Tag: Test Tile

Ceramic Materials Workshop – The Middle Glazes

                         It’s been pretty cool to watch Ceramic Materials Workshop develop into what it’s become. Matt and Rose Katz are building an amazing thing, and their list of glaze disciples pushing the envelope of glaze magic has grown steadily. I’d planned to become an initiate myself and take the October class… but life on a remote island in Southeast Alaska has it’s own demands on my time, attention, and energy. That said, I just got this info from CMW in my email, and it looks great – certainly in line with what Ceramic Action is all about. I’d encourage you to check it out, you can not go wrong. You can even use the code CMWRULES and get the whole shebang for 75$ (Less than the cost of my average bar tab)!!!

The Middle Glazes – The Story of Mid-Temperature Glazes

This self guided workshop is a comprehensive, 54 part study into Mid-Temperature glazes. Also known as Cone 6 or Cone 5-6, these glazes are one of the most popular firing temperatures in ceramics. They can be beautiful, enticing, engaging and incredibly frustrating. In this workshop we will explore in depth, what we know to make the most out of Mid-Temperature glazes. We will take the mystery of materials, formulas and firings and translate them for real working artists.

Topics we will Explore:

  • What is a glaze?
  • What is Cone 6?
  • Chemistry basics
  • Glaze chemistry
  • Materials
  • Understanding glaze formulas
  • Understanding cone 6 formulas
  • How temperature works
  • Glaze mapping (prediction)
  • Matte glazes and fake matte
  • Glaze durability
  • Converting Cone 10 glazes
  • Effects
  • Identifying Cone 6 glazes
  • Altering glazes
  • Problems with Cone 6
  • And even more!
For a limited time, get 25% off by using the coupon code: CMWRULES
Sign Up Here
Copyright © 2019 Ceramic Materials Workshop, All rights reserved.

Want to change how you receive these emails?
You can update your preferences or unsubscribe from this list.

Basalt as Colorant in Celadon Glazes

Basalt as Colorant in 2 Base Recipes.
Basalt as Colorant in 2 Base Recipes.

More local Basalt. Here used as colorant in high fire celadon glazes. On the top left, the raw material which was collected from various places throughout Idaho and Utah (and all mixed together), bottom left the homogenous, calcined, milled, sieved, and dried material ready for glaze.

In this set the basalt is supplying the iron necessary for that timeless celadon blue. Its also bringing significant additions of magnesium and calcium to the recipe. The % of basalt here ranges from 0 to 10% in 2.5% steps – applied to a dark stoneware and porcelain tiles.

This series were fired in a very fast and simple cone 10 reduction firing with a very basic reduction cool. 6 hours start to finish, in a small fiber test kiln — Heavy body redux for 30 min @ ^012-^08, then light redux to ^6, then a medium redux to ^10. At soft cone 11 I crash cooled a few hundred degrees, turned the air and gas down, dampered in, and put the kiln into about a -4°/minute cool, periodically opening the door to quickly crash cool -30 or -50 degrees until 1400, then shutting everything off. In some cases reduction cooling will effect the color and quality of the glazes significantly, but here it only effected the stoneware – keeping the iron oxide on the surface in its black reduced form. A good reduction firing will yield these glaze colors with no special effort cooling – here the RC was strictly for a darker stoneware color.

The Recipes

Fiske’s Tichane Chun
Custer Feldspar 48
Silica 31
Calcium Carb. 20
Bone Ash 1
(Iron Oxide 1.5)
— A range .5 to 3% Iron Oxide gives a similar spectrum of blue as the basalt does here – different flavors of Iron bearing materials yield different flavors of glaze, obviously. I’ve tried probably more than 50 kinds of iron over the years – try what you have and figure out what flavor you like best!

Fiske's Tichane Chun with 1.5% Red Iron Oxide. Fired to C10 in Reduction.
Fiske’s Tichane Chun with 1.5% Red Iron Oxide. Fired to C10 in Reduction.

Fiske’s (Pinnell Clear) PC Celadon
Custer Feldspar 25
Grolleg Kaolin 20
Calcium Carb. 20
Silica 35
(Spanish Iron Oxide .85)

Fiske's PC Celadon with a range of 0%-2.55 Red Iron Oxide. Fired in C10 Reduction.
Fiske’s PC Celadon with a range of 0%-2.55 Red Iron Oxide. Fired in C10 Reduction.

 

Rhyolite and Basalt Glazes

I was beyond excited to work with my newest found material, a rhyolite from Topaz Mountain, in Juab Country, Utah.  This time rather than choosing a handful of very large rock samples (to insure relative material consistency), I instead went to a wash and filled up a 5 gallon bucket with very fine material the size of course sand. My reasoning this time was that consistency is completely relative, and as long as I get materials from the same spots, it doesn’t matter – and I can grab material that has already been 99% processed for me. In the end I think this worked out, because I was able to run 5 gallons of sand through our ball mill with 2x 1 gal. ball mill jars in 10 batches. But I’m getting a bit ahead of myself, because I think it’s important to test fire a material before you go through the trouble of ball milling. So my new first step in dealing with materials (after identification of course) is to take a small chunk, put it in a small dish, and fire to cone 10 in reduction. Since this is my primary temperature range, that’s it, if there are chances I’ll also put similar samples into cone 6 oxidation as well as an oilspot firing schedule, which is about cone 12 oxidation. Here was the result at cone 10, in reduction:

wpid-2015-04-26-17.18.21.jpg.jpeg
A small rhyolite pebble after being fired to cone 10, in reduction.

 

Looks a lot like a fired chunk of granite or feldspar. Onwards with the milling!

Someone asked me about my process for ball milling, and here it is: Fill a 1 gal ball mill jar 1/3 with mixed sized media (approx 50% 1/4″ balls, 25% 1/2″ balls, 25% 1″ balls) then fill the jar with 1/2 gallon of water, then fill the the rest of the container up with material until it’s about 2/3 full.) If I had more containers I wouldn’t exceed filling the jar 1/2 way, but my circumstances are what they are, and I haven’t needed to change anything yet, such as it is.

In reduction, this rhyolite material was surprisingly similar to my ice crackle glaze. I think with very little modification (a small addition of clay, bone ash, and maybe a bit of frit) I’m nearly positive this will look and feel like a Kuan, ice crackle glaze.

Rhyolite Glaze on a high Iron clay body. Fired to cone 10 in Reduction.
Rhyolite Glaze on a high Iron clay body. Fired to cone 10 in Reduction.

Once I had all of my material milled, I let it sit overnight and then drained off the excess water, leaving me with a glaze slurry with an SPG of 1.58 (That’s 79g of material in a 50cc syringe). That’s only important if you want to know how much material you have per given volume. Since I was going to blend this with a basalt material that was also in solution, I needed this info. After taking the SPG of my basalt material, which happened to be 1.54, I did a simple line blend. On both sides are the materials by themselves, in the middle a 50/50, and on the left and right middle 25/75.

wpid-2015-04-26-17.29.08.jpg.jpeg
Rhyolite/Basalt line blend. Red stoneware (top row) and porcelaineous (bottom). Fired to cone 12, oxidation.

 

Pretty interesting results, I think. The big surprise was how sweet the 25% Basalt and 75% Rhyolite mix came out.

1 part Basalt, 3 parts Rhyolite. Fired to cone 12 oxidation.
1 part Basalt, 3 parts Rhyolite. Fired to cone 12 oxidation.

Finally, because I was looking for an oilspot/tenmoku type glaze with this research, I should also detail my firing schedule. Here’s my current Blaauw gas kiln firing schedule:

0 time_temp 00:00 5
1 time_temp 01:30 200
2 time_temp 07:00 1160
3 time_temp 01:30 1200
4 time_temp 01:00 1220
5 time_temp 02:00 1230
6 time_temp 01:15 1252
7 oxidation 80
8 time_temp 00:08 1252
9 oxidation 150
10 time_temp 00:30 1220
11 time_temp 01:30 1200
12 cooling
13 time_temp 02:00 1000
14 time_temp 02:00 800
15 time_temp 02:00 700
16 time_temp 02:00 500
17 time_temp 02:00 300
18 time_temp 02:00 50
19 time_temp 04:00 50

Blaauw kilns have the capability of firing in extremely oxidized conditions – blowing in somewhere to the tune of double the amount of air needed for complete combustion. The default, and maximum air value is 200. An neutral flame is around 100, and a smoky reduction is something like a 70.

Basically, this program fires up to cone 6 in about 9 hours, and then goes slowly up to 1252C, reduces for 8 minutes, and then goes back to oxidation, drops to 1220 over the course of 30 minutes, then drops to 1200 over the course of an hour and a half.  I’m still very much tweaking this schedule, which works very well for some glazes, and not so much for others.

Zinc Things

Zinc
Zinc

I got a lot of responses after my last post, where I made the claim that using zinc is hard on elements. I had some really interesting discussions with both John Britt and John Tilton on this subject, and I thought I’d share some of that info with you guys. Of particular interest was a tidbit from Britt where he mentioned that firing a zinc sample in oxidation leaves it unmelted (as the melting temp is 3500) while the zinc sample in reduction almost entirely goes away. Heres a fired sample from our glaze calc class, fired in cone 10 reduction. It was a thumbnail sized lump when it went in.

Zinc Oxide
Zinc Oxide

To make a long story short, the juries out on whether or not zinc directly reduces the life of kiln elements. What’s most likely is that it’s a combination of complex volatilizing compounds released during the firing coupled with high temperatures (especially if there are programmed holds). An often overlooked variable is water. It could very likely be that the extremely hard water at my current and previous studios is the culprit. If you’ve ever looked closely at old workhorse kilns, some of the deposits near the lids and spy ports are similar to calcite deposits. Its not hard to imagine Calcium and Flouride attacking the elements.

Another variable to consider is that the kilns that I’ve had access to for my entire career have been heavily used community kilns. At research universities there’s a huge range of clays and glazes that go through kilns. I’ve also heard that barium, cobalt, and copper are also hard on elements. Given all these extra variables, I suppose the only real way to quantify if and how much zinc affects elements would be to fire two brand new kilns side by side for a 100 or so firings and then compare. Let me know if you have two brand new kilns you need me to test. I’ll be happy to help you out!

On a related note, John Tilton had some great info on kiln elements. I hope he doesn’t mind me sharing the info – it seems very useful. From an email from Tilton:

The zinc thing is somewhat solved by using heavier elements. I have 11 gauge KA1s in my newest L&L, and after 104 firings they are still standing nicely. 12 gauge seems to give about 200 firings, and 13 gauge 80. Normal elements, the 16 gauge or so, give between 18 and 35 firings, not worth using. I also fire only one or two pots at a time so the total zinc load per firing is probably less than if you stacked tightly.

So it looks like 11 gauge might be the sweet spot, though they do require length to be resistant enough, and maybe that translates into coils of larger diameter.

Finally, I’ll leave you with the Material description from Digital Fire. I highly recommend consulting digital fire for material descriptions, and if you have the means, purchase access to the software. So worth it. From Digitalfire.com

Zinc Oxide

Pure Source Of Zinc

Formula: ZnO
Alternate Names: ZnO, Zincite

Oxide Analysis Formula
ZnO 100.00% 1.000
Oxide Weight 81.40
Formula Weight 81.40
Enter the formula and formula weight directly into the Insight MDT dialog (since it records materials as formulas).
Enter the analysis into an Insight recipe and enter the LOI using Override Calculated LOI (in the Calc menu). It will calculate the formula.
DENS – Density (Specific Gravity) 5.6

Zinc oxide is a fluffy white to yellow white powder having a very fine physical particle size (99.9% should pass a 325 mesh screen). It is made using one of two processes that produce different densities. The French process vaporizes and oxidizes zinc metal, the American process smelts a coal/zinc sulfide mix and oxidizes the zinc fumes.

Ceramic grades are calcined, they have a larger particle size and much lower surface area (e.g. 3 square meters per gram vs. less than 1; however 99.9% still passes 325 mesh). Calcined grades are said to produce less glaze surface defect problems (although many ceramists have used the raw grades for many years without serious issues). You can calcine zinc on your own in a bisque kiln, fire it at around 815C. Calcined zinc tends to rehydrate from atmospheric water (and get lumpy in the process, calcining a mix of zinc and kaolin produces a more workable powder). Alot of zinc is used in crystalline glazes (typically 25%), because these have no clay content, they bring out the best and worst of both the calcined and raw materials. The raw zinc suspends glazes much better (the calcined settles out much more). The raw zinc takes more water, but since the glaze can thin out over time it is better to add less than needed at mixing time and mix thoroughly. The raw zinc screens better (although it can be a challenge to get either slurry through an 80 mesh screen).

Zinc oxide is soluble in strong alkalies and acids.

It can be an active flux in smaller amounts. It generally promotes crystalline effects and matteness/softness in greater amounts. If too much is used the glaze surface can become dry and the heavily crystalline surface can present problems with cutlery marking. Other surface defects like pitting, pinholing, blistering and crawling can also occur (because its fine particle size contributes to glaze shrinkage during drying and it pulls the glaze together during fusion).

Zinc oxide is thermally stable on its own to high temperatures, however in glazes it readily dissolves and acts as a flux. Zinc oxide sublimes at 1800C but it reduces to Zn metal in reduction firing and then boils at around 900C (either causing glaze defects or volatilizing into the atmosphere; note that electric kilns with poor ventilation can have local reduction).

While it might seem that zinc would not be useful in reduction glazes, when zincless and zinc containing glazes are compared it is often clear that there is an effect (e.g. earlier melting). Thus some zinc has either remained or it has acted as a catalyst.

The use of zinc in standard glazes is limited by its price, its hostility to the development of certain colors and its tendency to make glazes more leachable in acids (although zinc itself is not considered a hazardous substance).

Zinc oxide is used in glass, frits, enamels and ferrites. Zinc oxide is also used in large quantities in the rubber and paint industries; in insulated wire, lubricants, and advanced ceramics.    Credit: Tony Hansen

Thanks to Tony, and John Tilton. Also a special thanks to John Britt for the feedback on my last post; the clarification on Feldspar (I was mistaking K200 for Minspar 200 – ignorant to the fact that K200 has been out of production for 20 years!) I’ve since edited my post on Cone 6 with this info.

Fiske ^6 Celadon

Fiske Celadon Blue
Gin&Tonic Cocktail Glasses

 

I get asked a lot about this recipe, and for good reason. It’s pretty indistinguishable from the best cone 10 recipes out there. For those purists out there, I’m referring to Pinnell Clear, Deller Chun, Cushing’s LungChun, and any number of Robert Tichane’s recipes from his book Celadon Blues. In any event, I often point people to an older post, but in the years since I mistakenly transcribed a recipe wrong and happened on the winning formula, I’ve learned quite a bit working with this glaze; Things like it working reasonably well in soda and atmospheric kilns, looking very nice from a range of cone 5 to cone 12, and readily taking most mason stains.

The Recipe

Fiske 6/10 Clear Base:

F4 (Or MinSpar) Feldspar 34.9

Whiting 12.8

Zinc Oxide 11

OM4 Ball Clay 13.8

Silica 27.5

(Pictured: Add 1.75% Robin’s Egg Blue Mason Stain)

 

Notes on materials, mixing, and application:

Feldspar:Since F4 is no longer widely available, Minspar 200 will work. Custer works as well, but the bubble matrix that really gives this glaze it’s character is different with custer, g200 (now g200hp), or nepheline syenite. Experiment first, because milage may vary. Of the ingredients, this is probably the 3rd most important.

Fluxes: Whiting and Zinc. This glaze is not kind to kiln elements. (See my post on zinc for clarification!) It’s my opinion that the relatively high % of zinc is caustic to electric kiln elements. If you must, ventilate the kiln, but expect a short life on the elements. Sometime in the near future I’ll be eliminating zinc and trying to use a frit to solve this, but until then I can only recommend firing in a gas kiln. It’s the cost of firing.

Clay: Probably the most important element of this recipe. When I was testing for cone 6 glazes, I made a mistake transcribing to a batch recipe. The result was that I had doubled the clay. After the firing I went back over the notes and realized why the glaze looked the way it did. One of the side effects of the higher clay content is that application is sometimes difficult. The higher % of clay makes thick applications crawl. To get around this I calcine 10 of the 15%.

Thus, my recipe looks like this:

Fiske 6/10 Clear Base: Minspar200 Feldspar 38, Whiting 14, Zinc Oxide 12, Calcined OM4 Ball Clay 10, OM4 Ball Clay 5, Silica 30. [H20 60%]

Silica: I use 200mesh sil-co-sil. I’ve tried 325 mesh, but it didn’t look right.

Colors/Mason Stains: I use Robin’s Egg Blue, Bermuda Green, and Canary yellow. Most colors I’ve tested, and usually 1.5-3% is pretty nice, but some take as much as 5-10%. I haven’t had much luck with purples, Pinks, and oranges, (they don’t play nice with the zinc) but honestly I’m largely done tweaking this one and haven’t tried in earnest to figure out those other colors.   Metallic oxides will also work, cobalt at like .3% for a not overpowered blue color.

Application: Can’t stress this enough. It’s gotta be thick. I tell people to glaze “Thicker than you think thick is, and then just a little thicker.” I’ve taken to adding just a touch of deflocculent to the glaze batch so that it needs less water to become liquid. I then add a bit of Epsom salt to thicken the batch up. Again, this is to taste. Dipping is absolutely the way to go with this one, but I’ve gotten accustomed to spraying it. Usually takes about 15 minutes to spray glaze something appropriately.

Firing: As I mentioned earlier, it’s got a pretty wide range. It will be fully melted, albeit slightly pin holed at cone 5. Ideally, I like to go to a perfect 6, but taking it to 7 or programming a hold in the schedule makes for some nice movement that suits carving and texture very well. Most of my work is completely smooth, so I prefer it to stay thick and not run down too much. It takes some getting used to, but when you do, it behaves very predictably. It can also go into reduction, but the colors change quite a bit. Less change with Bermuda Green, but quite a bit with the Robin Egg Blue. Its been fired every which way, and needs to be tested before full comittment.

Rainbow Iridescent OilSpot Glazes

Hello Again! It’s been quite some time since my last post. Gotta thank those of you who have contacted me with interest and suggestions! With so many summer projects and school stuff, it’s been very difficult to put my full efforts into any one thing… but life is what happens while you’re making plans.  Anyways, enough with the excuses.

Over the summer I had the time and energy to figure out an acceptable firing schedule in our new Blaauw kilns.  For as much as I love their sleek and sexy design, computer controllers, and top of the line hardware… you can’t look in the damn things while they’re firing. This poses several challenges for control freak oil spotters. Usually, the idea is to firein complete and total oxidation, going slowly through cone 7,8,and 9 to allow thermally reducing iron to bubble up through the glaze and cause the surface to crater or foam. By carefully monitoring the situation inside the kiln, and by pulling out glazed pull rings, the firer can increase the temperature slowly and fire until the glazes have significantly ‘healed over’. This isn’t really an option, so as a result a much more empirical approach was needed to find a good fit.

After 5 firings, I settled on a more or less acceptable firing schedule (the way this programming works is that the kiln starts at 0, take 1:30 to get to 200C, then 2:30 to get to 700C, etc). In Celcius;

time_temp 00:00 5

time_temp 01:30 200

time_temp 02:30 700

time_temp 03:00 1115

time_temp 02:00 1190

time_temp 02:30 1230

time_temp 02:30 1253

cooling

time_temp 02:00 1000

time_temp 02:00 500

time_temp 02:00 300

time_temp 02:00 50

time_temp 04:00 50

 

Once that was established, I began with some of my favorite tiles from my initial 2 rounds of oilspot base glaze recipes. My favorites:

 

NoCo OS:  (NC)

Dolomite 4.4

Whiting 4.4

K200 Feldspar 57.3

EPK 9.7

200m Silica 24.2

Spanish FeOx  10

 

Candace Black:  (CB)

Dolomite          5

Whiting           5

K200 Feldspar 60

EPK                       5

200m Silica  20

Spanish FeOx  8

Cobalt Carb       5

 

Loganspot: (LS)

Local Black Dolomite 10

K200        65

EPK          5

Silica     20

Cobalt      5

Red Iron  8

 

Fake Mashiko: (FM)

K200  37.6

Silica  9

Redart  8

Calcined Redart 35

Wollastonite   5.7

Talc    4.3

Bone Ash  .5

Red Iron   4

 

With these base glazes I began mixing, blending, and layering, and combining glazes with dipped, poured, and sprayed application.  On a whim I decided to experiment with some of my manganese saturate glazes, and that’s when things started to get really interesting. There is admittedly one glaze in particular that I’m not sharing, but with a little diligence and some wet blending, a seriously motivated glaze experimenter can discover this glaze by  looking at my old posting on my OSII series. Blend them all in 50/50 proportions and you’ll get the elusive but beautiful  GF glaze. Hell, it might even be on my blog somewhere. That’s all I’m saying for now – I’d hate to rob anyone of the learning experience… Hah! =)

 

Recently I was contacted by the British potter Allen Richards who has done some pretty extensive research into lustrous gold glazes. He suggested that I try small additions of Vanadium Pentoxide. These glazes feature 2 amended manganese saturate glazes in combinations with the usual oilspot suspects.

 

 

 

 

Here are some videos of some of my latest results. None of these particular tiles have Vanadium pentoxide.  As time goes by I’ll try to annotate the combinations MS corresponds to Manganese Saturate.

 

 

Iridescent Hare’s Fur Tenmoku

Telluride via Moab

Jeepster parked next to a clay bank with Mount Telluride in the background.
Jeepster parked next to a clay bank with Mount Telluride in the background.

 

 Back in the studio after a great trip over to Telluride, CO via Moab, UT. You better believe I scooped up some of this clay, ball-milled it, and made a slip. I also packed the jeep with a load of rocks and shit.  More on that as the story develops!

 

Red Siltstone and Clay, Telluride, CO
Red Siltstone and Clay, Telluride, CO
The San Juan Rocky Mountains.
The San Juan Rocky Mountains.
Moab Red Rocks
Moab Red Rocks

New Pots, New Recipes

#6, #5, #4 Manganese Saturate Crystalline Glazes
#6, #5, #4
Manganese Saturate Crystalline Glazes

#4 Recipe & Schedule

Fisker Bronze
Custer Feldspar.............     57.000  
  Alberta Slip................    7.000  
  Sil-co-sil..................    2.500  
  F-4 Feldspar................    1.500  
  Calcium Carbonate...........    0.500  
  Dolomite....................    0.500  
  OM #4 Ball Clay.............    2.000  
  MnO.........................   23.000  
  Copper Carbonate............    5.500  
  Iron Oxide Red..............    0.500  
                              =========
                                100.000

  Oxide   Formula  Analysis    Molar%
  CaO      0.043*   1.129%w   1.376%m
  MgO      0.019*   0.348%w   0.590%m
  K2O      0.143*   6.237%w   4.528%m
  Na2O     0.071*   2.052%w   2.264%m
  P2O5     0.000*   0.007%w   0.003%m
  TiO2     0.001    0.055%w   0.047%m
  Al2O3    0.252   11.952%w   8.013%m
  SiO2     1.783   49.756%w  56.619%m
  CuO      0.099    3.670%w   3.156%m
  Fe2O3    0.013    0.955%w   0.408%m
  MnO      0.724*  23.839%w  22.995%m

                        Cost:   0.273
              Calculated LOI:   3.521
                 Imposed LOI:        
                       Si:Al:   7.066
                      SiB:Al:   7.066
           Thermal Expansion:   6.848

Fired in Blaauw Reduction Schedule (in Celcius):

time_temp 00:00 5
time_temp 00:54 140
time_temp 01:12 260
time_temp 01:10 550
time_temp 00:30 600
time_temp 01:12 900
oxidation 83
time_temp 00:45 900
oxidation 93
time_temp 03:06 1210
oxidation 98
time_temp 01:24 1270
cooling
time_temp 02:15 1000
time_temp 01:00 900
time_temp 02:00 500
time_temp 01:00 300
time_temp 02:30 50
time_temp 04:00 50

#5 Recipe & Schedule

  Nepheline Syenite...........   65.500  
  MnO.........................   22.000  
  Silica......................   12.500  
                              =========
                                100.000

  Oxide   Formula  Analysis    Molar%
  CaO      0.018*   0.465%w   0.559%m
  MgO      0.004*   0.067%w   0.112%m
  K2O      0.071*   3.036%w   2.175%m
  Na2O     0.228*   6.461%w   7.033%m
  Al2O3    0.330   15.361%w  10.163%m
  SiO2     1.913   52.523%w  58.975%m
  Fe2O3    0.001    0.072%w   0.030%m
  MnO      0.680*  22.014%w  20.953%m

                        Cost:   0.312
              Calculated LOI:   0.065
                 Imposed LOI:        
                       Si:Al:   5.803
                      SiB:Al:   5.803
           Thermal Expansion:   7.492
              Formula Weight: 218.874

Strike Reduction Hold Firing Schedule 
in Small Test Gas Kiln in F

3:30 -> 1500F (^012)
Body Reduction
1:00 -> 1700F (^04)
Adjust to Moderate reduction, fast climb
3:30 -> 2300F (^9 flat, ^10 down)
Crash Cool
0:15 -> 1840F
Cut secondary air, minimize primary air, damp in, gas low to strong reduction and stalled holding temp
3:00 -> 1840F (Hold)
Off, Natural Cool
6:00 -> 300F

#6 Recipe & Firing Schedule

  Custer Feldspar.............   69.000  
  OM #4 Ball Clay.............    1.500  
  MnO.........................   27.500  
  Granular Manganese..........    2.000  
                              =========
                                100.000

  Oxide   Formula  Analysis    Molar%
  CaO      0.007*   0.210%w   0.256%m
  MgO      0.000*   0.006%w   0.010%m
  K2O      0.140*   6.961%w   5.057%m
  Na2O     0.064*   2.091%w   2.308%m
  TiO2     0.000    0.018%w   0.016%m
  Al2O3    0.226   12.223%w   8.201%m
  SiO2     1.533   48.751%w  55.512%m
  Fe2O3    0.001    0.123%w   0.053%m
  MnO      0.789*  29.617%w  28.588%m

                        Cost:   0.297
              Calculated LOI:        
                 Imposed LOI:        
                       Si:Al:   6.769
                      SiB:Al:   6.769
           Thermal Expansion:   7.120

Fired in Blaauw Reduction Schedule (in Celcius):

time_temp 00:00 5
time_temp 00:54 140
time_temp 01:12 260
time_temp 01:10 550
time_temp 00:30 600
time_temp 01:12 900
oxidation 83
time_temp 00:45 900
oxidation 93
time_temp 03:06 1210
oxidation 98
time_temp 01:24 1270
cooling
time_temp 02:15 1000
time_temp 01:00 900
time_temp 02:00 500
time_temp 01:00 300
time_temp 02:30 50
time_temp 04:00 50

Raw Materials in Cone 10 Reduction

From Utah State University Ceramics Technology Glaze Calculation Class.

Thanks to Shasta Kruger for Photographing, Editing, and Compiling These Images!!!!