glazing vitrified pots

[Stephen]

not to alarm anyone who has accidentally bisque fired to a vitrified cone temp by mistake and then used one of the various tricks to get glaze to stick. I have always been curious why shivering is not a possible outcome of glazing vitrified clay. My logic is that part of the bond between the clay and glaze is the soak that occurs when a pot is glazed in a porous state' Since this is eliminated by firing the raw clay to maturity I worry that instead of a good glaze fit it will instead just become a tight fitting glass shell around the ware more likely to shiver off over time if it gets the slightest hairline crack over the years.  Ditto for any intentional crazing.

To be clear I have never seen this raised as a possibility and it may not be.  Just wondering if one of you can enlighten me. While I haven't made this mistake yet there's a lot of years left for me to do so and I want to decide now if/when that happens if I want to grab a can of spray net or pile my pots in the oven and heat up to try and salvage the load.

[Babs]

WellbI have put more glaze onto an already glazed platter..all over and got shiverinf

[GEP]

If I made this mistake, it would take me two days, possibly three, to remake one bisque load of pots. That’s a lot less time and energy than figuring out how best to get glazes to stick, and then worrying whether the glazes will start shivering six months later in a customer’s house. 

[Stephen]

14 minutes ago, GEP said:

If I made this mistake, it would take me two days, possibly three, to remake one bisque load of pots. That’s a lot less time and energy than figuring out how best to get glazes to stick, and then worrying whether the glazes will start shivering six months later in a customer’s house. 

That's what I figured, just not worth the risk. I tried a few of the crack repair tricks once mentioned here as well and ended up just tossing the pots. I think I asked the question and folks dialed me in on some blends that they used and it seemed to work OK  (used a couple of suggested goos) on several pots that had accumulated on the shelve with small cracks and the glaze covered it up fine but I just couldn't sell them to anyone. Just bugged me too much that down the road the pot might fail.

Prob like removing a band aid, less painful if its done quickly, just bag'um up and toss them without even thinking about it. 

[Stephen]

1 hour ago, Babs said:

WellbI have put more glaze onto an already glazed platter..all over and got shiverinf

ouch, hope it shivered in your studio and at the customers home.

[Callie Beller Diesel]

It’s common in industry to bisque to maturity and glaze at a lower temperature to take advantage of colour possibilities and to improve clear glaze qualities. So it’s possible to do successfully, but it requires testing to do.

The problem isn’t with glazing vitrified ware, per se. Its not testing it to see if it works and doing it deliberately vs using it to try and “fix”‘something and save time that is. 

 

edited to add: when you’re talking about functional ware, especially anything going out into the world, it is almost never worth it to repair something. Just start again. 

[Babs]

6 hours ago, Stephen said:

ouch, hope it shivered in your studio and at the customers home.

Didnt leavemy shed, well in one piece that is:-)

[CactusPots]

I wouldn't glaze an entirely unglazed pot that was high fired either.  I have though applied glaze to high fired pots to refire.  As an example, a copper red that had areas that didn't reduce properly or the glaze was too thin.  Some of the most far out pieces are multiple fired with glazes layered at each firing.