I got Snowed (glaze!)

[Pyewackette]

So that "Snow" glaze I've been talking about that is provided by the studio as either cone 6 OR cone 10 -

Turns out it is NOT cone 6 at all, only cone 10.  While the studio manager told me this and acknowledged that it is marked for both (which predates his tenure here), a studio minion stood nearby nodding.  That would be the same studio minion who told me to use it for cone 6 firing.  Note that it is the ONLY white glaze they have that was ever marked cone 6 (the other, Leech White, has always been marked cone 10 only).  Then she told her entire class last night that it is a cone 6 glaze.

So not sure what's up with that, but clearly I need to start providing my own glazes. I mean I know the manager says they're reworking the glaze line but come on.

So I have a few questions (Oh isn't that a big surprise!)

Firstly when I fired it at cone 10 it turned brown in spots and crazed on the inside of my mug.  Since multiple people have used that glaze at cone 10 reduction for years successfully I assume I may have done something to cause the crazing (although honestly the talc and some other ingredients in the clay body (and probably the glaze as well) have changed so there is that to consider as well, but lets go with "my fault" for the nonce).  What might I have done to cause or worsen that situation.  Also just FYI that glaze is SUPPOSED to turn a nice coppery brown in cone 10 reduction.  Mine didn't.  Only in spots.  May have had something to do with where it was in the kiln, I was told.

Then they keep telling me crazing in a glaze liner isn't a glaze fault, nor are pinholes.  I keep getting both.  Again, assume the fault is in myself, and not in my stars ... what could I be doing to cause that?  And they ARE faults on utilitarian ware.  I wouldn't buy a mug with pinholes or crazing, especially not in the liner glaze, and I certainly wouldn't try to sell one that way.  Am I being overly cautious?

Finally I apparently managed to glaze a piece too THINLY for a change.  It came out grey in part instead of cranberry.  The inside glazed nicely but the outside is mostly grey in lumps and swirls.  It was suggested I reglaze that piece except that's a very glossy glaze (even when its grey) and the glaze isn't sticking that well.  Is there really any point in even trying that? 

I didn't think to take pictures.  I'll try to get some Sunday (left the pieces at the studio, it'll be Sunday before I can get back there).

And lastly.  Given it seems I'm going to need to start making my own glazes - what's a nice, easy, reliable cone 6 white liner glaze that isn't too spendy, and what do I need to buy to make it?  I'll start with that since there is none to be had atm.  And yeah, I know, test tiles with the clay body.  I might need one that is as forgiving as possible given I have no control over what keeps coming out of the pugger.

*I've got the respirator fixed up. SAFETY!  Also I don't have any of the recipes for any of these troublesome glazes. I have asked and was told I could have them but ... not yet produced for my perusal.  I'm sure they're busy.  I'll poke them again in a week or so, well after end-of-classes rush is over.

[oldlady]

there is a wonderful glossy white glaze in one of my favorite pottery books.  getting into pots by george and nancy wettlaufer.  published in the 1970s.  he explains glazes and how to adjust them in a very simple way.  i use that one, named XS for extra shiny, in all my bowls and it is excellent.  very white.  my clay is little loafers from highwater.  might not be available in Nowhere.

   XS  glossy white cone 6 

soda spar  (kona f4 is what i have)       40

whiting                                                                 20

silica 325                                                             20

ball clay (C&C is what i use)                    10

zinc oxide                                                             5

total                                                                      95

for white add zircopax                                20

i always throw in 2% bentonite when i mix any glaze.    any glaze because once was enough when i did not and created a solid rock that would not stay mixed.

 

   

[Min]

23 hours ago, Pyewackette said:

Given it seems I'm going to need to start making my own glazes - what's a nice, easy, reliable cone 6 white liner glaze that isn't too spendy, and what do I need to buy to make it?  I'll start with that since there is none to be had atm.  And yeah, I know, test tiles with the clay body.  I might need one that is as forgiving as possible given I have no control over what keeps coming out of the pugger.

Asking for an easy, reliable cone 6 white liner glaze is a really broad question to ask.  What glaze works for one person doesn't necessarily mean it will work for someone else or even for the same person using two different claybodies fired to cone 6. For instance the glaze that OldLady posted above would no way fit my claybody without crazing. (20% zircopax is a lot too!) Reverse would also apply, if I gave my low expansion white glaze to OldLady it would probably be unsuitable for her claybody and would likely shiver.

I would suggest looking on glazy for ^6 white gloss recipes. When looking at the recipes look at the UMF chart at the bottom of the recipe pages. Go for ones that fall well within the white area of the Stull Chart and start mixing up small test batches. When you get a test tile that you like the glaze on mix up a slightly larger batch of about 1kg and glaze some actual small pots with it. Do some stress tests with those test tiles and small pots and see if the glaze stands up.

BTW any clear gloss glaze can be made white by adding an opacifier, zircopax is the least expensive, tin makes a less harsh white but it's expensive, can use a blend of both of them too. Another option for finding a good white is to start with a clear that fits your clay and add an opacifier.

[Hulk]

+ on clay and liner glaze quests on parallel paths; I was getting closer on a fit for a white stoneware, then went to a different white stoneware, where latest glaze fits. Lining up the tests, on clay one the craze pattern gets bigger, on clays two and three the craze pattern gets bigger, is almost gone for liner three, only where extra thick, and liner four, fit.

On looking for recipes, look at many, however, for choosing to mix up, I'd like to suggest sources that are "reputable" and include notes on usage, results, durability, testing, etc.

[Min]

1 hour ago, Hulk said:

On looking for recipes, look at many, however, for choosing to mix up, I'd like to suggest sources that are "reputable" and include notes on usage, results, durability, testing, etc.

+100

edited to add: becoming familiar with what the info on glaze calc is showing will give a lot of clues as to whether a glaze is likely to be durable or not before starting to test the actual glaze on tests.

 

[Rae Reich]

About that Cranberry Cone 10 - reds are notorious (now you know) for being ‘fugitive’. It really does depend, often, on where in the kiln as well as how thick/thin the application and, importantly, the length, intensity and duration of the reduction. You have little control of these factors in your studio, so reds are usually a happy accident. Further, the best red outcomes are frequently on the inside of the vessels where they get the most even reduction, leaving the outside anywhere from clear to snot. Some potters put a little cobalt in their reds so that where it doesn’t go red it will at least be blue.

Re-firing disappointing reds is common. Sometimes a different spot or firing conditions will do the trick. You don’t need to re-apply the glaze, just put it back in for another Cone 10 Reduction. 

[Pyewackette]

@Rae Reich Actually I failed to mention, the cranberry was fired at cone 6.  Supposedly it is a cone 6 glaze, though I look at all of these with considerable skepticism by now LOL!  So maybe I SHOULD refire at cone 10 reduction.  Can't be any uglier ... I hope.

I'm also getting real tired of the pinholes and crazing.  Its not like I think these can't be my fault.  More that I keep hearing that they are not faults at all!

[Rae Reich]

9 hours ago, Pyewackette said:

@Rae Reich Actually I failed to mention, the cranberry was fired at cone 6.  Supposedly it is a cone 6 glaze, though I look at all of these with considerable skepticism by now LOL!  So maybe I SHOULD refire at cone 10 reduction.  Can't be any uglier ... I hope.

I'm also getting real tired of the pinholes and crazing.  Its not like I think these can't be my fault.  More that I keep hearing that they are not faults at all!

Please don’t think I told you to refire a Cone 6 to Cone 10R! Refire to the original cone.

You are certainly right to think of crazing and pinholes as flaws that affect utility and salability!

Crazing is usually because the glaze doesn’t quite fit the clay. Test to find which of the available ones fit the clay. Also, if a cool draft hits the pot before it cools down enough, sometimes the glaze will shrink faster than the clay and craze.  Or, if the glaze is way too thick, sometimes.

There’s lots of info about pinholing here. Search topics. Mostly, it’s application but sometimes it’s a mistake in the firing - if you suspect the firing, check the other peoples’ work in that firing for evidence before getting too riled up  

 

 

[Pyewackette]

@Rae Reich There are a few things going on at this studio.  One is a recent changing of the guard - the old manager of decades retired recently and has been replaced.

Then there is a weird sort of studio culture, well, maybe its normal but it seems weird to me.  You have the old guard, you have the students, and you have me, who doesn't fit in much of anywhere LOL!  And there is a heirarchy in the old guard.  Not everybody's work gets fired in a timely manner.  I've experienced this myself.  But I will soon have my own kiln, albeit pretty small, so if I'm in an all-fired hurry (see what I did there?  WORDSMITH, me!) I can fire stuff at home.  BTW among the old guard there are a few artists, but mostly dabblers, some of whom haven't been actually in the studio since Covid started.  A lot of them are on "the board".  Hopefully that describes the culture I'm trying to get across without more needing to be said.

And then there is the supply stuff that everybody is experiencing.  Ingredients are either totally gone and never coming back, in short supply, back ordered forever, not the same quality, etc etc etc.  So the clay has changed, the person MAKING the clay has changed, the glazes are about to change.  And the glazes in particular, there is weirdness there as well, about who thinks they are and are not food safe and what cone they are supposed to be fired at. When I asked why glazes weren't being labelled appropriately (food safety, putative cones) I was told it would ruffle feathers (this was months ago, pre-new management).

I'm hoping that'll get straightened out this month while there is a hiatus from teaching classes.  There's a new sheriff in town LOL! Hopefully he's going to make MAJOR changes to the way the glazing studio has been run.  I know he's said he's changing the line of glazes.