Babs

What @PeterH said. Neph sye is a known bad boy in the glaze chem world. It is very high in sodium, which is why it is popular. It is also slightly soluble. Sodium is an alkaline deflocculant, which results in hard panning. The sodium slowly leaches out of the neph sye and at some indeterminate point deflocs the glaze slurry and it hard pans.
Also understand clay is the only material that can be flocculated to create a suspended glaze slurry. Materials such as feldspars or feldspathic materials (neph sye), other minerals such as whiting, etc., or frits do not respond to the alkaline or acidic conditions in the slurry to deflocculate or flocculate, respectively. Only clay responds to the deflocculation/flocculation process. A recipe with little or no clay, such as your recipe with a mere 5% EPK, needs a few additional percent of bentonite (a super clay) upon which to cause flocculation (if needed) by adding a mild acid such as epsom salts. And then after some time, the alkaline sodium leaches out of the neph sye and neutralizes whatever acidity in the slurry has been keeping the clay suspended, and boom, without warning it all falls down. The bentonite is not enough to stop this from happening. Dig it out and remix it with some epsom salts or vinegar to neutralize the excess alkalinity and restore the suspension.
As for the Magma product that folks above recommend, it does not chemically flocculate the slurry. It is an artificial gum additive that mechanically suspends the glaze solids. It is unaffected by the soluble leached sodium from the neph sye. It also has other attributes, so read the cautionary statements on the label. Otherwise, it floats bricks.
 

How long since you mixed the batch?
Did you check the Spec gravity?
No expert here but if you haven't had hard panning with these ingredients you're lucky.
No expert, but I kmow that after a time the effort you've gone to to defloc or floc will need revisiting  because the chemical reaction needs a boost.
Heat will accelerate certain chemicsl reactions but not an expert just an observer.

I decided to run a couple experiments to test some of the recipes discussed here earlier  Both were fired to cone 7.  I work at a community studio (Duluth Art Institute) and cone 7 was the next firing...I didn't want to wait for the next cone 6. Close enough.
First, I made up a batch of Min's "Base Test." (See Oct 1.) Then I took the same recipe and left out the talc but replaced the amount of silica that the talc would have provided.  In other words, I just took out the MgO.  My test tiles were Continental Clay "B Clay", bisqued to cone 08 and scribbled with a black underglaze pencil.  The difference was not dramatic, but I would say the "Base", with MgO, is more "fluxed" than the modification, without MgO. (Notice how the underglaze ran more when MgO was present.)
Then, I made up a batch of Bill Kielb's "Marcia's Matte", (See Oct 2) and added 10 and 20% of SiO2.  Once again, the results were not dramatic, but the added silica did indeed make the glaze glossier, though still somewhat matte. Notice how the scribbling on the original is a bit less black than the other two.
My conclusion is...yes, MgO can act as a flux in midrange glazes.  
I have to admit that I haven't worked with midrange glazes for quite a while. I've been working at cone 8 to 10 for the past couple of decades.  And I rarely use borates for high fire.  It just seems like cheating!
My original thinking was this: if it's so easy to make a high fire magnesium matte, how can MgO be a flux at a lower temperature?  Maybe borates are the key.  Maybe.  Where to go from here?  Surely there's no simple answer.

This thread has been resonating!
I went to post-secondary school with Engineering candidates who had: never (or hardly ever) used a caliper, dial indicator, or micrometer; never read a vernier; to stop to think which way to turn threaded fasteners; little or no layout experience; little knowledge of lubricants, bearing maintenance, belt tensioning; little or no experience with any cutting tools; had little or no soldering, brazing and welding experience ...looked to me that "it's harder" without practical experience.
Hands on! "Learn By Doing" see also Cal Poly
How nice for students to have at least One Class they like and look forward to.
How often is "that one class" Music, Theater, Art of some kind, Shop of some type, Sport?
What are those type of experiences without the crucial performance, work/wares/product/piece, material and finishing, contest/activity?
...like pottery without a kiln.

@PeterH Yes that is the model I have, thanks Peter, for the links and explanation.

And is there a community studio which could fire your students work? Linking school with a community resource , the results displayed in school foyer???
Softly softly catch the monkey!!
One comment re my boys group was how quiet the room was from the corridor  not me the dragon, but absorption of students in what they were trying to acheive. ..
@Benzine can you help

Great, you guys.
It's about development of the whole person, the brain is overloaded with info from screens and the neg. side of this is evident.
Good luck.
Run a clay session for the Staff!!

Over the years as a teacher, I have noticed several benefits to a wide range of students. There are those that take ceramics to fill a schedule, yet find that they are seduced by the feel of the clay in their hands, or the ability to visualize and create in 3 dimensions with a material that is lasting and quite durable. There are students with poor health or debilitating diseases that are unable to write for long or do other things, but the simple manipulation of the clay, and the drive to create something with such a malleable material strengthens the muscles in the hands and the arms allowing the student to write longer without tiring, and to do other things never done before. Then there are students that fill the schedule with something they underestimate, and end up finding connections to architecture and engineering, chemistry and physics, or even sculpture and fine arts or even the study of history and civilization  as influenced by ceramics. Long gone are the days of the ugly ash tray, or the misshapen mug as new art teachers have backgrounds that cover the years of the revivals in the 60's through the nineties.
However, getting an administrator to spring money for a kiln is difficult. I started with an old box shaped kiln and ended up in the end with two large L& L's with setters. Start small, work out a proposal, write up the unit for ceramics or even a proposal for a whole class. Check with NCECA for resources on classes and curriculum ideas. Peruse the internet for examples of exemplary practices in grade school ceramics. Don't give up, keep diligent. Over time you can win them over, but it takes constant harping to do it, Not every day , but at least once or twice a year.
 
best,
Pres

Hmm, this may be tough as many forms of art have latent workplace benefits as well as the social benefits listed above. I guess it  concerns me when an educator believes they know everything and no need to teach certain things or allow others to explore because they have little perceived value. Obviously ceramics in general can broaden knowledge in chemistry, geology, fire science, engineering, thermodynamics, etc….. Nothing like a finished product to help folks close the circle on knowledge.
It would be a shame to never let an architect build a model, or engineer to test a finished design, or perhaps an author only arranges words grammatically never to develop a plot or finish a story. I see this as similar to allowing one to sculpture but never fire their sculpture. (Very weird IMO)
It used to be you don’t know what you don’t know had meaning and making sure personal perception was not overly influenced by that. For educators it used to be a primary concern.  Tough argument for you though, I think I would list the simple impact of increased knowledge in traditional sciences as a starter for practical reasons.
Donald Rumsfeld mentioned a basic engineering understanding. He was lambasted in the press for it, yet it was a fundamental tenant in much of science and engineering when I was taught. If your principal thinks the quote below is nonsense, then sadly you may not be able to convince her with any argument. She already knows…….
 

Great, you guys.
It's about development of the whole person, the brain is overloaded with info from screens and the neg. side of this is evident.
Good luck.
Run a clay session for the Staff!!

Great, you guys.
It's about development of the whole person, the brain is overloaded with info from screens and the neg. side of this is evident.
Good luck.
Run a clay session for the Staff!!

Focus and Follow-through!!
Planning ahead and dealing with the unexpected.
Learning to criticize constructively.
Learning to accept criticism constructively.  
Asking “Why” and “How did this happen?”
 
 

And focus!!  It improves ones focus.  Yes, math, yes, chemistry (practical application)  yes physics.  For me it requires focus!  In these times of recognition of increasing depression among teens, clay, (functional or non functional) can be a valuable tool!  
I worked for the school district for 23 years.  If staff recognized a need or problem that should be addressed, we did not get very far.  (depended on the administrator at the time) but....if PARENTS brought up the topic and went to the administrator and possibly even the school board,  often that need was addressed.  Do you have some parents/guardians who would be willing to talk to your principal/superintendent/school board??
Roberta

Dig up some research on how art and working with three dimension art can expand a student math capabilities.  There are probably articles about the benefits of tactile arts for students.  One benefit is that it is very calming and improves their concentration.   I started my son with clay when he was 2 years old and he was playing the organ when he was 5.   He was at the top of his class in math in every grade.   High school isn't to late to improve a students mind,  it might improve their self confidence.   A student that doesn't think he or she has any special talents make a beautiful piece of art and it suddenly occurs to them that their may be something special about them.   That is what happened to me in Junior high school,  I don't know what would of happened to me if that art teacher hadn't put that ball of clay in my hand.   Denice

I’m going to tag @Pres, because he’s a retired art teacher and can speak to the technicalities better than I can.
I’m not an educator myself, but I can personally speak to the fact that working in clay taught me chemistry and physics. Glazes are high temperature redox reactions, and the practical application of that made the need stoichiometry calculations make some sense.
Clay and material knowledge are a cheap and cheerful introduction to structural engineering. It teaches observation and perseverance. It teaches planning. All of which are highly useful skills for most people.
 

Hard one, could bring it in as Design and Tech component of the curriculum. 
Depending on where you are, you may find you have to fire over the weekend...
Such a sad outlook, local schools don't even have a qualified art teacher atm because of that attitude. The pottery room and contents sold off after decades of a highly  diverse art program.
I taught a class of recalcitrant students, mostly boys. They were coming in at lunchtimes to wprk on their projects, ironically one was making fish head....bookends! All drawn out in the design books prior to start.
Have you colleagues in area where you can take images of students engagememt in the processes involved?
Could compare with other areas of curr...English without novel reading, etc
Not very helpful, keep plugging at it.
The need for folk to leave school with healthy life time leisure pursuits, during lockdown, thousands took up ceramics .Introduction at school important for giving confidence required to approach these pursuits....

Hard one, could bring it in as Design and Tech component of the curriculum. 
Depending on where you are, you may find you have to fire over the weekend...
Such a sad outlook, local schools don't even have a qualified art teacher atm because of that attitude. The pottery room and contents sold off after decades of a highly  diverse art program.
I taught a class of recalcitrant students, mostly boys. They were coming in at lunchtimes to wprk on their projects, ironically one was making fish head....bookends! All drawn out in the design books prior to start.
Have you colleagues in area where you can take images of students engagememt in the processes involved?
Could compare with other areas of curr...English without novel reading, etc
Not very helpful, keep plugging at it.
The need for folk to leave school with healthy life time leisure pursuits, during lockdown, thousands took up ceramics .Introduction at school important for giving confidence required to approach these pursuits....

Hard one, could bring it in as Design and Tech component of the curriculum. 
Depending on where you are, you may find you have to fire over the weekend...
Such a sad outlook, local schools don't even have a qualified art teacher atm because of that attitude. The pottery room and contents sold off after decades of a highly  diverse art program.
I taught a class of recalcitrant students, mostly boys. They were coming in at lunchtimes to wprk on their projects, ironically one was making fish head....bookends! All drawn out in the design books prior to start.
Have you colleagues in area where you can take images of students engagememt in the processes involved?
Could compare with other areas of curr...English without novel reading, etc
Not very helpful, keep plugging at it.
The need for folk to leave school with healthy life time leisure pursuits, during lockdown, thousands took up ceramics .Introduction at school important for giving confidence required to approach these pursuits....

Hard one, could bring it in as Design and Tech component of the curriculum. 
Depending on where you are, you may find you have to fire over the weekend...
Such a sad outlook, local schools don't even have a qualified art teacher atm because of that attitude. The pottery room and contents sold off after decades of a highly  diverse art program.
I taught a class of recalcitrant students, mostly boys. They were coming in at lunchtimes to wprk on their projects, ironically one was making fish head....bookends! All drawn out in the design books prior to start.
Have you colleagues in area where you can take images of students engagememt in the processes involved?
Could compare with other areas of curr...English without novel reading, etc
Not very helpful, keep plugging at it.
The need for folk to leave school with healthy life time leisure pursuits, during lockdown, thousands took up ceramics .Introduction at school important for giving confidence required to approach these pursuits....

So the Studio Manager where I've been working decided to go to bagged clay for most things, which means the studio clay I've been struggling with is now reserved to classes and sales to local schools.  I picked up a sample (big enough to make a fair sized bowl) of each of the 3 clays he currently has available to us and piggybacked onto his next order for 5 more.  The 3 we currently have are from Armadillo, Raku, cone 5 Porcelain, and Balcones Dark.  Until my new clay gets here I'll just be working with the porcelain.
I THREW PORCELAIN!  I threw it thick, granted, but it didn't fall down and die.  That rim is a scosh short of 1/4" thick.  Yes, I'm squashing it and going to learn to go much much thinner.
 

The Raku is just not very good for throwing as might be expected but I threw with it also.  I just realized I failed to take a picture of that, but it wasn't pretty anyway.  I turned it into a planter.  Who knows if it will survive kiln firing.  Unlike the porcelain, it is SUPER thin.  If I can get near that with porcelain it'll be a miracle LOL!  But here's a pic of a vase-like-object with the studio clay, the cracking is not thanks to sodium silicate, that's just what the clay does.  I was going for a spiral effect and that's what I got.

The Balcones Dark practically threw itself.  The walls are properly thin and even and that bowl at 9" across (and flared out that way) is twice as big as anything I could manage with the studio clay which would just slump and I couldn't pull it out anywhere near even anyway.

And here is an experiment with drippy glaze that failed largely because the kiln shut off due to a power failure and then started up again by itself so things got overfired.  That is a white glaze with blue celadon over the top.  I applied the blue celadon with a spoon to make drips down the side of the outside which I actually failed to take a picture of,  I waxed the inside so it wouldn't drip inside but didn't wax all the way down so it dripped past the wax and made dribbles in the bottom half anyway.  Then when the kiln re-fired itself, the wax was gone so we got melting celadon from the rim down into the inside of the bowl anyway.  But I like the effect, sans the overfiring, so I'll be trying that again.

So that's what I've been up to pottery-wise this past month.  I spent the whole summer either in my garden or with my grandson.  I have bushels of stuff to put up since it frosted 2 days ago.  Peas are still going and I didn't make it to the maters and peppers but I've got a ton of edible gourds and squash to put up.

Thanks so much for the input!! They make their glazes there so, I’ll ask the tech if it’s possible to bisque with the glaze on. Fingers crossed I don’t have to scrap it!

Do you know the recipe of the glazs?.just that there is a practice of once fired pots which doez just rhat, appIurs glaze to an unfured clay.  It could go into a glaze firing if it is possible to slow the glaze fire down till after 600°C. Or making sureno glaze on the base, bisque fire as usual then put through a glaze fire.
Or with mask on, sand off the glaze.

I would ask the person who fires the kilns to put it through the bisque firing as it is (with the glaze on it) then put it through the glaze firing. Saves having to do slow ramps for an entire glaze load.
Welcome to the Forum!

after many, many years of using used candles, i have learned a thing or two.  #1  do not use any added decorated candles with "snow".    toss them!!     #2, read #1.  or, you may end up with a mess spread all through the entire kiln load by the fumes.   read #1.
i find that mixing a red into the usual clear or white melted wax allows me to see exactly where the wax is and how far up the edge it goes.   i single fire nearly everything so scraping off any splashes or whatever is easy since the clay is removed with the mistake.  if done on a bisqued piece, re-bisquing removes the wax.
wiping the bottom on the interior edge of the hot pan immediately removes enough wax that the burn-out smell is hardly noticable.  my hot pan is set at 350, and i wait until it is that hot to attempt to wax bottoms.  the amount used is just enough to cover the foot.
the best part of using hot wax is that it is almost instantly dry.   some brush on wax needs hours to dry.

It will just burn out when you bisque properly. I use candle wax all the time. A local church gives me candle ends. What it has shown you is probably your poor ventilation. If the candlewax is dyed the fumes may be more toxic.