approximating a marquench/martemper, but is actually more akin to an industrial timed isothermal quench. The proper place to interrupt is as close to Ms as possible. I am sorry I have to use the technical term “Ms” but to give a precise temp would be misleading as Ms will change with every steel chemistry. But since we are talking about 1095 I will venture the suggestion of 400F (although this could change with different soaking heats before the quench). To interrupt too far above 500F will result in some negative results, some resulting in loss of hardness and others resulting in loss of toughness and hardness.
With 1095 if the interrupt is right at 400F, you should have around three to five minutes to fix any distortion that occurs above 275F, below this you are going to have to get it later. Any corrections I have ever done in metastable austenite were pretty stable an permanent, but the uneven stress conditions that required the initial corrections will continue to influence the 25% martensite that could continue to form after the blade has stiffened too much. Also with 1095 if there is some overheating in the austenization you will also have the annoying problem of delayed conversion after the blade is fully cool, resulting in a warp suddenly appearing in a blade you thought was hardened and cold.
Should you have a warp in a cold blade, fixing at room temp in 1095 could be disastrous. In the dagger class I just taught at Haywood College NC (the one Mace shared pictures of) the steel we were using was 1095 and many of the blades warped when the students took them home for heat treat. Warpage is about the worst to fix in a double edged blade and often results in maker giving up on it. But with a understanding of modulus of elasticity one can use temperature to your advantage. Reheating the blade to 400F will allow much greater corrective actions without fear of snapping the blade. I had students re-temper their blades above 400F and then quickly got on it with a vice, some pins and my gloved hands while they were still hot. You should have seen people scatter and shield their wincing eyes waiting for the inevitable “snap” as I pushed fully hardened dagger blades father than they normally would dare. I just laughed and said that I was not afraid because I had faith in the science! All daggers were completely straightened. I have often mentioned how the modulus of elasticity of steel is a constant, but only at room temperature, at elevated temperatures steel flexes and eventually yields very differently and brittle steels behave in a much more plastic nature allowing you to actually bend them without having to trash their hardness.
I think the other three are salvageable, though.
