Electrifying

I haven't posted in a while, and for a couple of reasons.

1. I've been swamped with school work in my final term at EOU trying to grind out my BS in Accounting.

B. I've been with out a kiln for a couple of months now since my switch burned out.

and 3 I've had a hell of a time with my kilns lately in general, I pulled a second kiln I'd been storing into action and it's switch burned out as well. Not to mention the whole exploding relay incident where I connected a control box and solid state relay improperly making a bomb out of my new digital kiln controller. Fun times!

Well the good news is I've had excellent luck with the glaze recipes from Ron Roy's book Mastering Cone 6 glazes. Already got a few of them through the kilns before the a fore mentioned incidents and they worked exactly like they did in the book. Can't recommend enough Ron Roy's book, it's changed the way I feel about electric cone 6 firing. I'd been looking forward to building a reduction salt kiln for about two years now, and it all the sudden dawned on me that if I started doing once fire salt again, I'd miss the great glazes I have now. Wow, I can't believe I actually like electric firing, who'd have thunk it. Thanks Ron Roy and John Hesselberth for your outstanding contributions to the world of ceramics.

If you have an electric kiln and you don't own this book, I urge you to buy it. Probably the best 50 bucks I spent last year.

http://www.amazon.com/Mastering-Cone-Glazes-Durability-Aesthetics/dp/0973006307

Matte Black

Well I took a gamble on the matte black in the Electric Kiln Ceramics book. I got a few pots in the little kiln, two decent sized vases and an oval serving dish. The big deal for me is that I'm not liking the cone 6 firings. I should say the 818P isn't liking the cone 6. The envirovent slows down the cone 6 firings to a two day process no matter what I do. My only recourse is to fire with out the envirovent on. This time I tired to do that, but the red earthenware was gassing off so badly I couldn't see my witness cones. I decided to just pop it on for a second to clear it just to check the cones. I cleaned out the atmosphere at the end real well for a soak of 50 minutes. It was really a slow cool though as the kiln began to cool off slowly with the dials set to low. Can't wait to see if I've got a glaze that I like. I'm kicking myself for not putting at least one of the iron red samples in this load. Oh well, next time.

Fall

I've not had much to say this fall because I've not been able to work in the studio much at all. I'm finally on Christmas break from EOU and I'm back on the horse. Threw a few mugs today and have resolved to design a new mug form since I'm not impressed with anything I've made today. I pulled out the sodium silicate to make some crackle slip mugs. I did a few and had some fun, but I my slip was a bit thin so I couldn't get a nice brush mark out of my coarse hair brushes. The crackle is only slightly interesting and isn't at all what I was looking for. I resigned to make one more mug with just brush marks and no crackle. Tomorrow I'll make and assemble a mug. I'll post a picture if something of note comes from my effort.

Research

It seems I'm always doing research. I've been reading a lot about matte glazes, in trying to get something in a cone 6 matte. I've run into a clay club blog with some good glazes on it. It's amazing how you know when you find good websites or blogs, and then you run across them referenced on other websites and blogs. In this spirit here are some links I find fascinating.

http://www.patrickhorsley.com/

http://www.kazegamas.com/index.htm

http://ncclayclub.blogspot.com/

Etsy

You can now see on the right side of my blog a gallery listing from my Etsy store where my pots can be viewed and purchased. If you would like more information, or to put in a special order request please email me at potterpdx@yahoo.com and put "BenCo pottery questions "BenCo pottery special order" in the subject field.

Glaze Research

Digital Fire has a lot of free links that hold a wealth of information. You can find chemical data on nearly all individual materials, as well as a number of formulated glaze recipes. What I've been working on the last week is trying to figure out proper formulations for durable matte glazes in both Cone 1 and Cone 6. I have found a myriad of recipes for high gerstley borate matte glazes. Which I know from first hand experience from testing in college that these glazes are not durable and they leach. So I'm trying to come up with a formula made from the materials I have on hand that make a matte glaze. The good news is I've found shiny base glazes for both the cone 1 and the cone 6. I've also found some proven cone 1 and cone 6 macro crystalline glazes. I have a lot of testing to do now that I've done some research. However for anyone who might be interested in these types of glazes here are some links to digital fire that might help.

http://digitalfire.us/4sight/education/g1214w_cone_6_transparent_base_glaze_121.html

http://digitalfire.us/4sight/education/g1214z_cone_6_matte_base_glaze_122.html

http://digitalfire.us/4sight/education/formulating_ash_and_native-material_glazes_188.html

All three of these links are great. The last one is of particular interest because I have an ash deposit that contains a known material cataloged by a geologist with the USGS.

Good in Bad

You know how they say things happen for a reason. Well this recent firing made me read up on a lot of stuff I'd already learned but had maybe not remembered lately. It also made me do a bit more digging to find some things I did not know.

For some time now I've been interested in doing crystalline glazing in my studio. In fact it was Wally Schwab who first introduced me to crystalline glazes when I studied under him at PCC Rock Creek. I'd also done quite a lot of research into microcrystalline glazes at MHCC with Don Sprague. Since then some advances have been made by other potters to fire these glazes at cone 6. When I looked at these before I'd found a cone 1 crystalline glaze as well, but had lost the recipe. Well I found it yesterday, so I'll be tinkering with that one soon thanks to Charlie Cummings post on Clay Art Thread. I also did some research into the firing schedules and found out that the crystallization is happening upon cooling, but a very slow cooling where the kiln is held at the 1830 - 1900 degree mark for four hours. What's interesting is this is when the iron in cone 5 iron reds is held to facilitate crystallization as well.

As you may know there is a huge difference between Orton cones. The large ones drop much faster than the small ones, in fact a large cone 6 drops at 2228 where a small doesn't drop until 2291. Sixty three degrees doesn't seem like a lot when you're talking about thousands of degrees, but it's enough that it could make a glaze go from stable to runny. It's not just the temperature but also the time it takes to get to the higher temperature.

Charlie Cummings
Macrocrystalline Cone 1
Frit 3110 - 43
Zinc Oxide - 23
Silica - 16
Lithium - 9
Laguna Borate - 9

Firing Up, Firing Down

After doing a lot of reading over the last several days. I think I've found the answer to the glaze firing problem I had recently. The potters who fire reds fire up and then ramp back down slowly. Some shut the kiln down and then manually hold the setter back on for 20 minutes in the 1800 - 1900 range to allow the crystallization of the iron molecules that reflect the color red. This is where Crystalline glazes also ramp down to and hold for a number of hours. Some potters however who were doing reds actually fired back down slowly to achieve the red coloration. This is also used to more slowly cool a kiln to allow a glaze to stop bubbling and heal over. In my case the cone malfunctioned and I did not have witness cones inside (big mistake) to tell me when I'd reached peak temperature. I've decided to do my glaze firings based on witness cones instead of relying on the setter to shut it down. This way I can fire back down slowly cooling the glaze.

Misfire

After some consideration I'm fairly certain that my trouble with this firing was a cone malfunction combined with a quick cooling. I did a leak test on some cone 10 pots I put in the firing and they are vitrified. Some parts were unglazed and did not leak. The cone 6 glazes I used were supposed to be matte and completely melted and ran down the pots. The kiln took a very long time to reach top temperature, like 4 - 6 hours longer than I expected. I'm fairly certain that the kiln actually hit cone 8 - 10 range. I'm going to purchase a packet of cone 5 and a new box of cone 6 and try these glazes again.

Lack of success

Well my first cone 6 firing in my new location was a failure. The kiln cooled too quickly trapping bubbles in the glaze on all the pots. The matte transparent also came out a shiny and clear which leads me to believe that the long time the kiln took to reach temperature made the glaze over mature. It became fluid and started to run down the pot as if it were not a matte glaze at all. Quite disappointed in this one, however I did get some great color response in both the purple and the blue. As Churchill said "You can always count on American's to do the right thing, after they've tried everything else." Looks like I need to wrap my kiln is fiber or something.

Cone 6

Wow my small electric kiln takes a long time to reach cone 6. I'd been doing cone 1 for a while now which is about the top end of lowfire. Cone 1 makes vitreous durable pots out of low fire white clay. However the clay has a sticky feel and is not as nice to throw as cone 6 porcelain or stoneware. Besides I've got some great cone 6 recipes to go with some really great cone 6 clays that I enjoy working with. I'll continue to do cone 1 because it's fun and cheap.

I have a bunch of cone 6 porcelain that I really didn't like so I wedged in some mulcoa 47 grog 35 mesh, which stopped all the finicky problems that high spar content clays have. With about 10% added grog to the wet weight, the porcelain takes on a whole new personality. It retains it's plasticity, and gains structural integrity, and fast drying capabilities. This clay went from S cracking while drying unless you kept it under plastic for days and flipped it on the rim while it was still quite wet, to being able to throw plates and leave them until the rim and inside is leather hard, flipping and trimming the majority of the foot while wet, then coming back and finishing off the last bit once it's leather hard. Never being covered in plastic and drying in the kiln room at about 85 degrees of dry hot air in the room. I love porcelain, but the forgiving nature of a clay with grog is just so much more satisfying. With a full schedule of classes I need a forgiving clay that will wait if I want it to, but can dry quickly if I want it to as well.

I've also been making some "Patrick Horsley pots" which is really my take on his techniques. I've really been enjoying the method which has opened a whole new design element to my work that was not possible before I took his workshop. I've taken to making these figurative jars that are flattened to an oval and have a wider shoulders and body with narrower bottom half and narrow neck. I find them fun to make as well as aesthetically pleasing. The porcelain with grog has been an effective clay in making these pots.

Research

I'm a big fan of ceramics books. The one drawback of my book library is that a lot of it is dated material in classic ceramic books. One such thing I found was Jack Troy's book Salt Glazed Ceramics. The book covers how to make salt glazed ware, and salt kilns. In his book he used Portland Cement because the newer alumina refractory cements weren't available when he wrote the book. Toward the end he discusses the ongoing research in castables which he discusses adding alumina to the cement in ratios. Well I did a lot of reading and found many articles talking about castables and several covered this in detail claiming that adding alumina oxide or alumina hydrate to a cement would not work.

I did a lot of reading on castables and refractories. I read research papers books, blogs, discussion boards, websites, technical data sheets etc. All of this research led me to a basic formula for a medium to light castable cement which was mentioned in my last blog consisting of, 2 parts fire clay, 2 parts grog, 2 parts saw dust, 1 part cement. For this recipe I chose to use Ciment Fondu because of the fairly reasonable price of $44.00/bag-94lbs.

We used this product in my mom's backyard oven. I have some concerns about the oven because the castable will shrink considerably and my parents decor design has a flaw. They wanted to use bricks on the outside and we'd already decided to use a castable cement. Well the cement is going to shrink some when I fire the oven off the first time, and the bricks will not shrink. This means that the interior will shrink away from the bricks and there will be a gap. This would not be a problem except we used a sprung arch design in the top of the oven for maximization of space. As it shrinks it can become unsupported and crack, or even fail. I'm going to strap the thing together with steel support braces prior to firing, but who knows if it will work or not... The one thing I could not find (and did not test because of time constraints) is the shrinkage of this castable upon firing. I guess I should hurry up and fire off the blocks I've made.

Long time no blog

It's been a while since I've blogged because I've been fishing a lot and not making pots so much. I do however have the studio in place pretty much. At least enough that I can wedge clay and make pots. So I'm doing that and awaiting the cash flow to complete the kiln project. I'm only short a few hundred bucks, but it's amazing how much a few hundred bucks is when you don't have it to spare.

The great thing is I've been able to get my feet wet with castable cement in the building of a backyard cook center for my mom. We've built a catenary arch kiln style oven with a small arched firebox in the bottom and a level cook top in the oven chamber. I'm pretty excited to finish the piece off this weekend. I'm going over there to build the final frames for the big catenary arch which is going to be the top, sides and back of the oven. 

To build this thing we've used lincoln 60 fireclay, pine shavings, fine and course mulcoa grog, and Ciment Fondu which is a 40% alumina refractory cement. This was used in a 2,2,2,1 parts formula. 

2 Fireclay

2 Pine Shavings

2 Grog

1 Ciment Fondu

We had to substitute some sand to complete the cook top because we were running out of aggregates at the time. We also had to substitute some Portland Type II cement into the cook top because we ran out of Ciment Fondu. So the top of the firebox itself has about 2 inches of good refractory cement, and the top of the firebox layer or cooktop has about 2 inches of Portland Cement. For this application it should be just fine, although I did have the idea that I would burn this thing to red/orange one time to cure it and I don't see that happening with Portland Cement. We'll see how it goes, but I certainly don't want to push the cook top the the point that it fails.

The tall arch we're about to build is going to be a 2" layer of medium density castable just like the firebox pieces were, followed by a 3 inch layer of light castable made with perlite. In the big arch we're going to put holes which will later hold spring mounted bolts for a flange which will hold the doors. There will be two doors on the oven one small one down below for the firebox and one up top for the oven which will be quite large.

Keep it Moving

It's been a period of constant transition for the last year. I've been unable to set up shop for very long because we keep having to up and move. I'd planned this time to stay here for at least a year, but here we are again in a position where we need to move. The current living arrangement has failed to work as intended and I have to give up my two car garage, my huge office and my new garden space that's full of vegetable plants. I'm really bummed out!

So we're looking at places somewhere outside Vancouver. A couple look promising, but no concrete plans as of yet. One little place on an acre in Orchards is particularly interesting, but it has no garage or basement. I could build a cheap out building made of Plastic and cattle panel for a greenhouse and a shop.

The good news is, I have done the research and can now build a large castable kiln for a few hundred bucks. I'll be building the arch frames and ramming my mom's oven by the end of the month.

The bad news is the move is going to cost me all my student loan money and I'll likely lose all my vegetable crops when I go.

Redware

So here I am with 300 lbs of porcelain, and I'm itching to make replica Pennsylvania Redware. The bright red clay with white slip trails covered in a bright amber glaze have me mesmerized into buying a couple boxes of red clay in Tacoma this weekend when I'm up there. The question is will I have the money for the 10 other things I'll end up buying when I go?

http://www.ceramicartdaily.net/booksales/Electric_Wilz-3.pdf

Oven

So I've been testing some castable recipes for my mom's Earthen Oven we've been prepping to build in her back yard. I dug through some old posts on the old clayartcenter.net forum and found several referring to a 4,4,4,1 recipe. My tests are as follows.

#1
4 Fireclay
4 Grog
4 Charcoal (Crushed)
1 White Cement

#2

4 Fireclay

4 Grog

4 Charcoal (Crushed)

1 White Cement

1 Talc

#3

4 Fireclay

4 Grog

4 Charcoal (Crushed)

1 White Cement

4 Pearlite

The original recipe called for grog ranging from dust to 4mm particles and sawdust ranging from dust to 3/8". I can get grog that size, but I had a difficult time finding combustible materials that size range. I can get dust and I can get chips, that's pretty much it. So I figured if I crushed up some of this Mesquite Natural Log style charcoal, I'd get the size range. It worked but I gotta tell ya, crushing much of anything by hand with a 8lb hammer isn't the most fun I've had. 

The Talconic Castable is really close to the original, but I was aiming to have a slightly better heat dispersion. I was also thinking it would cure at a slightly lower temperature. We'll see how it performs through the test I made. It's just a slop brick form, but it's got an arch built into the bottom so I can measure any sagging or warping that might occur. I believe this is only about 7.2% talc by weight, so it shouldn't cause too much of a problem.

My concern is the white cement I purchased. The spec sheets for the material claims it boils at about 1000C. Does this mean the castable will begin to mature near Cone 06? While I realize her oven won't get to that temperature after the initial firing to cure, I'm wondering how these guys are using white cement in Cone 10 castable kilns? Or are they using a different Cement? All the research I've done says they use white cement for earthen ovens. One post I found the guy claimed to have used a recipe from Jack Troy's book published in 1977 called Salt Glazed Ceramics. In that kiln he claims to have used white cement, and fired with salt for 10 years before the arch failed. That doesn't say how many firings. He could have only done 10 firings for all I know. I just purchased the book from Powells Books to take a look. When I do build a castable kiln, or castable slab floor (which I'm doing in the kiln I'm building now) I expect it to hold up for 100 firings or more.

Stay tuned for the results.

Mid-range Porcelain

A while back I decided to buy a box of pretty much every kind of Cone 5 - 7 Porcelain I could get my hands on. There were a few I couldn't get at the time, but I have like 8 different kinds that were in stock. I finally was able to drag my wheel out and get to work.

The first box I grabbed was OH - 6 made up in Tacoma at Clay Art Center. It's got good throwing capabilities, as I thew a 10" cylinder with ease right off the bat. It promptly broke down when I expanded the cylinder. I can't fault the clay too much it is porcelain after all and I was abusing it like a stoneware with grog, trying to push it to failure. 

I did make another pot, and it cracked upon drying. I got a ring crack on the bottom of the pot, which tells me that it dried too long on the bat prior to trimming. I probably need to slow the drying a bit as well, or be more attentive. I could trim quite a bit wetter. I waited until the pot was easy to trim. It had been sitting on the bat it was thrown on for about an entire day. I could probably have flipped it after 6 or 8 hours and then trimmed it between 8 and 12 hours. My garage is drafty but cool because of the big cement slab being directly on the ground. There is also an apartment built above the garage that provides protection from the sun, so it stays cool if it stays shut.

I'll have to give it a few more tests, but I still have many clays to go, so if this one proves to be too picky I've got some 35 mesh Mulcoa with it's name on it. It'll behave, one way or the other.

Bio-diesel

I did some research into fuels recently because of all the recent backlash against bio-diesel. What I found was striking to say the least.

Seed Stock/Oil Yield in pounds per acre

Peanut/764

Canola/600

Rapeseed/600

Safflower/600

Soy/600

Linseed/350

Corn /200

Cottonseed/200

This data was derived from 

Buchanan, G. (2010). Increasing Feedstock Production for Biofuels: Economic Drivers. BRDI , 3.

From the data above it's plain to see the largest yielding conventional crop currently grown in US soils would be peanut.

The basic idea of growing crops for fuel instead of food could be considered a bad thing in and of itself, it's definitely a bad thing to grow a conventional food crop which produces a very low quantity of oil as an oil crop. Yet this is exactly what the US farmers are doing. Corn is the lowest yielding crop that could be planted for fuel.

Under the current methods of production I cannot endorse bio-diesel. I thought I'd be the last one to encourage government involvement in private industry, but the bio-diesel market needs to be regulated. Corn needs to be taken out of the Feedstock for bio-diesel production. 

However there is nothing wrong with using waste oil of any kind as fuel be it corn, peanut, soy, animal oils even. Most of these are low in emissions and have a high energy output. I'm personally inclined to purchase land and become a peanut farmer for the production of bio-diesel myself. The yield being nearly 4 times that of the corn farmer, the comparative advantage is astronomical.

Cerameconomics

In pricing out materials I've found an array of prices for the exact same materials. I'm told it's because some places purchase large quantities of materials at once and have old stock on hand which they can sell me for cheaper. Well I'm here to tell you that the guy down at Georgies who told me that can stick his stock on hand where the sun don't shine. Their prices are outrageous and I see no other reason but that they are price gouging because they are pretty much the only game in town for ceramic artists.

Up in Tacoma however I have been pleasantly surprised by not only the products offered to me by the Clay Art Center, but also their prices. Their customer service is great on weekdays when the boss is there. On weekends the head honcho is out and the place is packed with way to many customers to be effectively helped by the staff on deck. That aside it's a pleasure doing business with Clay Art Center in Tacoma. They provide me with my wet clay, dry clay, raw materials for glazes, and the best part is they're willing to put my order on the back of the next truck headed for Stark Street Studios in Portland for a reasonable fee.

Nitride Bonded SiC

When considering the many options to build my kiln I first began to price materials. Oh boy there are a lot of materials to choose from these days. When I first started I didn't know my burner port from a whole in the ground. After some deliberation I found the cost wise Ceramic Fiber was going to be the key to my success in mobile kiln building.

I had decided to use a brick floor for durability and stability. When trying to price out bricks, I'd first looked at IFB's which I'm sure would be nice, but quite costly. I then found several deals on websites such as alibaba.com where some international company based in China posts refractories and some base price. After attempting to deal with them I quickly found that it was more trouble than it was worth. I would be quoted different prices than were posted, they didn't actually have the material on hand and were giving me "custom order" pricing. Once I realized I needed to buy local I tried to find the most local guys I could get my hands on. I had stumbled across many blogs and threads talking about many refractory companies, such as AP Green, Narco, Harbison Walker. I searched and found ANH's website online and quickly found my local supply warehouse located out on Jennifer RD in Clackamas OR. They're a good bunch of guys who sell some superior products such as the Ceramic Blanket I purchased which was made in the USA. 

I ran out of dough before purchasing bricks from Harbison Walker and had been perusing the internet looking for deals. I stumbled on another company which is extremely local Thermal Ceramics,  which has a manufacturing facility located out in the Rivergate District in N. Portland. Thermal Ceramics is the company which produces the Kaowool product that ceramic artists know so well. I purchased another product from Thermal Ceramics called Cerachem which is a 2600 degree rated blanket that I'm using as the blast face on top of the ANH blanket which is rated at 2300 degrees. After talking with Jeff for a while he and I both came to the conclusion that in my next kiln which will be a salt kiln, I should test some SiC bricks in a small test kiln. Well after giving the idea quite a bit of thought I figured I'd try them in the floor of my new oil kiln as well to see how the hold up. I decided this because they will be subjected to some of the most extreme flame conditions I can imagine. And if they don't work I'm only out a couple hundred bucks, and can just rebuild my floor with IFB's or high duty bricks with ease since the kiln is made of blanket anyway. A few hundred bucks later and I had enough bricks to build a basic kiln floor with bag walls and all. 

I really can't stress enough the impact these refractory guys have had on my project. When I started I was full of questions, and now I have still have questions, but I have some answers as well. I recommend both ANH and Thermal Ceramics for your refractory needs.