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JBaymore

Member Since 06 Apr 2010
Online Last Active Today, 08:58 AM
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#58959 Problems With Plasticity

Posted by JBaymore on 21 May 2014 - 11:58 AM

Interesting and lofty goal.

 

Years and years and YEARS ago I did consulting work on the reconstruction of a true-to-period updraft collonial era earthenware bottle kiln for the living history musuem Old Sturbridge Village in Massachusetts.  It is a recreation of a colonial village.  Quite large.  It was a fascinating place... everyone was "in character" and in costume. Lots of traditional crafts..... raising sheep to get wool that was carded and spun into yarn, dyed with vegetable dyes, and so on.  Craft work and food sold to the visitors.  The pots they made in the pottery there were sold in the museum gift shop.

 

We used hand made bricks made by a local brick plant to build the large kiln (Turns out that the person who made those bricks -Kurt Heinzman- years later ended up taking pottery classes with me at NHIA!  We didn't know this common relationship until much later).  The bricks were hand struck and burned in ricks.

 

https://www.osv.org/pottery-shop-kiln

 

https://www.osv.org/...ery-kiln-firing

 

At the first firing there I remember that we need to make a sort of a metal flap for the air intakes to control the air flow better.  I had to send a runner across the village to contact the 'village smithy' across the museum grounds, and he had to then hand make the parts we needed to be totally "in period".  Took a good while to get that as we were firing.

 

Made you appreciate the conveniences of stuff like telephones and readily available manufactured goods.

 

The reason I relate this story here............ behind the scenes..... and behind closed doors....... there was a room full of modern electric kilns.  They also were using a non-raw-lead commercial glaze on the redware.   And while they had a publicly viewable clay pit and were doing tradional proccessing there, the earthenware clay that they really used for production was from Cutter Ceramics (the "Laguna" of that time ).  I think I also remember some electric wheels behind the scenes (been a LONG time.... memory fades).

 

Being totally traditional is tough.

 

best,

 

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




#58604 Strong Bleach Odor In My Bag Of Laguna Clay

Posted by JBaymore on 15 May 2014 - 09:45 PM

My guess is that the clay was very old.... and covered with mold. And someone decided that the way to not have the customer buying it complain or go "oooooohhhhhhhh yuck".... was to drench it in bleach.

 

Just a guess.... but it is the only thing that makes any sense. At least to me. But what the heck do I know.

 

I would have taken it back instantly. They killed off that good mold ;) .

 

best,

 

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




#58580 Why Is Our Work Better Than Imported Work?

Posted by JBaymore on 15 May 2014 - 03:09 PM

There are many days that I honestly do not know where I am along the good-better-best cycle in the clay world.

Me too. I'm just chasing that "mechanical rabbit" that always seems to be somewhre out ahead of me. Don't expect that I'll ever catch it. The importance is in the active pursuit... not stopping :).

 

best,

 

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




#58561 Why Is Our Work Better Than Imported Work?

Posted by JBaymore on 15 May 2014 - 11:49 AM

On the other hand, I'm afraid I see a lot of potters who are struggling to sell. Tact prevents me from asking "do you think it might be the mustard yellow and green glaze combo?"................

 

Thanks for addressing the 900 pound gorilla in the room. I applaud you going out on this limb with your comments. 'Political correctness' often prevents useful and honest dialog and critique, particularily in places like online forums. Too bad really. It limits the effectiveness of that kind of venue. And it doesn't help improve " the field".

 

Good pots is good pots. I also often come back to the old Alfred comment: "A pot without a soul is just clay around a hole".

 

'Our work' is only better than 'imports'.... when it actually is better. Far too often... it is not. Skilled handcraft is functionally and aesthetically better than unskilled or poorly skilled handcraft. Unskilled or poorly skilled handcraft is not necessarily functionally or aesthetically better than mass produced work (heresy! :P ).

 

Here's the really hard and politically incorrect statement coming: Too many people want to start being a "professional" in the ceramics field way before they are really ready to do so.

 

Since there are no standards that prevent this from happening, and "free enterprise" tends to rule (at least in America)....it is very easy to do this. In "years gone by" I think folks tended to self-censor such inclinations much more than they do these days. More folks would not even consider 'hanging out the shingle' until they had spent a lot of time learning the craft to a pretty high level of technical and aesthetic skills. These days.... two community ed classes, and the financial ability to buy a wheel and a kiln... and bingo.... instant professional potter.

 

This practice is hurting the whole field.

 

Personally I always return from Japan, Korea, and China feeling incredibly humble and a 'babe in the woods' when it comes to my own knowledge and skills in working with clay. You can only understand the broad level of ceramic skill that resides in those cultures with such huge histories in the field...... by having the chance to see them first-hand. And I've been doing this full time for 40+ years, and have been teaching it for almost as long.

 

There are some darned nice "imports" being made and imported. Alluding a bit to that CapitalOne credit card TV commercial...... "What's in your kiln?"

 

 

best,

 

 

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




#58521 Are Dinnerware Safe Glazes Safe?

Posted by JBaymore on 14 May 2014 - 04:31 PM

Pet peeve of mine here........

 

There are a lot of people making and selling pots for food usage that have no idea about the technical side of things and have no real idea if their product they are selling actually is "food safe".  So just because you see something being done does not mean that is is "researched" or "good" or whatever you want to call that.

 

Worst part of this whole issue is that the term "food safe" is basically a meaningless term, and not defined by any regulatory body.  The US FDA has legal standards for only the leaching of lead and cadmium out of glazes..... nothing else.  And those stadards are not limitig a glaze from CONTAINING those oxides... just the leaching of them.  (Many commercial dinnerware glazes still contains lead.)

 

The manufacturers do not indemnify the end user for the use of their product in the making of work for sale.  That means... it is up to YOU to know if the glaze is safe to sell for food useage.  You hold the liability and the responsibility.  The only way you will know is to forumlate a testing regimine and operform the "due dilligence" to figure that out.

 

Note that if a glaze does not contain any potentially toxic ingredients... then it does not matter if it leaches (from a liablity standpoint).  But using commercial glazes....... they will not give you the recipe or formula... so you don't know.

 

This subject comes up a LOT here.  See the FAQ listing at the top of this forum section about "is this glaze food safe".  Lots of good info on there to read. 

 

best,

 

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




#58485 Pinhole Doctor Needed – Nasty Case – Diagnosis Required.

Posted by JBaymore on 14 May 2014 - 08:18 AM

I ran the glaze as best I can (Soda Spar and China Clay are way too 'generic' for much accuracy in calc) and it came out within limits for the general end point temp you are running (extrapolated to a cone).  As Neil said...... it is high in soda (but in limits)... but that could be because of the generic "soda spar" used in the calc.  And the alumina is just under the top end fior alumina,  but within limits.

 

No active vent on the bisque kiln (no good airflow) and the fact that it happens heavily on this clay and not on most others, that it happens more on the lower (contained to bisque air flow) parts of the forms, all make me suspect bisque issues. 

 

Yes the glaze will be "stiff" due to the high alumina..... which if pinholes are forming... will tend to prevent their healing over for SURE.  So it is very much possible that a bit higher cone end point will allow them to heal over.  But it would be interesting to see if that problem can be fixed by not having them develop in the first place....... which MAY be coming from the lack of organics being burned out at the right time in the bisque, and continued outgassing of some other reactions.

 

And you should really be using cones in the load to control endpoint ......... not just a temperature on a thermocouple.  The thermal lag between the thermocouple ptrobe outin the open and the considion of the wares back in the load can vary a lot based upon the stacking density.

 

best,

 

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




#58438 Developing A Cookware Clay Body

Posted by JBaymore on 13 May 2014 - 12:01 PM

It seems to me that the issue here is answering the question, "How much risk are you willing to accept?"  For me, flameware is on the pernament "no-no" list.  Oil lamps are also on the "no-no" list and always have been. (Could have made a FORTUNE back in the day!)

 

For me personally there are two categories of "risks" involved: 1.) Ethical standards risks.  2.)  Legal liability risks.  Unfortunately, niether has easy answers. 

 

I'll deal only with #2 here.

 

The problem with the "do not put in preheated oven, allow to cool naturally" approach is that the description needs to stay with the piece for the useful life of the piece to help protect both you and the user.  Paper additions get lost.  Legally... I'm guessing that a sharp lawyer would contend that you should have expected that would happen to the paperwork and if the admonition was truly necessary, made provisions to warn all the users of your product not just the original sale owner.  Hang tags and product inserts DO get lost.

 

My own personal attempt at a type of solution to this liability issue a while back was to have a stamp made that said "Do not burn unattended." for some incence burners I was making.  Unfortunately that stamp on the bottom looked like crap, and tended to move the feel of the work from that of "fine craft" toward that of "commodity".  Not the idea I want with my work.  Difficult.  Fix one issue... create another.

 

Another factor in the "legal liability" side of things is how much you actually have to lose.  If you are literally a "dirt poor" (pun intended) potter......... even if someone is harmed by your product..... the liklihood of getting sued for damages is kinda' small.  To quote Janis, "Nothin' from nothin' leaves nothin'."  Such liability suits are usually "contingency fee" based, and a lawyer will usually only take one on if they see a reasonable paycheck possibility.

 

But if you are a bit more affluent, maybe because pottery is a second job to the 'big money' job, you are retired from a previous well paying career and are now doing pottery, your spouse has a high paying job, and so on... that is potentially a very different story.  Unless you are a corporation, (like a LLC) then the assets that you (and your spouse) have (homes, stocks, all studio equipment, etc.) are at risk in any potential liability situation.  Even if you "have a business" and file a Schedule C.  A sole propietorship does not protect personal assets.

 

Some would argue that having liability insurance will attract the contingency lawsuit.  A valid thought.  Again.... no easy answers.

 

If you are concerned, at the minimum get yourself product liability insurance.  The Potters Council has it for members (plug, plug, plug ;) ).  ACC has it for members.  CERF has it for members.  Any insurance agent can get it for your business.  If you are typical, it'll cost you less that $1000 a year.  Cheap really for the protection and peace of mind.  And maybe look into setting up a LLC for your pottery business; it is not hard and not expensive.

 

As to the technical side of the bakers......... you have to test them .......a lot.  Don't assume.  Do the "stupid stuff" that a consumer likely will do with it and see what happens.  They will.    Take it out of the dfreezer and put it in a pre heated oven.  Someone will.  It is for THOSE people that you have the liability insurance B)

 

best,

 

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




#58421 Developing A Cookware Clay Body

Posted by JBaymore on 13 May 2014 - 09:52 AM

I've personally seen the low expsnsion body "crack with some force" on a flame.  Not like the pre-stressed stuff though.

 

Mythbusters did a segment on the pre-stressed glass and plastic laminate side window panels on an automobile.  Interesting stuff.  They too literllay explode into tiny rounded-edge granules when hit just right.  Designed to do that to prevent sharp flying glass in an accident.

 

The real issue with flameware from the lability point that I personally see is not that it is going to suddenly "explode" with severe violence like a fragmentation grenade (the Pyrex can).  It is that it is going to be filled with very hot foodstuff in a working kitchen environment, and that it is prone to unexpected cracking due to the uneven thermal stresses. 

 

When that piece fails as it is being moved / carried, all of that hot, scalding, burning, foodstuff is potentially going to land on the cook's arms, legs, or body, on the 2 year old child under their feet, or on the much-loved family dog or cat.

 

Aside from the moral concerns involved.......... can you say "lawsuit"?

 

We certainly have the same potential risks with any food service item that we make.  A handle can come off of the cup of hot coffee at just the wrong time.  (Remember the McDonalds lawsuit... something like $4 Mil because people -of course- would not expect that hot coffee is............ hot.)

 

But the quality control over the production for flameware adds in a whole extra level of serious technical complexities.  Technically correct body formulation, accurate mixing operations of that body, precise forming operations as to thickness and stresses set up in that part of the process, accurate glaze thickness application, and precise firing. 

 

While all of the SAME things above apply to other types of food service wares for consistency of product....... we don't then try to stress the living crap out of them over a direct application of flame to part of the piece.  Typical food sercvice clay wares are not as "touchy" as flameware, and do not have to tolerate the same extremes of environment.

 

Just seems to push the risks too high for my taste (and liability tolerance).

 

best,

 

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

 

PS: Benzine..... yeah.. I think I did.




#58369 Pinhole Doctor Needed – Nasty Case – Diagnosis Required.

Posted by JBaymore on 12 May 2014 - 11:55 AM

Pinholing is probably 90 percent caused by bisque firing and clay body issues... not the glaze or the glaze firing.

 

Please describe in more detail your bisque firing process....... what is the cone that is down?  What are the rates/ramps. etc.  Do you have a local pickup (downdraft) VENT on the kiln?

 

What types of forms does the pinholing happen more on (if is tends to do so)?

 

Does it happen evenly on pieces that were stacked in all areas of the bisque kiln... or more on pieces from some locations?

 

Worse inside or out, or pretty even?

 

Any other glazes doing it?

 

Does the same glaze do it on a different body?

 

best,

 

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




#58278 Need A Cheap Simple Clay Body Recipe

Posted by JBaymore on 10 May 2014 - 09:19 AM

Joseph,

 

As to educatiing a "well rounded potter", I am all for learning about making clay bodies from scratch.  I teach about that activity in my college classes.  BUT I also spend time teaching about ceramic toxicology.  And the concept of "transference of risk" is something that gets stressed for that "well ropunded potter" also.  Knowing when it is time to contract out some activity that you cannot set up to do safely in a cost effective manner.

 

Maybe think of making your own clay from scratch for a limited production kind of work.... with the body being distinctive and "special" (and the pieces costing more becasue of that to pay for the labor and risk and uniqueness)... and leave the bulk volume general production body mixing to a commercial supplier. It can still be your own recipe they mix up.  Only spend the time and risks needed to develop the body to your liking in relatively small  amounts (hundered of pounds per test batch)....and once it is "there'.......  then contract out the mixing work to a place that is equipped to handle the stuff relatively safely.  The minimum order is usually 2000 lbs.... which for someone doing serious production work...... is not that much clay.

 

The health hazards for the potter go up exponentially with stuff like bulk clay mixing from dry commercially prepared ingredients.  "Folk potters" never had as big an issue because the raw materials they they used to mix the clay were not commercially "beneficiated".  The bagged dry materials we get are produced mainly for industries OTHER than for wet clay pottery making... and the fine-ness and particle size distributions of the powders is WAY more easy to get airborne than our pottery ancestors ever dealt with.

 

I know a number of potters with diagnosed silicosis... and I know at least two with lung cancer.  Of course... anecdotal evidence here....... could have nothing to do with their clay work..... but then again......... .  Clay (and other silica-bearing ingredients) are KNOWN human carcinogens.  And also are KNOWN to cause silicosis.  We can't get away from ALL of the risk......... unless we stop working with ceramics........ but we can minimize it.

 

The cost to set up local pickup ventilation systems in an interior space that will control the dust to keep it below OSHA/MESA PELs / TLVs will be VERY expensive.  Makes that "cheap" clay very expensive (unless you go into commercial production.... and then the per pound cost over thime and volume will come down to reasonable levels). 

 

The alternative is to risk your health..... which is also very expensive.

 

As a wood firer, I'm one who is all about the "process" too....so I understand the allure of making your own clay.  Doing it all in more involved and maybe primitive (by today's standards) ways is seductive.  And I do make the "specialized" bodies myself (in limited amounts).  But I also have a decent small scale mixing and local pickup vent system....that was put in 35 years ago when you could do such stuff far more affordably. 

 

But when you "cut to the chase"....... REAL potters just make good pots.

 

best,

 

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




#58248 The Dangers Of Advice Without Experience

Posted by JBaymore on 09 May 2014 - 11:54 AM

For what it is worth...There is another active thread on the forum about dry skin caused by clay, glaze, etc. Biglou made an interesting observation. There are M.D.s on the forum, yet none have given their advise about ecczema, psoriasis, or contact dermatitis therapies as they relate to ceramics.

I am a praticing M.D. who treats these condition on a regular basis. Before I could diagnose I would need to gather a better history, view the lesions and review med usage, etc. The forum may not be the best place to do this.

BUT, It is a great place to take a history of ceramic problems, view pictures of the problem areas, review glaze usage and application, and diagnose/discuss remedies to the problems.

I appeciate and thank the "Clay Doctors" of this forum for sharing wthout restraint.

Jed

 

 

Jed,

 

Well said.

 

And your comment about "Before I could diagnose I would need to gather a better history, view the lesions and review med usage, etc. The forum may not be the best place to do this" is precidely why I start so many responses with the "It depends" business that is my trademark in my college classes and also here.

 

So there is some 'restraint' there.

 

And just like in the area of medical practice...... a forum like this has severe limitations in "diagnosis and treatment" of ceramic issues. For the "glaze and kiln doctors" you also typically don't get the full history, you can't get a "hands-on" viewpoint on the material or equipment in question, you can't order accurate lab tests yourself, you have no idea of the level of 'technical' understanding of the person with whom you are working, many of the terms we use are 'subjective' in meaning (such as "put the kiln in reduction" versus the numbers you'd get on a crit) and so on. Not much different from the MD's problem with medical related stuff from 'afar', really.

 

Hence... somtimes.... 'bad' advice on things.

 

It is also why when it comes to all the health and safetty discussions that crop up... I routinely tend to refer folks to the published "primary source" references in the field...... and tell them 'talk to your doctor'. And for the "is it food safe" stuff......... constantly tend to say 'get it tested and then compare to published standards'.

 

And why I said earlier in this thread.... "Vet your sources."

 

I've seen so much stuff published on forums, in magazines, and in books that, at the least, goes 100% contrrary to basic science it is amazing. But it is often politically incorrect to point out that "The Emperor has no clothes".

 

 

FYI........ here's the bottom line disclaimer included on the college level class texts on ceramic toxiclocgy I've written:

 

"NOTE: This document was not prepared by a health care professional, and in no way constitutes medical nor legal advice. Please consult a qualified physician with your concerns about any of the health issues discussed in this paper, and a legal counselor for any legal issues discussed."

 

best,

 

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




#58181 Frustration Finding A City Workspace!

Posted by JBaymore on 08 May 2014 - 03:44 PM

As a kiln designer and builder.... you can still often get them in. It is just harder (read more expensive) now.  You have to know how to "talk their talk" and not come across as a "potter".  Package stuff up like a developer or a contractor.  Lots of slick paperwork and the right exact terms.

 

And do note that SOMETIMES all of those expensive regulations and safety stuff are things that too many of us have gotten away with not having for far too long.  There HAVE been some nasty issues with kilns.  But surprisingly when I did a study about "kiln disasters" a good while ago... the number of ELECTRIC KILN messes was REALLY large (yes... there are more electric kilns installed than gas kilns.)  Electric kilns often get installed really poorly, and often routine maintenence is sorely lacking.

 

Much as I hate to say it I often advise a client hitting the brick walls to get a Bailey of a Geil now. They are both AGA certified... which drops a HUGE amount of the "hurdles". But you are paying for that nice AGA certification; a lot less kiln for the buck than a site built unit.

 

best,

 

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




#58164 Carbon Trapping?

Posted by JBaymore on 08 May 2014 - 01:06 PM

Nope Timbo....... there is so little carbonaceous material in the average clay body that it is not really going to have all that much visible effect.  Screw up a body from reduced iron becoming a brittle low temperature flux on silica within the walls.... yes.... but doing much coloring on the exterior surface even under a glaze.... not really.

 

A clay body will "carbon trap" like in Lou's case even without a glaze on it in a wood kiln due to the (frequently) really poor mixing of fuel and air, and the high level of microscopic carbon particles floating about... combined with the volitiles from the wood ash (like potassium and sodium) that "fume" the surface of the clay...and perform much like the soda ash deposits on the surface of shino glazes.  The typical difference in an extended wood firing is that this deposition can happen for much longer periods in the wood kiln which can even include toward the cooling cycle side of things as embers burn off, surfaces are still fuming with volitiles, and airflow is cut off.

 

If you've ever saw Malcolm fire his serious carbon trap shinos..... the level of soot smoke coming off the kiln at really low temps was more akin to an anagama in reduction than the typical gas kiln firing most of us think of "in reduction".  Choo choo train stuff.

 

best,

 

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




#57999 How Much Pots Would A Potter Pot If A Potter Could Pot Pots?

Posted by JBaymore on 06 May 2014 - 01:14 PM

20 pots a day, five days a week at $30 average per pot is $156,000 worth of pottery a year. I would offer that for a good potter the issue is marketing not production.

 

Cutting to the chase. Only 100 relatively inexpensive ($60 retail) pots a week, consistently.

 

Food for thought.

 

best,

 

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




#57921 Handles

Posted by JBaymore on 05 May 2014 - 08:54 AM

And I really do think it's not just about practicing. Analyzing pots as I drifted off to sleep, dreaming about that perfect handle, visualizing it before I headed to the workshop ... All of it is working. It's working!

 

There is the saying and myth that everyone seems to 'know'; "Practice makes perfect".

 

Unfortunately it is not a true statement as it sits.

 

Repetitively practicing something like a motor skill activity which is being done poorly simply ingrains the poor performance and makes it harder to change the movements later. INFORMED and CONSIDERED practice moves your performance toward what might be called "perfect". This means being 'in the moment' and analyzing what you are doing with each subsequent repetition to improve on that last performance. If you can't figure out how to change things for more successful outcomes, that is where the help of a teacher comes in.

 

Mindless practice (repetition) really doesn't help when you are trying to develop a skill. (What is that definition of insanity........ doing the same thing over and over and expecting different results.)

 

best,

 

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