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Black Raven

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So I just realized standards 112 has granular manganese in it. I am really thinking I am over worrying about this black raven clay having less than 1% when I have always been working with manganese already anyways.

 

I think if I just keep my studio cleaner and make sure my vent is always working properly I shouldn't have any major problems. I already dont pot when I am firing my kiln anyways. I just use the time as a break and focus on school work.

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 I have used that Standard 112 for years.  If I do any sanding, I always wear a dust mask.  My kiln is in my garage, unvented.  Never thought about the fumes.  Now that I know this information, I will be more careful when using this clay. 

Here's an article I found on the subject:

 

Manganese in Clay Bodies

Manganese materials (powder and granular) can be ground from a variety of ore materials, thus the powder is not a pure manganese oxide. While they are often considered a nuisance dust the ores often also contain significant amounts many other compounds like barium, lead, quartz.

Among potters and hobbyists, the most significant use of manganese is in metallic raku fired glazes (20% or more). However high amounts of manganese dioxide can also be used in bodies for dark grey and black colors (up to 10%). These can likewise produce metal oxide fumes that can be very harmful. Unventilated indoor kilns pose a significant threat but standing downwind or close to outdoor kilns can also be a serious hazard.

Before classifying bodies containing manganese granular (to create a speckled fired surface) as dangerous the situation must be put into perspective. Such bodies contain only about 0.2% of 60-80 mesh manganese granular. The vast majority of particles are encapsulated within the clay matrix. Most of the tiny percentage of particles exposed at the surface are engulfed by the glaze. All of the tiny number of particles that actually bleed up through the glaze to either near or at the surface have been significantly diluted and stabilized by the glaze melt that surrounds them. Thus the total area of leachable manganese glass on a functional surface is extremely small.

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Yea. I have read that before, thanks for the information anyways though. I have been reading constantly about all this stuff. The clay body states that it has less than 1% manganese dioxide. Like the specs, it makes me not worry as much. 

 

I have my kiln in my garage as well, except I run a vent kit out the door and close the door down all way except like 3 inches, leaving the vent pipe going about a foot out past the door. I used to fire my kiln without a vent a long time ago, and the smells in the garage were awful, I fired this way 3 times then built my own kit. Now with the kit I don't smell anything ever. So I know my vent is working pretty well. I also constantly check the seals and areas where it could leak and make sure everything is sealed well. 

 

I think my major concern is the clay dust, and I should have safer practices of that anyways, so I am just going to start mopping my studio anytime I get clay on the floor. I used to get clay on the floor all the time, but nowadays I rarely make a mess. So I think all together the black clay will make me more safe, as funny as it sounds it will make me less lazy. Terrible I know.

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I would love to see your work if you use the black clay. I bet it would be fabulous looking.  Years ago I bought a clay and fired it to 10. It turned out black, can't for the life of me remember what clay it was.  I made a spare bedroom a pottery room.  It can get dirty, but I don't use a wheel.  I do everything hand built.  Never could master the wheel. After reading all of this, I will be cleaning better when I'm done.

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I have some test tiles of it and have made slip with it.. the slip can be fired to ^10 ... i have fired the slip to ^6 with no issues... got other projects on the burner rite now..

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Cool man, Im excited for you.. I have about 15lbs of Earthenred left to throw and im diving in the Black Raven... ill probably do some glaze test with it either this weekend or next... just depends on how dry my pots are... we need to work together and see what we can come up with, this Black Raven is a interesting clay body... i have Grellog porcelain slip and Earthenred slip already made... Cindy loves glazes,we have alot of different kinds/colors, i need to start making my own very soon, save some change..

 

What color glaze are you making?

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So I have been working on this black raven stuff for a while. I finally got some glazes to come out nice on the test tiles.  I took these with my crappy camera phone so you can't see how glossy it really is, and the pictures are kinda blurry, but I am making progress on getting a nice glaze for the mugs I am looking to make with this clay body showing.

 

http://s1183.photobucket.com/user/josephrosenblatt/slideshow/Black%20Raven%20Test

 

However I can't for the life of me get rid of the bloating. I have tried firing to cone 4 5 and 6 and I still get bloating. So at this point, I know it isn't over firing that is the problem. All of these firings have been verified with self supporting cones on 3 levels(bottom, middle, top) in my kiln.

 

I have been doing a slow bisque that takes around 14 hours. The pre-programmed one on my L&L.

 

However I am going to move into creating my own bisque schedule for this clay. I am thinking about something like holding the kiln at 1500 for a good 15 minutes, and adjusting my vent to take in more oxygen into the kiln during my bisque firings and lower it back down for glaze firings. This way when I burn out more carbons I will have more oxygen to keep it oxygen rich environment. I thought the slow bisque would be enough, but it isn't.

 

So that is my first update. I finally made a breakthrough in getting glazes to actually come out on the clay without a white slip over it.  I am very happy about that.

 

Pottery is not for the weak, if you want to make great things you really have to put in the time to test test test and test, and then test some more. Literally I am at the point in pottery where I do more testing and hammering than keeping pots. The most odd part about it, is I find so much joy in my tests. Like I opened the kiln and I see color and I am like WOOOOO. I jump around my garage dancing. My wife looks at me like I am crazy. She is starting to understand that I want to become a master! not just simply a potter.

 

Meanwhile here are some mugs that will be getting the hammer because they are going to bloat after I fire them!

 

http://s1183.photobucket.com/user/josephrosenblatt/slideshow/Black%20Raven%20Mug%20Practice%20Test%20mugs

 

Either way getting in the practice.

 

When I figure out my bisque schedule that I dont get bloating I will post it for others who want to try this clay.

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Another approach would be to make your wares of white stoneware and, while still leatherhard, apply a thin slip covering of the Raven clay body -- maybe just the exterior of the cup or just the lower portion you want to leave unglazed.

 

Your pictures show a really metallic sheen to the unfired Raven; much more than I've gotten using Standard 266.

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bciskepottery - I already tried the Raven slip over  Little Loafers.. It bloated as well, it wasn't as bad... you could definitely tell though... he has some pretty big bubbles in those pictures, mine were smaller but more of them... It need some Bean-O , a double dose actually ...

 

~Jim

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Here is the look I am going for. I have decided to start coating my black raven in a white slip right after the leather hard stage. So I trim, attach handles then dip in slip. 

 

This is the type of mug I am wanting to make. These were just test mugs so I wasn't super careful with the glaze and slip, I just trying to get stuff into the kiln so I can repeat my testing as fast as I can. However you can see the colors that I am going for. Something very gender neutral, but also that could go well in any kitchen.

 

The other 3 mugs were a brown speckle clay.  As you can see. Plenty of bloating going on. I really wish I could fix it. If anyone has any ideas please post them. I am running out of options. 

 

http://s1183.photobucket.com/user/josephrosenblatt/slideshow/Test%20Firing%20Black%20Raven

 

I read somewhere that you can reduce bloating by reducing the amount of oxygen in the kiln during the final phases of a glaze firing. I am not sure how accurate that is, or what it would do to my glazes. But I was thinking about trying it this week, anyone ever heard of that?

 

One thing I am thinking is that I might not be getting enough oxygen during my bisque firing. I have a Easy 18 L&L and I didn't drill any holes for my vent. I think that I might need a more oxygen rich environment for this clay, so I am debating on following L&L's instructions for drilling a holes around my lid. Not sure if this is the right decision or not, but testing and time will tell.

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I have used the Black Raven, but only in slab work, I made some soap dishes for my mother in-law but I left them raw, no glaze just a fun texture for decoration. I had no issues with bloating either. If I remember correctly I did make a few test tiles with some glazes that I like, but as I recall the glazes reacted poorly to the clay body, and at the very least speckled, I think clear that I like to use did worse than that. Needless to say I am sure there are glazes that would work well with the Raven but just not any of mine.

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I have tried Raven as well. Glad to see another hometown potter on here! I'm up in Gainesville right off the lake (lots of red clay here ;) ) Are you using an Olympic Kiln with Bartlet controller?  I got bloating and blisters as well no matter how slowly I fired, I even tried the ramp down method for an extra slow cooling. I found that my kiln is overfiring a bit. I am now going to start to bisque fire all my wares to cone 05 and then glaze fire to cone 5 with witness cones. So I may give it another go as a complete clay body after a while if that method works out. I turned it a lot of it into a slip for the time being. Here are some of my test results using a few of Stone Mountain Clay's pre-made glazes on the Raven clay body.

 

 

 

Leapard Agate

and

Azurite

image11.jpg?w=640

Key Lime

and

Caramel Corn

image21.jpg

 

Ruby Slippers

and

Ginger Mist

image31.jpg            

 

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Thanks for the pictures. Those glazes are nice. 

 

I am firing a small 2.6CUFT L&L with the dynocontroller. I have tried a lot of stuff and I am getting closer I think to solving the issue. I am starting my glaze firing right now so I will see if I don't get any bloats this firing with a super high oxidation bisque firing.

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Grype,

 

As I recall bisque was cone 06 ande glaze was 6 on my test tiles, but on my ray slab work I did not bisque but slow fired to cone 6. They were soap dishes that had been bone dry for weeks, and they were in a community kiln with work that was being glaze fired.

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Well, I finally did it. After about 5 months of testing small doses of black clay in my attempt to find a correct bisque for my wants and needs I have found a schedule that completely removes the bloating from my black clay. I should also add that I increased the oxygen in my kiln by increasing my vent intake to about 60% closed, and I drilled a 2nd hole in my kiln lid. My little kiln just needed more air. Also my glazes look much better now that I added the 2nd hole. Damn kiln was built so well it wasn't getting any oxygen.
 
As promised if I found a bisque schedule that would solve the bloating issues I would post it. So here it is:
 
Step  Deg/Hr  Temp  HoldTime(hrs:min)

1       80          180     2:00 - (if your clay is 100% bone dry you can skip this hold, or reduce to your needs)

2       150        600     0:00

3       240        1250   0:00

4       100        1500   1:00

5       150        1650   0:00

6       200        1850   0:00

7       108        1975   0:10

 

This bisque schedule focuses on a very slow burnout of the organic and inorganic carbons, so good for those dark bodies that I like. It is a slow bisque and takes about 18 hours to complete.  It also with the hold ends up about cone 03. This makes my glazing step slightly more difficult but since I mix my glazes into a gel consistency using a tip from digital fire based on establishing the specific gravity, then gelling the glaze, then establishing thixotropy. So even if my pots don't absorb the glaze right away, they gel onto the pot then dry slowly. So far having beautiful results and I love how I don't have to deal with drips.

 

If interested in thixotropy, check out this: 

 

 

 

So I am pretty happy, now I can work some more with my black clay and white slips. Pretty excited about that. I also have some good news in other areas as well, that my testing of removing gerstely borate in my glazes is paying off. Much smoother results, less amber tinted, and a better gloss finish. All around good news for the last 5 months of testing I have been going through. 

 

Today has been a wonderful day. I now can move into testing for durability, and then MAKE SOME REAL POTS, if I remember how!

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HOORAY FOR YOU!   GLAD THAT IS OVER!  i think lots of us are happy to see that you worked it all out.

 

now, i could not get past the statement that you put the white slip right AFTER the leather hard stage.   why the h do you wait so long?  apply it while the clay is still dampish and it will all dry together.  slip is only clay unless you have some zany recipe for making what is essentially wet clay out of dozens of ingredients.  not yelling at you, just wondering why you wait so long.  get it over with so you can do something else.

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I like to trim my pots, add handles etc, then apply the slip. I usually just dip the pot right in the slip and pull it out no problemo. Worked fine so far. Then I can handle the pot and run my fingers over the slip to expose the black clay below. I rather like the method. 

 

I never think your yelling at me. I dunno why I do the things I do. I just do!

 

As far as the slip. I just chop up little pieces of clay, put it in a bucket, cover with water, wait a few days, mix it up, sieve it, mix it again and its done. Comes out all nice and slippery. 

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