A technical question for the potties re: glaze discoloration

Discussion in 'Pottery, Glass, and Porcelain' started by bluumz, Apr 11, 2021.

  1. bluumz

    bluumz Quite Busy

    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?

    2CF98EE8-5386-47CF-96A7-4DCBDBEBCEEA.jpeg
     
    KSW likes this.
  2. KSW

    KSW Well-Known Member

    That’s odd!. Annoying for you but a fascinating question.
     
    bluumz likes this.
  3. say_it_slowly

    say_it_slowly The worst prison is a closed heart

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

    If you have a black light have a look.
     
    bluumz, KSW and Any Jewelry like this.
  4. moreotherstuff

    moreotherstuff Izorizent

    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.
     
  5. bluumz

    bluumz Quite Busy

    This does sound likely, thanks.
     
  6. Ce BCA

    Ce BCA Well-Known Member

    ^^ 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.
     
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  7. Ownedbybear

    Ownedbybear Well-Known Member

    Soft body, it's spread.
     
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  8. Lark

    Lark Well-Known Member

    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 .
     
    bluumz likes this.
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