PeterH

I've no experience in this area, but your problems might be to do with allowing time for crystal growth rather than reaching "maturity".
Just a standard reference to slow cooling in an electric kiln, to emphasise sometimes changes in appearance are controlled more by the cooling cycle than by the peak temperature. Which may require down-firing in a kiln that cools too rapidly for that glaze/effect.

Super Cool! Slow Cooling in an Electric Kiln
https://ceramicartsnetwork.org/daily/article/Super-Cool-Slow-Cooling-in-an-Electric-Kiln
 

+1
After a little googling, this looks similar:
https://www.thepostsupply.com/products/vase-no-8
I got largest image I could access from that page by opening this image into another window -- then clicking on it to enlarge it further.
https://www.thepostsupply.com/cdn/shop/files/AnemoneVaseno.8_Red_1024x1024@2x.jpg
 
Similar treatment for this one.
https://www.thepostsupply.com/cdn/shop/files/AnemoneVaseno.8_main_1024x1024@2x.jpg

 

I rhink you inadvertently did a reduction firing. Easy to do in a small gas kiln.
Do you have time to refire one as a test making sure you have a  fully oxidised atmosphere? With that amount of copper I could get black pots without trying in my gas kiln if not careful re atmosphere.

Super hard for me to see the pics are small to my eyes but looks like it could just me as simple as brushing on a white matte glaze unevenly/thin/thick and maybe a brushed cobalt wash? Could be underglaze but seems more like a wash from afar. 

Hello glaze makers! I have a very niche issue and thought someone here maybe able to help me.   I was commissioned to make a series of 8 large bespoke ceramic pitchers in a specific colour. They are to be presented as awards at a commemorative event on Dec 10. My customer selected a soft green finish from one of my existing pieces that was glazed in a traditional oribe glaze and fired in oxidation in a wood kiln ( in a group fire in Gunderoo NSW) I have a small Port-o-Kiln and assumed I could replicate the green colour by using the exact glaze (same original batch) and firing to cone 9-10 in oxidation in gas. When I opened the kiln this morning all were BLACK!!   I am not sure why. Its either because I didn't go high enough - I found out the group Gunderoo wood fire went to cone 12-13. Or because it Port-O-Kilns cool quickly and when you look up oribe on Wikipedia there is a section that says Black Oribe is achieved with a rapid cool down. Either way I have to urgently refire existing pieces to cone 12-13 or remake all agin which is a ton of work. Does anyone have any understanding of the chemistry behind this? Could I refire to higher temp and the glaze continue to mature and achieve the green colour? Any advice or insight is greatly appreciated.     RECIPE Potash Feldspar 60 Wood Ash 20 Whiting 10 Ball clay (clay ceram ) 10 Bentonite 1 or 2% Copper carb 7.5    

Mason puts out a Reference Chart that lists all the ingredients in each of their stains. 
https://www.masoncolor.com/reference-guide

Drifting off topic ...
I'm starting to get confused, because there are two ways of measuring the density of powders.
Bulk density is the weight of the powder divided by the volume it occupies (that's both the volume of the particles and any entrapped air).
Obviously this can be influenced how the powder is handled before the measurement.


Particle density is the weight of the powder divided by the volume of the particles. This volume can be measured by adding the powder to a liquid and observing change of volume. [The liquid must obviously wet the powder well.]
I'd always sort of assumed that heavy & light ZnO differed in bulk density rather than particle density.
Can anyone clarify things?
BTW references to light and heavy ZnO seem thin on the ground. But this supplier seems to be offering 98% pure heavy ZnO. Which suggests that "heavy" doesn't relate to density variations due to contamination with other elements (but may relate to the production process used.)  The listed "density" for this "heavy" ZnO is 5.606, wiki gives 5.6 for ZnO.
https://ie.vwr.com/store/product/787678/zinc-oxide-heavy-98
PS An earlier glazenerd posting describing the two processes in more detail.
 

I assume that you are making moulds for slip casting (this limits the choice of release agents).
Any idea what your masters will be made of?
Are you intending to make drop-out or multi-part moulds?
A picture of your master would give an idea if you are going to have to worry about undercuts.
PS Somebody will probably move your post, as it will get a better audience in Mold Making and Slip Casting

Thanks Peter all makes sense and it’s done well to last as long as it has considering it’s just a piece of metal bending!  I think maybe me increasing the spec of my elements has bitten me here as previously the regulator would have been turned to max much earlier in the firing but now I have to hold at 60% for several hours to keep the temperature from sky rocketing - that’s a lot more clicks than its used to! 
 
I had previously considered buying a “plug and play” pid controller but got put off by not understanding how it all works, now I’m thinking my regulator on full and allowing a plug and play box SSR to regulate might be a good option now. 
 
or a new kiln……

From https://community.ceramicartsdaily.org/topic/1557-gold-lustre-and-alkaline-glaze/?do=findComment&comment=10521
1. Lustre is a thin film of metal deposited on the surface of a fired glaze.
It is NOT a glaze in itself. It relies on the glaze interaction with the lustre for adherence and this can be anywhere between 720.C-820.C depending on the hardness of the glaze. Earthenware glazes are usually refired between 720-750.C while stoneware and porcelain usually refire between 780-820.C but that is not set in stone. Every glaze is different and you would have to test to find the common denominator for your glazes. Glass, depending on the type, starts to accept lustre from 600.c onwards. You will know if you haven't fired high enough as the lustre will rub off. If fired too high it will start to burn off and be patchy. Commercial porcelain blanks can be tricky to find the optimum temperature as a lot of these follow the procedure of high fired bisque with a low fired glaze. This appears to be the same with bone china. It takes on the characteristics of the glaze it is on. If the the glaze is very glossy then the metallic layer is very glossy. If the glaze is matt then the metal layer is matt and this then follows on for all the permutations in between. However I have noticed in my own work that copper glazes seem to be more problematic as my lustres always seem duller. This then brings me to the second point. PS
These lustres (there are reduction lustres as well) are based on resinates, which are metallic soaps. When they are heated they decompose to metal atoms and various gases such as CO2. Why most of them (e.g. copper) don't decompose to the oxide is complex, and apparently relates to the electron distribution within the resinate ion during its decomposition. Which is why resinates are still used.
Danger of skin contact & fumes until they are fully fired, then you've got a metallic thin film (somewhat amalgamated with the surface of the underlying glaze). Some of the dangers are inherent to the resinate, others relate to the solvents used.
Johanna DeMaine
Lustre Ceramics Monthly
Health & Safety and Overglaze
Background Overglaze: Challenging the Myths
 

This might give you a better idea of some of the issues involved in getting the deflocculation right.

Determining Dispersant Additions for Casting Slips
https://static1.squarespace.com/static/527ac372e4b0d4e47bb0e554/t/527fd7f1e4b0c046bfa9b90d/1384110065234/Dispersant+Addition+Procedures.pdf

If you do an absorption test on your clay it will tell you this. It's a good idea to test a claybody for absorption using your kiln and firing methods rather than what a clay manufacturer publishes it as. For functional ware below 1 - 1.5% is usually good. Link here on testing absorption if you need it. If the clay isn't porous for all intents and purposes and you run your pots through the dishwasher I wouldn't worry about the odd pinhole. Aesthetics are a different point, a pinhole on a pristine porcelain piece is going to stand out far more than one on a rustic piece. 
Ryan Coppage article here discussing bacteria growth on crazed glazes. Conclusion is if your clay is vitrified and the pots run through a dishwasher bacteria is not an issue. (article is behind a paywall but you can access 3 free articles a month) I haven't come across any literature proving pinholes harbour more bacteria than craze lines.

From https://community.ceramicartsdaily.org/topic/1557-gold-lustre-and-alkaline-glaze/?do=findComment&comment=10521
1. Lustre is a thin film of metal deposited on the surface of a fired glaze.
It is NOT a glaze in itself. It relies on the glaze interaction with the lustre for adherence and this can be anywhere between 720.C-820.C depending on the hardness of the glaze. Earthenware glazes are usually refired between 720-750.C while stoneware and porcelain usually refire between 780-820.C but that is not set in stone. Every glaze is different and you would have to test to find the common denominator for your glazes. Glass, depending on the type, starts to accept lustre from 600.c onwards. You will know if you haven't fired high enough as the lustre will rub off. If fired too high it will start to burn off and be patchy. Commercial porcelain blanks can be tricky to find the optimum temperature as a lot of these follow the procedure of high fired bisque with a low fired glaze. This appears to be the same with bone china. It takes on the characteristics of the glaze it is on. If the the glaze is very glossy then the metallic layer is very glossy. If the glaze is matt then the metal layer is matt and this then follows on for all the permutations in between. However I have noticed in my own work that copper glazes seem to be more problematic as my lustres always seem duller. This then brings me to the second point. PS
These lustres (there are reduction lustres as well) are based on resinates, which are metallic soaps. When they are heated they decompose to metal atoms and various gases such as CO2. Why most of them (e.g. copper) don't decompose to the oxide is complex, and apparently relates to the electron distribution within the resinate ion during its decomposition. Which is why resinates are still used.
Danger of skin contact & fumes until they are fully fired, then you've got a metallic thin film (somewhat amalgamated with the surface of the underlying glaze). Some of the dangers are inherent to the resinate, others relate to the solvents used.
Johanna DeMaine
Lustre Ceramics Monthly
Health & Safety and Overglaze
Background Overglaze: Challenging the Myths
 

From https://community.ceramicartsdaily.org/topic/1557-gold-lustre-and-alkaline-glaze/?do=findComment&comment=10521
1. Lustre is a thin film of metal deposited on the surface of a fired glaze.
It is NOT a glaze in itself. It relies on the glaze interaction with the lustre for adherence and this can be anywhere between 720.C-820.C depending on the hardness of the glaze. Earthenware glazes are usually refired between 720-750.C while stoneware and porcelain usually refire between 780-820.C but that is not set in stone. Every glaze is different and you would have to test to find the common denominator for your glazes. Glass, depending on the type, starts to accept lustre from 600.c onwards. You will know if you haven't fired high enough as the lustre will rub off. If fired too high it will start to burn off and be patchy. Commercial porcelain blanks can be tricky to find the optimum temperature as a lot of these follow the procedure of high fired bisque with a low fired glaze. This appears to be the same with bone china. It takes on the characteristics of the glaze it is on. If the the glaze is very glossy then the metallic layer is very glossy. If the glaze is matt then the metal layer is matt and this then follows on for all the permutations in between. However I have noticed in my own work that copper glazes seem to be more problematic as my lustres always seem duller. This then brings me to the second point. PS
These lustres (there are reduction lustres as well) are based on resinates, which are metallic soaps. When they are heated they decompose to metal atoms and various gases such as CO2. Why most of them (e.g. copper) don't decompose to the oxide is complex, and apparently relates to the electron distribution within the resinate ion during its decomposition. Which is why resinates are still used.
Danger of skin contact & fumes until they are fully fired, then you've got a metallic thin film (somewhat amalgamated with the surface of the underlying glaze). Some of the dangers are inherent to the resinate, others relate to the solvents used.
Johanna DeMaine
Lustre Ceramics Monthly
Health & Safety and Overglaze
Background Overglaze: Challenging the Myths
 

This might give you a better idea of some of the issues involved in getting the deflocculation right.

Determining Dispersant Additions for Casting Slips
https://static1.squarespace.com/static/527ac372e4b0d4e47bb0e554/t/527fd7f1e4b0c046bfa9b90d/1384110065234/Dispersant+Addition+Procedures.pdf

This might give you a better idea of some of the issues involved in getting the deflocculation right.

Determining Dispersant Additions for Casting Slips
https://static1.squarespace.com/static/527ac372e4b0d4e47bb0e554/t/527fd7f1e4b0c046bfa9b90d/1384110065234/Dispersant+Addition+Procedures.pdf

Looks like one man's collection of other folk's glazes, prob no text book as such
Some are Bwenard Leach's , some are Val Cushings , you say they are your professor's so why not ask him?

my thoughts
Renewing the wiring harness is a great idea. Making your own great too, but high quality crimp and crimp work is key. If you make your own, please buy a decent locking crimper and good quality welded seam crimps, else the premade harnesses likely a best choice. When I rewire, I use #12 and #10 MG (mica glass) rated wire good to 450c all in an overkill fashion so I can identify with make it better.
Low voltage harness
The current low voltage harness likely is ok and should currently experience less than 1/2 amp of load …….. but 18 gauge stranded is plenty sufficient. You should be able to read the side of the existing wire harness to determine what gauge and what temperature it is rated at. Again the crimp work is the important part with respect to longevity and kiln manufactures rarely seem to use high temp insulation on these.
Again I strongly suggest Measuring the resistance at these element circuits ….. at the relay, would definitely be helpful, possibly for knowledge useful by others but now will also give you a real idea of how much over designed you would want to pursue by knowing your current amperage and looking in an open air amoacity of wire table. Lots of tables here is one https://up.codes/s/ampacities-of-single-insulated-conductors-in-free-air
Since you are exploring rewiring general insulation and it’s typical ratings in order of temperature tolerance:
Mg (Mica Glass) - 450c Teflon products - 200c - 250c (fep, etfe, pef,    And others with f in them) Silicone Products 150c-200c  (srg, srk, smrl - silicone motor lead developed for small motors vibration and temperature) All the above though generally is a decent reason to just buy a premade harness that fits perfectly though. Most wiring begins to fail at their connections which overheat, anneal the copper and continue to overheat more as the conductivity decreases. The physics says this will decrease the electric load on the relays, but a harness that overheats also adds heat to an already confined space. The latter being bad for the relays as well so replacing a harness not a bad thing, replacing with a better harness, even better, but does take some diligent work, good crimps and good crimpers to achieve this.
Airflow and cooling helps everything regardless of gauge and insulation, so making sure there are no obstructions or the kiln is not enclosed in an overheated area with no way to get relatively cool air is a no cost best practice for all the electrical components inside. The control box depends heavily on stack effect which means relatively cool room air can freely flow from bottom to top and out of the louvers.

@NancyE, sorry for the late reply, I was away for a bit.
Since the beginning of this year I've had problems with 2 different claybodies from 2 different manufacturers. First issue was bits of metal in the clay which doesn't sound like your issue. Second problem was with a claybody that included small chunks of rock which sounds like it might be the same issue you are finding. This clay was from Tacoma Clay Art Center and the clay tech and I had several productive emails back and forth about it. Image below of a couple of the small chunks of rock I dug out of the clay. Is this similar to what you found?
Rae (clay tech at Tacoma Clay Art Center) and I both ran sieve tests on it and found chunks like this. Rae let me know they are having troubles with all their claybodies that contain Lincoln 60, to the point that they are running QC tests on all the new batches of it. She ran samples through a 60 mesh sieve and 4% of it didn't pass through. I would ask Aardvark if the Black Mountain contains Lincoln 60, might be a place to start.

+1
PS If you find the connectivity better with a phone it might be worth looking at phone lens adapters to give you a slightly longer focal length.
Maybe a photographer here can recommend the best camera-subject distance and focal length for these demos.

+1
PS If you find the connectivity better with a phone it might be worth looking at phone lens adapters to give you a slightly longer focal length.
Maybe a photographer here can recommend the best camera-subject distance and focal length for these demos.

+1 for the cell phone. It has the advantage of being probably already in your possession, and small tripods that are easy to position  are readily available online or at some mall kiosks. 
If you do elect to use a portrait orientation, a trick to avoid distortion is to hold it upside down. Most people will angle their cellphone forward when taking images, and we don’t notice any angle weirdness because that’s how we ourselves are viewing the world. When the angle goes the other way, the distortion is more noticeable in the moment, and easier to correct. 

I believe that you could set up a live feed with most any older camcorder or a recent digital using ports in the TV connected to the USB post in the camera. Does the TV have a model make and model # where you could look up the manual online if you don't have it?
 
best,
Pres

The reason I asked for your firing schedule is I suspect a technical nuance is at play here. Cones deal in heatwork - time and temperature. Nothing new with that idea. If the ramp rate in the final 2 hours is aggressive (relative to the Orton table, which depending on who you ask, what book you read, or what kiln controller you have, medium speed to cone 6 is 120F/hr to 2232F), the cone bends at a higher final temperature, and vice versa, a slower ramp will bend the cone at a lower temperature. Nothing new with that idea either. Your ramp 5 is set for 200F/hr to 2200F, which is pretty aggressive. Putting that into the Orton cone calculation spreadsheet, that would give you a cone 5.5, and even the 20 minute hold doesn't quite get to 6. However, the nuance that isn't always seen is that as the elements wear with usage, the actual ramp rate attained by the worn elements falters (and in the most extreme case, simply can't heat the kiln in the final segment and the controller errors out). While the cone-fire programs in the Bartlett and Orton controllers have an adaptive feature that monitors the actual final ramp rate and adjusts the target temperature to produce a good cone bend, the custom ramp hold programs do not have that capability. In ramp hold, the controller will keep chugging until the programmed temperature is reached regardless of how long that might take (unless it determines the rate is futile and it errors out). As the elements wear, the final ramp rate slows down and the cone should bend at a lower temperature, but the controller keeps going until the programmed temperature, and now the cone is overfired. Going back to the Orton spreadsheet, a ramp of 100F/hr to 2200 with a 20 minute hold should give you a cone 7, which it did. So, my suspicion is that your elements are wearing out, the programmed 200F/hr final ramp rate is bovine droppings, it's actually only making 100F/hr, and from here, it will get worse. Check the resistance of the elements and be ready to replace them as they drop too far out of spec. In the short term, drop you final temperature to 2185F and that should give you a nice cone 6 when the kiln is chugging along at the best it can do.

,)

Try "benchtop buffer" or somewhat like for a search string, e.g.

There are several sizes, powers, options "out there!"
The unit should be securely fastened (unlike the image above!), and, And, careful be, against any wrap up scenarios, also pinch points...