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JBaymore

Member Since 06 Apr 2010
Offline Last Active Yesterday, 11:02 PM
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#91685 Proper Reduction Firing Schedule

Posted by JBaymore on 29 August 2015 - 05:36 PM

There are many variables involved in developing specific cycles for specific effects with specific bodies and glazes..... but in general, the concept of "body reduction" as somehow being totally separate from "glaze reduction" is not quite accurate to what is actually happening. 

 

It is all a "blur" that runs together seamlessly. 

 

If you want to cause reduction effects on compounds in the body, you need to start reduction before the surface of the clay body or the surface of the overlying glaze layer becomes gas impermeable to the two prime reducing agents in firings; carbon monoxide and hydrogen.  Carbon monoxide is the main reducing agent in most of our firings because hydrogen at elevated temperatures is so reactive it usually "finds" available oxygen first in the kiln's gases. 

 

Note that carbon particles are SO large that they are quite non-useful for "reduction" in a kiln.  They don't easily get into the clay or glaze surface.  SO all that smoke some people get on gas kilns..... wasted effort. (Unless you are doing carbon trap shinos! ;) )

 

So the molecular size of the reducing agent getting into the clay is the first question in developing the firing cycle. As the body tightens, it does not allow the gases to get to the compounds below the immediate surface.  The main compound that we use to get "reduction" colorations in our work are iron compounds, reducing the valiancy to the black state from the oxidized red state.

 

FeO is a powerful flux on silica (SiO2) and which also happens to color the resultant glass at the same time.  So as the reduced iron 'bleeds' into the glassy phase of the body it also colors it (grey). This is particularly effective on small hematite nodules....giving lots of reduced iron in a small physical location (iron spotting). 

 

When the SURFACE of the tight body that is NOT under the glaze is then allowed to get in contact again with oxygen as the kiln is shut off and cooling, the surface turns to the reddish-browns we associate with "reduction" firing.  The body, if it is vitrified, is gas impermeable to oxygen ... and the inside it remains a greyish coloration. 

 

Importantly, the diffuse reduced iron compounds in the glassy phase of the body start to also work their way into the melting glaze layer over the already reduced body.  If the glaze surface starts to melt and become gas impermeable to the reducing agents before reduction had occurred, the body under the glaze does not get reduced.  So the interaction of the body with the glaze is less.  Plus the coloration of the body will be base on the red state (or the original state) of the iron compounds. 

 

Once the glaze surface is totally gas impermeable to the reducing agents then no amount of reduction will reduce stuff own inside the glaze layers or the underlying body (except maybe because of the bubbling of the glaze allowing some interior matter to be reduced on the surface). And once reduced inside, when the kiln is shut off and cooling and exposed to oxygen, the glaze surface also, just like the clay surface is oxidized.  Unless you fire down in reduction, or pump the kiln full of an inert gas (industry does this kind of stuff) the whole outside of "reduced" pieces is re-oxidized. 

 

Different glazes and different clay bodies have different firing characteristics.  There is no "one size fits all" firing cycle.  You have to find what gets the best out of your clay and glazes.  And different glazes and bodies often are not getting optimum effects when fired together in the same cycle.  What is great for one may be just OK for others.  We are back to that stock phrase of mine.... "test, test, test".

 

At one point I did some research on one particular celadon glaze on one particular body.  Over a LOT of firings it was determined that reduction at a certain intensity had to occur before cone 04 and after the kiln reached cone 4 it made absolutely no difference how the kiln was fired as to oxidation or reduction levels.  Reduction too low below 04 (cone 012 and down), and the body exhibited a tendency to carbon core and bloat and bleb.  Optimum turned out to be slightly oxidizing or neutral fire up to about cone 06 to 04 to start a light reduction, and that level was maintained at the same level until cone 4.  Then fired in slight oxidation to neutral to the cone 10 end point, then cooled in oxidation.

 

Some thoughts for ya' there.

 

best,

 

.......................john




#91668 Pc Members Juried Show

Posted by JBaymore on 29 August 2015 - 01:37 PM

Maybe now that I am not busy being on the Potters Council Board.... I'll remember to send in an entry for the first time in a number of years. :)

 

Thanks for the reminder Marcia.

 

best,

 

....................john




#90608 Going Price Of Mugs

Posted by JBaymore on 10 August 2015 - 05:33 PM

 No worthwhile retail outlet is going to keep a line where the maker is selling to the public at the "wholesale" price.

 

A mistake too many people make.

 

The sort of "standard" way to look at this is that when you are MAKING pots.... you are a potter.

 

When you are SELLING pots... you are a retailer.

 

The Retailer BUYS the pots from the Potter at wholesale.  The potter should be happy with the price that he/she got paid for the work and well cover the costs, labor, overhead, and a profit factor. 

 

Then the Retailer adds the appropriate markup to the wholesale price they paid for the work they are now selling to cover the costs, labor, overhead, and profit involved in RETAILING them (and craft fairs and such ARE closely akin to retailing and DO have similar expenses to cover).

 

best,

 

.................john




#90595 Going Price Of Mugs

Posted by JBaymore on 10 August 2015 - 02:20 PM

There is a lot to be thought about as one looks at potential target market and also what is known as price positioning.  And about assessing the available market or the target market.

 

It you do not have the ability to even reach higher end buyers... then making $1000 cups is going to an exercise in utter futility no matter HOW wonderful they are.  Conversely... higher end buyers likely will not be seriously looking at BUYING $10 mugs.  Simply because the artist does not think enough of their own work to price it appropriately.  So they will assume it is 'junk' from their point of view.

 

And if they even bothered to stop and look at them... and found them being something they would consider owning...... they likely would tell you right up front that you are absurdly underpricing........ and encourage you to raise the prices (thereby also raising the value of the $10 investment they just made ;) .) 

 

Matching the work to the venue and the market is key.  And pricing consistency.

 

best,

 

........................john




#90467 How Often Do You Gear Up For A New Direction Or Experimentation In Your Work?

Posted by JBaymore on 08 August 2015 - 02:24 PM

For me it is "Darwinian".  Evolution... not revolution.  I don't "gear up"..... I just get my hands into the clay and listen.  Change happens over years.... not weeks or months.  Materials slowly change if or as the need of the pieces dictates. 

 

best,

 

..................john




#90142 Going Price Of Mugs

Posted by JBaymore on 03 August 2015 - 11:09 AM

  If you want to make $20 per hour then you need over $30.00 per piece.  

 

The kicker problem here is that a skilled craftsman in other fields like a car mechanic, builder, and so on are looking at hourly rates in the $50.00 plus range (plumbers get more than brain surgeons ;) ).  Burger flippers get $10 an hour... and the move is on to make minimum wage $15.00 an hour.  Some places it is.

 

$20 an hour is NOT a good wage these days.

 

So if you are a long term and skilled craftsperson, you SHOULD be looking for at least $50 an hour.  Or well more if you are later career.

 

It is WAY easy to underprice for your skill set.  And when you price correctly...... your market narrows fast.

 

best,

 

........................john




#90141 Going Price Of Mugs

Posted by JBaymore on 03 August 2015 - 11:04 AM

The "building the business" phase is no different than that experienced by just about ANY business.  The prime reason for the failure of new businesses?  Under capitalization.  You need to have a business plan that LOSES money for the first X years. 

 

Those "losing shows" one deals with in the early days of the business are part of that capitalization issue.  Eventually because you have done those losing shows.... you have honed the business to get into the winning shows.  Then the business goes from red ink to black ink.

 

Some call it "paying your dues".

 

best,

 

...................john




#90139 How Much Do You Stay Within Glaze Limits?

Posted by JBaymore on 03 August 2015 - 10:55 AM

Well said there, patat.  Of course, I'd expect that from someone with the chem background like yours. 

 

The negative proof is the key, isn't it.  No simple answers.  The deeper you dig, the more nooks and crannies in the cave you find to delve into.

 

I use some lead glazed pieces for food also........ Japanese Aka Raku Chawan for tea ceremony.  I have inspected the gun ;)  and know it well. 

 

For many, many years I have been trying to get accurate information on the toxicological issues in ceramics out to people.  In the MIDDLE GROUND...... not the typical "we're poisoning everyone" hysteria....... and not the "I smoked 100 packs a day and drank 20 gallons of whiskey a day and I'm 83 years old" denial.

 

It's that old 100% correct ceramic answer adage....... "It depends.  It depends."

 

best,

 

..................john




#90028 How Much Do You Stay Within Glaze Limits?

Posted by JBaymore on 02 August 2015 - 09:40 AM

Been doing a lot of reading today and found this. Fits in well with the topic of limit formula and where they arrived from. Interesting thoughts about B2O3 and if it's flux, stabiliser or glass former.

 

http://www.frogpondp...literature.html

 

High Bridge Pottery,

 

Ahhh.... you now have officially headed "down the rabbit hole".  ;)

 

There is no end in sight.  "Resistance is futile".

 

best,

 

.......................john




#89961 Do You Store Your Glazes Dry Or Wet?

Posted by JBaymore on 01 August 2015 - 08:54 AM

 

Wet....30 gallon garbage cans.

best,

..................john

How many glazes do you use? 5 glazes=150 gallon of material, 10 glazes=300 gallons.


WOW. you continue to inspire us slow polks.

Jed

 

 

In the large volume sizes.... 9.  Couple of small 5 gallon types also for some limited use stuff.  The 30 gal cans are  not dead full.... maybe kept at between 22 and 26 gallons in each.

 

I find nothing worse to freedom and spontaneity than trying to glaze with limited material or space.  I want to be able to pour, dip, trail and so on without "worrying".

 

best,

 

.................john




#89682 Qotw: What Makes Something Qualify As Hand Made?

Posted by JBaymore on 28 July 2015 - 09:17 AM

Oh man........ "can o' worms".  Can't wait to see how this develops.

 

best,

 

..................john




#89558 Yunomi

Posted by JBaymore on 25 July 2015 - 12:49 PM

Grype,

 

There is another "point" hiding in here in the thread that is "sub-text".  Market segmentation.

 

People who make certain styles of ceramic work sell that work to people who LIKE that style of work.  So there is some inherent 'sorting' of the people who might use that rough bottomed yunomi (or vase, or plate, or ?????), and the purchaser made a decision when purchasing that the rough bottom on the piece was not an issue for THEM.  They are aware of it and they will "deal" with the implications.

 

People who feel it is an issue.... just won't buy it.

 

One of the inherent problems to selling online; the buyer cannot handle the work before purchase.  Can backfire on both the purchaser and the potter in this kind of aspect.

 

Some potters (myself included) tend to make a particular type of ware that they love to make, and then find the market that shares that same aesthetic bent.  It is a more difficult path to establish than looking at what the masses want and then making that, but it is rewarding.  There are people out there that will not care about the roughness of the foot on the piece (beyond lacerations).  There are people who will LOOK for that "tsuchi aji" (Japanese term .... "clay flavor").

 

As to the subject of coasters...... we have numerous types in the house.... including actual chataku.  In the Japanese tatami room we have in our house, when we use the low table, yunomi,( even with very smooth bottoms) always get coasters. 

 

best,

 

.......................john




#89549 Yunomi

Posted by JBaymore on 25 July 2015 - 09:10 AM

Grype,

 

Look at the foot on that Lisa Hammond.  It has been ground..... you can see the grinding... from the color change in some areas.

 

So looking at the "traditional" heritage ......... there are a LOT of factors that come into play.

 

1.)  If you were Japanese in days not all that long ago, and you were served a brewed tea of some sort (like sencha, genmaicha, mugicha, etc.) in a yunomi form, you would be sitting seiza (siting with your butt resting on your feet.....sort of kneeling) on a floor made of tatami mats.  The cup would be placed on soft tatami mats.  The foot of even the roughest pieces would not be an issue in that situation.

 

2.) If you were (and are) a Guest being served tea in a yunomi, it is going to be placed on a small (usually) unfinished wooden saucer called a "chataku".  This act honors both the Guest and the pot, and protects anything under the chataku from possible damage. 

 

3.)  In general, Japanese people tend to pay far more attention of the activities they are involved in, and so are more aware and careful of how what they do can and does affect others.  So using a rough bottom cup in such a way as to damage furniture would be kind of unthinkable to them.  The sixties phrase "Be here, now" comes to mind...... but the Japanese don't usually need reminding of that important idea with a slogan.

 

4.)  The Japanese in general have a distinct love of nature and the natural world.  The materiality factor in clays that have not been overly refined is something that it often found desirable.  Any risk of scratching is far outweighed by the beauty of the clay.  In fact the texture of the foot against the left hand as it is cradled there is an aesthetic PLUS... not a negative.

 

It is complex.  I could write a book.

 

Changes in lifestyle in Japan have had their impacts.  I have been told by potters that there was a law passed not all that long ago that specifically made a potter liable for any damages that a pot foot caused to furniture.  I've not see the law....... but I believe that it is accurate information. 

 

But what they might consider "smooth" is a bit rougher than likely what U.S. potters might think.

 

best,

 

.....................john




#89510 Designation--"Master Potter"

Posted by JBaymore on 24 July 2015 - 09:51 AM

And furthermore, in many cases, they value things, they don't actually realize are Art, or exist because of Art/ Artists.  

 

Amen.




#89382 Am I The Only One Who Has Spent Hours Trying To Log/ Sign In?

Posted by JBaymore on 23 July 2015 - 07:36 AM

KM4IHN DE KA1HLI ........ 73  :)