Inconsistent Glazes

[maggie18]

I recently had the following pieces glazed fired, all pieces were glazed from the same bottle of commercial glaze, mayco, however many of the pieces fired very differently. This is the same problem I had at a prior studio, you can see that on some pieces the glaze never even developed into glaze, there are matte spots on the glasses that did not glaze pure black, and on the outside of the 4 China Blue glasses only 1 developed into a gloss finish, although it has a big chunk of something on the front of it and the other glass has a chip on the top near the rim? 

The studio glazed fired my pieces with greenware could that have caused the inconsistencies? Also I have flakes of something on on or two pieces, I am looking for some advice on what is happening.

 

Thanks in advance.

[David Kruk]

From my experience, different outcomes with the same glaze has a lot to do with where the pot was placed in the kiln.

[Chilly]

Glaze application looks too thin ?

[bciskepottery]

Could you tell us a bit more about the glaze . . . what is its firing range (low fire, cone 5, cone 6, etc).  Do you brush the glaze on or dip?  Also, what was the firing temperature for the kiln?  Was it a fast firing or slow firing?  The glaze application looks to be thin, which often results in less than desired color and surface; it could also have been under-fired -- but need firing info for that.

 

The flakes could have come from the kiln shelves, kiln wash flaking off and falling onto your wares.  Or, the wares could have been bumped during loading and pieces of your glaze knocked off. 

[Babs]

Looks to me as if :

Glaze was not stirred thoroughy or continously between application.. the lump of oxide and glaze on the mug.

The flakes could be glaze crawl caused by dusty ware or thick sections of glaze.

Not thick enough glaze application in some areas. Some glazes are different in colour and surface where thin/thick.

And the solid matte finish, supposed to be a glossy?, not fired to the appropriate temp.

You wrote that the ware was placed with greenware. What temp. was the greenware being fired to?

Good luck with your observations, always frustrating till you get to the correct explantation for your results.

[maggie18]

Thank you everyone for your responses, temps fired I do not know, the clay is low fire and glaze is low fire glaze, brushed on,  the studio fired my pieces with their children's class pieces, low fire underglaze with clear glaze over the underglaze. 

 

Thanks for your support.

[neilestrick]

To me it looks like most of the differences are from application thickness.  Most brushing glazes need 3 coats, applied in opposing directions.