Referencing this post from a few days ago.

The best guess as to what was causing cracks during throwing was that the clay had been frozen, and the top recommendation was to either dry it out and remix, or to mix in some fresh clay.

Having never had a bag of clay freeze on me, I thought I'd run a quick test. I wedged some clay (3.75 pounds), divvied it up into three even balls, and then:

• ball #1: thrown immediately, I made a small bowl (this is the control)
• ball #2: into the freezer for several hours until solid, then thawed, then thrown (first trial)
• ball #3: into the freezer alongside ball #2, then thawed alongside ball #2, then re-wedged, and then thrown (second trial)

The control proceeded normally, no surprises there.

For the second ball, the moment I slammed it down on the bat it showed cracks that seemed to follow the spiral of the layers formed by wedging. However, after coning up and down, I was able to throw normally – no cracking – and made a second bowl, same as the first.

For the third ball, I started by re-wedging. I use stack-and-slam wedging, which basically goes like this:

1. slam the clay onto the wedging surface (I have a smooth concrete slab)
2. use a wire to split the clay – wire is held parallel to the front edge of the wedging surface, so you get a "front" and a "back" lump
3. lift the front lump, turn it over so the top becomes the bottom (but left and right stay in place) and slam it down onto the rear lump
4. pick the whole thing up, turn it upside down, and then rotate it 90 degrees (so left becomes either front or back)
5. slam the whole thing down onto the surface, and the process begins again.

I typically do this 16 times, then spiral or rams-head knead depending on how much clay I've got (small amounts don't spiral-knead very well).

For that third ball, when I slammed the ball down on the wedging surface, those cracks appeared again, but much more pronounced (probably because I used a lot more force). By the time I was done wedging and kneading they were gone.

Back at the wheel, I threw down that third ball of clay onto the bat – no cracks at all. And throwing proceeded normally (a third small bowl).

My takeaways here are that yes, freezing the clay will definitely cause problems with cracking. However, you shouldn't need to fully dry and re-mix the clay, nor should you need to mix in fresh clay from another bag. A good wedging should be all that's needed.