Yixing crack in the kiln or by 'accident'?

[betta]

Hello teachatters, I believe almost all yixing teapot users have experiences seeing pot s having small 'hairline' or crack.
It presents most of the time with old pots.
Some people said if the pot is cracked in the kiln, the crack won't grow.

I'm asking for your experiences whether it's true and how to differentiate whether such a crack is due to firing in the kiln or due to 'accident'?

Thanks in advance for any comments

[chrl42]

Cracking happens when crafters were sloppy at controlling the temperature of a kiln. Every clay needs different temperature and different method of heating.

For example, Duanni and Luni are most sophicated clays when it comes to heating.
So crafters heats em at highest temperature at once then take out and put it again with a lower temperature and repeat those method.

Luni is said to be most difficult clay to make because unlike Zhuni, a defect of Luni can be found after being made, in this case with a crack..that from sometime unknown cracks shown while brewing and gets bigger as time goes by

Cracks made in a kiln, well I don't have experience on this one..

[hop_goblin]

No to mention the shrinkage from Zhuni causing cracks.

[bearsbearsbears]

Cracking happens when crafters were sloppy at controlling the temperature of a kiln.

There are other reasons for cracking in addition to poor kiln control. If the pot isn't evenly and slowly dried before firing, it will crack. This happens if the walls, lid, or handle are of uneven thickness: thicker parts retain more moisture. Dryer parts pull away from wetter parts, and cracks occur. For this reason, i think, i've noticed most hairline cracks around spouts, handles, feet of pots, and where knobs connect to lids.

[betta]

Cracking happens when crafters were sloppy at controlling the temperature of a kiln.

There are other reasons for cracking in addition to poor kiln control. If the pot isn't evenly and slowly dried before firing, it will crack. This happens if the walls, lid, or handle are of uneven thickness: thicker parts retain more moisture. Dryer parts pull away from wetter parts, and cracks occur. For this reason, i think, i've noticed most hairline cracks around spouts, handles, feet of pots, and where knobs connect to lids.

Thanks Chrl, Hop and Bears
So both sloppy temperature control in the kiln and post firing added with shrinking rate of specific clay cause this. But does anyone know if the crack due to postfiring enlarge if the pot is subjected to liquid?

[hop_goblin]

The will constantly stressed due to the contraction of the clay as it turns from hot to cold which can enlarge a crack. You may notices this in a zhuni when you pour water over the lid after the pot is filled for the infusion. Next, poor the water far from the spout . When you do you should notice that water is coming up to the end of the spout. This is due to the contraction of the clay.

[Bert]

The will constantly stressed due to the contraction of the clay as it turns from hot to cold which can enlarge a crack. You may notices this in a zhuni when you pour water over the lid after the pot is filled for the infusion. Next, poor the water far from the spout . When you do you should notice that water is coming up to the end of the spout. This is due to the contraction of the clay.

I think the water coming out of the spout has to do with the volume expansion of the water when it gets more heat. The clay won't shrink anymore because it is already fired.
The clay expands when heated up from the water and contracts if cooled down. You are right - this could force a fine crack to grow big.