Hulk

It was a safety thing -- it (understandably!) didn't like the debris in the valves.
Unpacked the kiln this morning -- beautiful firing and in the shortest firing timeframe reflecting the original manual. So happy a potter all round!

I have plenty of room, the mixer is on casters so it can be rolled out the warehouse door and it can be done outside. I'm gonna leave the tool business for someone else to handle. Think I'll just supervise 

I'm not finding any images where I can see how much room there is to work in.
Any road, wire wheels and cup brushes might serve? I've used both to restore rusted steel doors, frames, etc., driven by angle grinder, seven inch grinder (careful, that's a dangerous tool), drill motors and Dremel tool.
Be sure to wear gloves, eye protection and thick clothes against the flying wire and rust fragments! Protection against the noise and dust would be important as well...

This thread is jumping off from this one where the subject of the efficacy of magnesium as a flux in a cone 6 glaze came up and the prospect that  the magnesium alumino-silicate eutectic is unlikely to form at cone 6. It's probably best to read that thread for background before this one.
To test whether or not magnesium acts as a flux at cone 6 I'm going to run a test with the  glaze below. Purpose of the test is to see what effect the MgO has on the melt. I know the first version of it does melt well at cone 6 and results in a clear gloss glaze. For the second version I have removed the talc  (that  supplied nearly all  the magnesium). I have rebalanced the silica and alumina but left everything else the same. Testing if the removal of the talc effects the melt fluidity of the glaze. In theory the first glaze should have more fluidity if the MgO is acting as a flux.
There is 0.1 MgO left but this is as low as I can get it without messing around with the other materials. It's a bit of a wonky recipe insofar as materials used and totals as it was part of an experiment I was doing blending different recipes.
@BobMagnuson, does this look like a suitable recipe candidate for this test?
Also, if anyone has the eutectics for a boron calcium magnesium silica alumina melt that would be terrific! Or even one with boron magnesium alumina silica. I found some for boron + magnesium here.  The last column is in degrees C.

 

 

I don't use Stroke & Coat so I went ahead and emailed Mayco, their response below. How well the underglaze will show through is something you will have to test.

Vacuum when there's new bits/dust; if I'm careful, that's not often.
Sieve every time, unless I'd sieved and used the glaze within the last few weeks, and I'm sure there's no bits/chunks/things dropped in there...

There are different methods of creating a matte glaze. Some matte glazes employ more than one mechanism to do so. The mechanism and oxides used will create different types of matte, some will feel butter soft (like a good magnesium matte), others will feel dry (like one created with barium), some cutlery mark easily (often these are high alumina mattes that don't use a secondary mechanism or oxide to create the matte) and so forth. Oxides that when used in higher amounts can cause matting are magnesium, barium, strontium, titanium, zinc, calcium and alumina.
There are also underfired glazes that will be matte but this is simply because they haven't been fired hot enough to melt properly.
Slow cooling a glaze is one method of achieving a matte glaze if the glaze is high in one or more of the matting agents.  Particular oxide(s)  combine with silica and precipitate out to form a microcrystalline glaze. These micro crystals will scatter the refracted light causing a matte surface. In effect what is happening is the glaze is devitrifying as it cools.  Since these matting oxide(s) + silica micro crystals have a different composition from the remaining glaze I would argue the calculated R2O:RO flux ratio is no longer valid. 
There are exceptions to the slow cooling method of achieving a matte glaze, barium carb for example will cause a matte glaze regardless of the cooling schedule. Adding excess alumina oxide will also cause a matte as an excess of it will simply not be taken into the glaze melt. 
 

This is very helpful! Thank you! 

I  used bags that the newspaper came in,  I no longer take the paper so I just put the clay directly in it.  My extruder is homemade so I think it has more areas for the clay to hide in.    When I am finished with it I take it apart and let it soak for a day before I clean it.     Denice

Great! Thanks for the recommendations!

Hi Summerss,
Welcome to the Forum!
Could be the recommended bisque fire is 04 and the clay is fully mature at cone 6.
Can you provide identification/source of this clay?
Expect clay to become fully "closed up" - about as impervious to water as it will get, without starting to slump, melt, bloat, fizz or present any other typical overfired characteristic - at a particular cone. When fired much under the ideal cone, the clay will likely take more water, be less strong...
Some clays are more flexible that others in terms maturity range.
Some mid-range clays I've tried misbehave when fired much over cone 5; others tolerate a bit over cone 6 without issue.
That said, might be best to verify by test.
Fire the clay to 04. Is it fairly strong, does it "ring?" Does it take the glaze well - absorbs some water, but not too much?
From there, fire to target - try cone 6. Do the glazes come out smooth and shiny, no fizzy bubbles, no pinholes or other defects?
Fire some bare bars to test absorption with; weigh the fired bars, soak in water, pat dry, reweigh.
Put cones on each level. If part of your kiln fires cool, perhaps cone 5, good place to put more tests.
If cone 6 is too much, cone 5 might do.
Test!
The vendor may be able to provide some guidance.

The glaze will not adhere to Baileys or advancer shelves (kiln shelve.com) You just knock off any glaze drips and it does not affect the next pots fired
You should get a total quote from both suppliers which includes trucking /shipping before buying
in terms of washing I am an all porcelain studio and the pots  are fired to soft cone 11  and will pluck on unwashed shelves -meaning the foot will stick in small amounts sometimes. Leaving sharp bottoms .
That means for me I use a Quaility home made wash on the shelves. 50% alumina hydtrate 25% EPK and 25% calcined EPK. I thin this to cream constentancy and roll it on with a paint roller and sun dry it on sun heated shelves .
I ahve about 65 advancers and a few Bailey German shelves-they all act all the same. I have fired them a zillion times. I have broken some as well . You need to keep them dry not stacked on concrete (I use wood under them on concrete) Never blown one up . After washing them I slow bisque them with pots on them in a regular bisque fire.

Thank you fights for the quick answers! @Min I have made similar observations, the glaze that showed significant less gloss after the 6 hour boil has also been in the dishwasher almost every day for about 6 month now without any change in appearance. So I also feel like this test might just be too harsh. I wish I would have a put a regular porcelain mug from the store in too just to see how a commercially made one would hold up. 
 
@Callie Beller Diesel thanks for the warm welcome. Interesting that colorants do seem to have such a strong effect, even with good base recipes. Makes you really think that you always need to run tests even if it looks good on paper. Fingers crossed that you will be successful with the line blends. 
 
@Bill Kielb I agree that not all glazes are winners even when they look good on paper. I feel like though that maybe this test is too harsh because other glazes (variegated slate blue from mastering cone 6 glazes and a stable glossy glaze) also suffered through this test. Going more into the direction of glossy would be a good idea but I am trying to create a satin finish with the 6:1 ratio + slow cool. Thanks again for your time and Input 

Spent a huge part of summer getting ready and moving and now firing a new to me Geil 18 cubic foot downdraft kiln.
It started years ago when I found this kiln for my self and a potter fiend I know said he wanted it so I let him buy it and ship it up from LA. He fired it twice and passed away. I promised his widow to clean out his studio which I did a few years ago and this summer finally made moved the kiln (it weights about 2,700#s)
It require me knocking out some support collums and putting in two 20 foot LVL beams so I could open up my kiln area out under a huge metal roof area. Once the beams where in We moved the small 12 cubic updraft out of the way and I jackhammered out the column supports I poured in 1974. And made large cement pad -about two yards of concrete -I had a pump truck pump it into our space. I added some small wings to the main pour a few days later exposing in more rebar for the kilns to set back from one another more. I had to deconstruct a wall at kiln site in his kiln room and spent 3 days getting kiln out onto a specialized equipment trainer with a pallet jack .The trailer  jacks down flush with ground level to put kiln on and made a solid wood support structure in girl kiln (floor sides and arch support to move it the 15 miles. Here at home it landed on the street for 5 days and  derusted then painted it where it needed it and had a local yard move it with a forklift to my pad where I again used a pallet jack to fine tune it and the other kiln. Of courseI had to move my gas lines before the concrete went in and got two 1 inch line stubbed up from my 2 inch lines underground that run through my kiln area. I had to change out 15 orfices in the Geil (drilled them out with super fine drill buts) as the kiln was propane and now its low pressure natural gas. I tried to fire all three kilns at one a few weeks ago and did not have enough gas to do that but I did fire the Geil and my car kiln two days ago with no issues. I was abal to put both my peter Puggers on this slab as well and now that can move around with ease. The whole area is way more efficient now and I did I had done this 10 years ago. The Geil sips gas but now i must order 14  new 14x28 advancers as the old shelves it came with are just to thick and heavy and warped for my old body. Those shelves will cost as much as I paid for the kiln and will take 3 months to ship here from Germany (thru bailey). I am unloading my second glaze fire today from the Geil and I have bisqued in it twice as well. The auto pilot system has a few bugs but I'm working thru it.

Here's a revised Spearmint recipe that I use in my studio, and I've never had problems with it:
Gerstley Borate   11.5 Frit 3134                  5.53 Neph Sye                  4.27 Whiting                  17.58 Calcined Kaolin    8.22 EPK                           22.38 Flint                          30.53  
 
Spearmint.pdf

You run a higher risk of having blisters or pinholes unless you re-bisque to the temperature you know works. 

I'ld do it again to your usual cone once you have your kiln sorted out.

@Christy Ann, while you are doing your testing I would suggest doing some absorption tests with your claybodies also. Manufacturers post absorption figures but it's best to do your own testing since those posted figures can vary from actual results using our own kilns and firing practices. Info on how to do a calculated absorption test on this link about 2/3 the way down. Given the posted absorption figures are fairly high for the clays you are using and typically ^6 and ^10 work isn't glazed on the bottoms (like lowfire or earthenware usually is), this is relevant. As has already been said the absorption figures for functional ware at mid and high fire should be below 1 1/2 - 2%.
While you can get a well fitting non crazing glaze for pots fresh out the kiln they should still be stress tested for delayed crazing also. When functional pots (with higher absorption) is used it soaks up moisture from use and from doing the washing up. This moisture enters a porous claybody causing it to expand ever so slightly. (especially when heated as in a microwave) When the claybody expands two things happen: one is the clay can become very hot, as in too hot to pick up a mug by the handle, and secondly the glaze will more than likely craze. This is called delayed crazing. Delayed crazing can also happen over time even without using the pot if the absorption is quite high by atmospheric moisture.
edit: to stress test for delayed crazing put some samples (fired in different areas of the kiln) into a 300F oven. Leave them there for 20 minutes or so then plunge them into ice water. On a clear glaze if there is crazing it should show up, if unsure cover it with a felt pen then wipe it off. (or use calligraphy ink if you have it)

The software I'm using (Glazemaster) calculates COE 6.52 for that glaze, which, if all things were equal, would craze on some of the clays I've tried (and no longer use...), and maybe craze on one or more that I use now.
However, all things aren't equal!
My understanding is that:
  a) calculated COE is especially helpful when adjusting a recipe, where the ingredient ratios are adjusted, and/or a new ingredient is introduced;
  b) calculated COE is less helpful for comparing glazes that have radically different ingredients/recipes, where a glaze with a lower number may craze more than one with a higher number.
My own experience supports both notions.
I'd started over several times in my quest for a well-fitting clear.
The sodium and potassium were lowered, and lowered again; talc was raised, and raised again; lithium was introduced - via petalite, close, a bit more talc, a smidge more petalite, voila!'
I've posted the recipe here somewhere; if you're interested, OP, shout. No guarantee it would work with the clay in question! GlazeMaster calculates COE of 5.31

The software I'm using (Glazemaster) calculates COE 6.52 for that glaze, which, if all things were equal, would craze on some of the clays I've tried (and no longer use...), and maybe craze on one or more that I use now.
However, all things aren't equal!
My understanding is that:
  a) calculated COE is especially helpful when adjusting a recipe, where the ingredient ratios are adjusted, and/or a new ingredient is introduced;
  b) calculated COE is less helpful for comparing glazes that have radically different ingredients/recipes, where a glaze with a lower number may craze more than one with a higher number.
My own experience supports both notions.
I'd started over several times in my quest for a well-fitting clear.
The sodium and potassium were lowered, and lowered again; talc was raised, and raised again; lithium was introduced - via petalite, close, a bit more talc, a smidge more petalite, voila!'
I've posted the recipe here somewhere; if you're interested, OP, shout. No guarantee it would work with the clay in question! GlazeMaster calculates COE of 5.31

We will do some tests. Thank you so very much! This helps 

This is interesting, in that the calculated COE is low enough that I wouldn't expect it to  craze  on any of the clays I use.  Regardless, my usual fix for glazes with too high an expansion coefficient is to add a bit of talc.  I'd begin with maybe 250 g talc added to the amounts you listed as a starting point and go up from there.

I remember seeing several "iron wire and golden thread" pots in the Percival David museum years ago, and they formed a lasting impression.
A couple of weeks ago I noticed that a crackle pot that I probably made in the 1980s had developed a significant number secondary cracks. But these cracks only visible when looking hard from a foot or so.  So I've been wondering if I should stain these secondary cracks with a brown "Indian ink". Although I'm not certain that the primary cracks are bold enough to give a good end result. 
PS From p585 of Ceramic Technology by Rose Kerr and Nigel Wood (Volume 5 part 12 of https://en.wikipedia.org/wiki/Science_and_Civilisation_in_China)
Perhaps the best evidence for the contemporary appreciation of crazing in Kuan and Ko ware is the occasional practice of staining the major glaze-crackle with an intense black pigment to provide a network of fine black lines on a smooth light ground. By necessity, this would have happened soon after the firing, and most probably when the wares were still hot from the kiln, when the craze lines were relatively open. Ceramics can continue to craze for days, or even for years, after firing,and this secondary crazing system often appears as a finer network on Kuan wares, between the major crackle lines. This secondary crazing is often stained a lighter colour, perhaps deliberately or perhaps simply through use. These two crazing systems supplied the celebrated "gold thread and iron wire" effect, so often admired in Kuan and Ko wares.  How the fashion for staining the crackle began is not known,but one possibility is that it was first used as a `rescue' process, designed to improve the appearance of accidentally oxidised pieces.

I love how curious you are about so many different techniques and styles! Stain the initial primary crazing then leave the pot for the secondary craze lines to develop unstained.

Anyone tried this double crackle effect with a Guan ware type glaze (also described as Ge ware, 13th/14th century AD - China)?