I never use cone packs. If there's a problem with the firing, the controller will shut it down. If the thermocouples are out of whack, I'll see it in my glazes and having the cone packs won't matter.
I recommend witness cones in every firing . . . unless you doing routine firings and can tell visually whether the ware was fired properly. If you know what the glaze will look like when over or under fired, you don't need cones.
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