Pinhole problems

[Min]

49 minutes ago, Lbauer12 said:

I have one more question. My kiln is in my garage.  Is it ok to fire when it’s around 40 degrees outside. The thing I’d be concerned about is when I take it out if the change in temperature would damage the glaze. If I wait until it’s room temperature does it matter if it’s a little cold?

No worries on firing when it's 40F outside.

If the glaze crazes when you remove pots from the kiln it won't be because of the temperature being a little cold. It will be because the glaze is too small for the clay. Simple way to think of this is to think of a pair of jeans and how they fit. If I wear a size 10 and my daughter wears a size 4 if I put her jeans on the seams will split. If she puts my jeans on they will bag out and fall off. Tight splitting jeans is like a crazing glaze, loose falling off jeans is like shivering glaze. Crazing is far far more common than shivering. 

[Lbauer12]

That makes sense thanks. With the 02-06 clay that I have why would I experience crazing if bisquing to 04 then using 06-05 glazes?  I guess the elements are 05-6, but are some glazes just not compatible with certain clays even though it says they are?

[Min]

32 minutes ago, Lbauer12 said:

but are some glazes just not compatible with certain clays even though it says they are?

Back to the jeans analogy, CK jeans fit differently than Levis. Glaze has to fit the clay, not all glazes fit all clays.

Underfiring a glaze can be a cause of crazing. If the glaze can be fired hotter then I would suggest doing it, might help with the crazing, have to test everything with ceramics. Make up some large test tiles or pieces and try out your glazes with those rather than "real" pots. 

[Bill Kielb]

48 minutes ago, Lbauer12 said:

That makes sense thanks. With the 02-06 clay that I have why would I experience crazing if bisquing to 04 then using 06-05 glazes?  I guess the elements are 05-6, but are some glazes just not compatible with certain clays even though it says they are?

This may help, most things expand and contract with temperature. How fast and therefore how much they do that, becomes one of their finished properties. Glazes that craze generally grow slower than the clay they are applied to or the clay is growing faster than the glaze does. In effect a fit mismatch hence Min’s clothing example. We really don’t know these rates for clay and glaze until fired to their final form. So testing the clay and glaze combination is often the only way to know they reasonably match. It’s been said that getting a perfect match is extremely unlikely and some day the glaze will craze. Maybe 100-200 years from now - delayed crazing. So crazing or glaze fit is not necessarily a function of cooling something quickly but ………… large temperature swings can help reveal this mismatch. Folks often test from boiling to freezing to try and see how well they fit. So very large swings, much more than your 40 f temperature are often used to see if the delay is on the horizon or as a way to validate a decent fit. Simply testing the combination together is generally the only way to know they fit. In theory high differential testing reinforces that they fit well. 

Edited April 4 by Bill Kielb

[Lbauer12]

Interesting, I’m learning this is not a simple hobby…

[Lbauer12]

If I reglaze a piece that was fired to 05, should I refire it at 05 or 06? Most of the bowls are 1-2 more coats totally covered. 

[Bill Kielb]

1 hour ago, Lbauer12 said:

 

If I reglaze a piece that was fired to 05, should I refire it at 05 or 06? Most of the bowls are 1-2 more coats totally covered. 

 

Unfortunately I am not a reglazer. I find for cone 6 and 10 it stresses my wares a bunch and really I have very limited success. For low fire stuff, this may be very different though. Occasionally I will lowfire a cone 6 piece to change the look or add accent. I think you want to fire to whatever the glaze matures at or has been fired to and performs best at.

[Lbauer12]

Yep, thanks I just did 05 again.