A technical question for the potties re: glaze discoloration

My damaged little early 19th century Staffordshire pearlware pitcher (discussed briefly HERE) has a hairline crack at the base of the handle. This seems to have caused a discoloration from the crack area that seeped upwards throughout the entire handle. How/Why does this discoloration happen?

 

That’s odd!. Annoying for you but a fascinating question.

 

That type of discoloration is often cause by the yellowing of a repair.

If you have a black light have a look.

 

My guess: The ceramic is probably porous and the stain spread through capillary action. Holding it by the handle would heat that area, not a lot but apparently enough.

 

This does sound likely, thanks.

 

^^ This is correct, oil and heat exacerbate the problem, which is why you see some old dishes have gone totally brown (keeping things warm in the oven).

You can fix it if you have hydrogen peroxide (30 ish percent), patience, an oven and a bit of luck (electric only, HP can be explosive). I have done it in the past but I find it not worth the trouble.

 

Soft body, it's spread.

 

My mother in law gave me a pitcher that had turned brown up to two inches below the top. She would make ice tea in it. the glaze had crazed and allowed the tea to stain .