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#93258 Adventures Of A New Wheel Teacher

Posted by JBaymore on 26 September 2015 - 09:50 AM

My love affair with clay got off to a rocky start due a teacher who made a big deal about me being left handed.  



In my opinion, the more important hand in throwing in the Western rotation direction (counterclockwise) is the inside hand.  Make the inside well......... the outside will follow.  Left handers have great control of the inside hand.  Righties need to learn to use the other one ;) .  (FYI... a rightie that, after 45+ years of claywork, is now a bit ambi.)





#93161 Qotw: Have You Ever Taken A Video About Yourself, Showing How You Work?

Posted by JBaymore on 24 September 2015 - 09:40 AM

Relative to photos and videos and such.........


How websites perform can be affected by the BROWSER that someone is using to access the content.  Even huge businesses have issues this that sometimes (example- for one of my banks I have to use one browser to access anything...... the other does not function correctly).  Then there are also the user's settings within any given browser....... Flash.... Java... and so on.


So getting a typical individual potters website automatically "synced up" with all the possibilities of browser and screen format access, including the common mode for the aaaahemmmmmmm...... "younger generation"....... (smartphones and tablets) ...... can be an issue.


Most of us are too busy being potters to learn all that is needed to be a true "webmaster".





#92885 Production Tips For Production Potters

Posted by JBaymore on 19 September 2015 - 09:28 AM

You can also build what amounts to a large "egg slicer" to cut pugs automatically all at once with only one or two moves.


This approach can also be done to make small slabs out of a full 25 pound rectangular slug.





#92828 Satin Matte Black Cone 10 Oxidation

Posted by JBaymore on 18 September 2015 - 10:12 AM

The first task you have in this pursuit is actually defining what YOU mean by "food safe".


There is no "legal" definition (in the USA) of that term, even although potters tend to toss it around like there is some single ASTM standard for it.


What you are basically looking for is physical durability and chemical stability of the fired surface.


Within that above criteria, a semi-gloss surface and also a black color.


Physical durability, chemical stability, and black is not all that difficult.  It is that "semi" surface part that brings in the potential issues.  It is like you can easily have three of the four...... pick the three you want the most ;) .


For getting the black color...... use a commercial glaze stain not a super saturation of metallic oxides.


For durability and stability... get the silica number as close to upper molecular limits as you can, as well as also maintaining high alumina numbers.


Not saying it can't be done.... just that it is not easy. 


Lots of testing work coming up for ya'.  Including lab leach testing.





#92787 Matte To Gloss Glaze Chemisty With Al2O3

Posted by JBaymore on 17 September 2015 - 04:48 PM

Building on Neil's comments........


Partilcle size is one raw materials SOURCING issue that (as I mentioned above) does impact the way that glaze melts.  Depending on the firing cycle this can change the end result if the glaze is not allowed to fully come to (technical) maturity (which a LOT of our glazes are not allowed to do).


The "best" places to start with supplying oxides are in raw materials that already have the components in intimate and often molecular sized contact.   Compared to even the finest grains of 325 mesh silica, the silica molecules that are already associated with alumina and fluxes and so on in a particle of feldspar will be affected by the nearby flux materials WAY before that MASSIVE grain of "pure" silica. 


You can think of it as "the small stuff melts first".


So you'd want to source the alumina from other materials first.  It is only if you can't get enough alumina into the mixture in that way that you'd result in using something like aluminum oxide or alumina hydrate powder.


When a kaolin (any clay, actually ) is heated there is a change that happens called "silica ejection" when it becomes what is known as meta-kaolin.  Those "bits" of silica are literally single molecular size.  They are very reactive with any fluxes present. Getting some of the silica in a glaze in this way is preferable to adding ground quartz rock. 


(This is also one of the reasons for dunting in clay bodies that don't have enough glassy phase.... those tiny ejected crystalline silica molecules convert very readily to the cristobalite form.)





#92650 Qotw: How Far Would You Travel For A Show/a Workshop/an Exhibition?

Posted by JBaymore on 15 September 2015 - 09:04 PM

I have never had a solo show ... Now that I would go anywhere for!


Wow...... that is the world's loss.  If anyone deserves that kind of recognition.... it is you Chris.





#92609 Qotw: How Far Would You Travel For A Show/a Workshop/an Exhibition?

Posted by JBaymore on 15 September 2015 - 11:39 AM

Let's see... solo and group shows and pieces placed in museums in Japan, China, South Korea........ so about as far away from home as I can get.  About literally 1/2 way around the world.  (Haven't circumnavigated yet ;) .)


In fact, headed to People's Republic of China in about 3 1/2 weeks for presenting at a symposium and a show ....with students in tow.


The world has shrunk in the last 20 years.





#92572 Qotw: Are "kiln Gods" Superstition?

Posted by JBaymore on 14 September 2015 - 07:45 PM

But when it comes down to it, the only force that has any impact.......................


Reach out with your feelings.  Your eyes can deceive you. ;)





#92348 Cobalt For Brushing Recipe?

Posted by JBaymore on 10 September 2015 - 08:55 AM



Man... your work there in the image looks a lot like Hamada Shoji's.  ;)


Hamada's slightly grey-ed out blue there is based on something called gosu... which is an impure source of cobalt.  The ground rock also contains a bit of manganese dioxide and iron oxide and some fluxing materials.  The gosu is a very fine mesh material when used for this (as well as for overglaze enamel use). The finely ground gosu powder is typically blended with a thickened mixture of a green tea extract (make strong sencha type green tea from leaves, let it sit 'forever', then boil off some of the water) that lends it brushing consistency and acts as a kind of "fixative" when it is dry.


For the following, note that I an working high fire.... cones 9 to 14.


As far a the stuff I use here in the US, I also use cobalt carbonate as the starting point of a mix rather than cobalt oxide.   Typically the carb form is a finer particle than the oxide from US suppliers.  Then to that I add a small amount of Cedar Heights Redart to add a trace of iron into the color mix, to supply a bit of flux, and to also enhance the suspension and brushability in the wet state.  Then comes a pinch of manganese dioxide for the color rendition (takes the "harsh" out of straight cobalt compounds).  Then a tiny bit of frit 3124 as more flux.  Add water.  Then I also add some glycerin to make it all brush better.


For the stuff that gets brushed on top over a raw glaze coating, I also add a tiny bit of white wood glue.  This causes the "dust" to set when dry and not get smudged in handling when stacking.  White wood glue burns right off and leaves no trace.  If you do this you have to keep the material in a covered container when not in use.


If you try this kind of mixture, to get the ratios of the coloring sources correct, you'll have to test to your own tastes in the blue you want to achieve.





#92098 Qotw: Do You Strictly Observe The Safety Rules In Studio?

Posted by JBaymore on 07 September 2015 - 09:55 AM



Read through this LABROTORY type Material Safety Data Sheet for general background from the scientist's views on handling this material:




A lot has to do with the particle SIZE of the manganese dioxide (black manganese) that is included in that body. Big (relative) stuff does not get airborne easily.  It is what is known as "the fines" in the material that are likely problematic for developing any airborne dust issues. 


As to ingestion, likely not an issue for you since you know what you are doing in a studio.


I think the 'interesting' part of this information is the skin contact information.


What is very "interesting" is how the above science oriented information compares to the following "studio ceramics" MSDS for the same material:




An important thing to keep in mind when reading MSDSs is that the production of an MSDS by a company is done at the direction OF that company.  The formal governmental/legal review process of those MSDS documents in the arts field is, according to a source who should know, not all that rigorous.  I've seen MSDSs from some places that are so lacking information they are laughable.  But no one "calls" them on them.


So ......... caveat emptor.


Main issues with manganese dioxide are "chronic" ....meaning repeated long term exposure to even low levels.  Just a total guess here from a non-medical person.... but I think 4 weeks does not qualify for worrying too much.  :)


If I had to venture an educated guess on if it is MORE hazardous than a white or light body....... I'd have to say "yes".  BUT... and that is a big "but".......... likely statistically a small amount more. 





#92004 Qotw: Do You Strictly Observe The Safety Rules In Studio?

Posted by JBaymore on 05 September 2015 - 10:36 AM



I've been doing workshops, consulting, and teaching for a long time.  I've visited many potters and schools studios over the years.  From what I've seen...... a 'dose of awareness' is certainly still important to get out there.  Even today.  Some of the practices and working conditions I've seen, even quite recently, make me cringe.


So your interest in getting folks to be aware is not misplaced at all. No apology needed. 


Like Mark, I remember my early days at the University when I was in school......... mixing clay from dry materials in a closed room that was barely big enough for the paddle blade batch mixer (no safety shutoff or lid cover) with no ventilation.  One very small window open, no fan.  We tied a cotton scarf over our faces to help with the dust. Raku-ing with raw lead glazes... and cooking food over the kiln's exhaust.


We've mostly come a long ways from that time in the 60's with the awareness about health and safety.... but I still see practices way too often that are not all that different from "the good ole' days".


The levels of exposures for most of us, even full-timers, are typically far lower than the experiences of people like miners and heavy industrial workers....the people that "the studies" usually look at.  But the big issue usually is that we typically don't know the level that we ARE being exposed to.  THAT is the real issue in this subject for the studio artist.  So we tend to have to go 'a bit overboard' from the likely reality to try to make sure that we are protected.  Most of the time... we likely are OVER protected.


Over-reaction happens.  People who 'go off the deep end' and feel that with a single speck of XXXXXXXXX (pick your poison) in the studio... and we are all going to die.  There are few toxins that a single speck is going to do you in.  ;)  (Maybe anthrax spores or something like that fits that bill.)


Yes, there are hazards in using stuff like barium carbonate, manganese compounds, uranium compounds, arsenic compounds, cadmium compounds, flint/quartz, and so on.  But if folks take the time and invest in themselves and their health enough to educate themselves about the nature of the dangers, and the ways to mitigate those dangers....... then working in the studio and not killing yourself in the process is still very much possible and, in fact, quite likely.





#91966 Qotw: Do You Strictly Observe The Safety Rules In Studio?

Posted by JBaymore on 04 September 2015 - 11:39 AM

Chris nails it (yet once again). 


Anecdotal evidence is suspect.  Be wary. 


When people get sick... they are always looking for a "reason".  Sometimes they make incorrect conclusions.  Another factor..... people who are sick often want to remain very private about it... and do not "advertise" that fact... so you don't ever even hear about it.


Also there is something called in the field "genetic predisposition".  Yup..... some folks can smoke 10 packs of cigarettes a day and also drink a whole bottle of whiskey every day... and die while skydiving at the age of 104.  Others can look at a certain carcinogen... and get cancer a few months later.  (We tend to hear about the former... not the latter.)  If you don't know your personal situation in that regard...... well....... it's a crap shoot. ("Do you feel lucky, punk?"  -Dirty Harry)


There is a LOT of information on this H+S stuff published.  Some highly technical.  If you haven't availed yourself of the information....  you still can.


The three easy to read references from my ceramic toxicology section I teach at the college:


Arist Beware  - Dr. Michael McCann


Keeping Claywork Safe and Legal  - Mononna Rossol


The Complete Artists Heath and Safety Guide  - Mononna Rossol



Chronic manganese poisoning is linked to a condition that very closely mimics the symptoms of Parkinson's Disease.... not ALS.


I personally know 5 potters that have diagnosed silicosis.  They did not work in mines, changing auto brakes, and other such known risk situations.  Likely cause.... ceramics related.  100% provable.... can't be done.


I also know one well known long term potter with diagnosed (and being treated) lung cancer (which also can be caused by inhaled silica exposure).  But linking that case directly to ceramics is not something that medical science is able to do with 100% accuracy.   Could it be related.... yes.  Could it NOT be related.... yes.


I've personally had a few ceramics related occupational health issues.  This stuff happens.  Nothing fatal...... so far....... I'm still kickin'. 


I'm very aware of the subject and take precautions in the studio.  Basic stuff is really pretty easy to do and be effective.  I do not "seal myself in a baggie".  I also do not throw dry clay and glaze chemistry around.  This is an important subject.... but there is a lot of "hysteria" that goes around in the community about it.


Get yourself educated. 





#91826 Qotw: What Do You Think Of Art Critique?

Posted by JBaymore on 01 September 2015 - 06:33 PM

In critiques I do at the college, using the words "like" and "love" are off the table.  Also the negatives of those terms.


We also focus on the fact that the word "critique" does not automatically imply a negative context to the process or the comments.





#91730 Liability Shift On Cc Coming Oct 1, 2015

Posted by JBaymore on 30 August 2015 - 11:02 PM

.............. which I try to not use because it reduces the young labor market drastically.


I also try to not use self-checkouts anywhere for the same exact reason.





#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.