[Clayart] slow bisque

Thu Apr 4 15:05:41 UTC 2024

Thanks, Vince.

The convection idea is a lot like one I've had too, and will be the project if the vacuum doesn't work.

In a past life, I was a vacuum technician and, like algebra, I like to find ways to make that part of my life a part of this phase. But It occurs to me that the next best way would be warm air moving the moisture through convection, assuming the vacuum works, and the best way if it doesn't.

In my imagination the problem with fast drying, not counting warping and other gross phenomena, is the rate the water migrates to the surface, relative to the pressure pushing it. When is water steam and when is it water vapor? I would say that above 212f it is steam. Then the question becomes: Is there a difference between steam migrating out of a body and water vapor migrating out? And then, water cannot be heated above 212 (100c), but steam can, so is 350 deg. steam less destructive than 550 deg. steam?

And, do the particles pack differently at high rates of outgassing, such that instances of microfractures increase?

As a rule, these ideas of mine don't work out. When they do it can be cool as hell, but usually they don't. Still, I'm going to try this since I have a theory that I can more precisely regulate the rate of outgassing when it is under vacuum and at the same time pulling water from the object in a 360 degrees of effect sense, as opposed to upward only movement, meaning closest earlier than the furthest effect which creates a differential between the size of the near face and the size of the far face (that is probably unintelligible, sorry).

On a fun side note (I'm easily distracted), I do my f to c conversion by multiplying or dividing by 1.8 and adding or subtracting 32. So 100c x 1.8, is 180, plus 32, is 212. As I was writing the above I realized a possible point of confusion between degrees temp and degrees in a circle. In Fahrenheit it is 180 degrees from freezing to boiling, half of a circle. So the mind went to, "What is a degree actually." I joined Silver Sneakers last month and need to get this as a habit, so I need to get out the door and I shelved learning what a degree is for the moment (pass it along if you know), but I had a hunch that if I divided 360 by 1.8 I would get a whole number, and I did, and it was 200. And, yeah, I had a duh moment since that should have been obvious, since 2x180 is 360, lol.

Joel.
________________________________
From: Clayart <clayart-bounces at lists.clayartforum.com> on behalf of vincepitelka at gmail.com <vincepitelka at gmail.com>
Sent: Thursday, April 4, 2024 5:28 AM
To: 'Clayart international pottery discussion forum' <clayart at lists.clayartforum.com>
Subject: Re: [Clayart] slow bisque

About a zillion years ago, I had graduated from Humboldt State and was working as a mechanic for the City of Arcata while getting my first pottery studio going in Blue Lake, California.  A friend who was currently in ceramics at Humboldt told me encouraged me to attend a slide lecture to be presented by a visiting potter.  I wish I could have attended his demonstrations, but I had never heard of him and knew nothing about him, and I was busy with too many other things.  The potter's name was Tom Coleman, and this was back when he was still living up in Oregon, before he moved to Las Vegas, but after John Nance wrote the book about him, "The Mud Pie Dilemma."  Coleman's lecture was inspiring, and influenced some key directions in my work at the time.  In addition to talking about his own work, Coleman discussed and showed slides of other Oregon potters, including Joel Cottet, who unfortunately passed away in 2002.  Cottet was a former football player who made huge pots, we are talking about giant planters, garden tables, hot tubs, and huge garden lanterns.  What this all has to do with the current discussion is that California Kiln Company designed a custom steam-injection car kiln for Cottet to fire his huge wares.  The wares were often placed in the kiln still damp, and the interior of the kiln was humidified with steam as the temperature was slowly increased.  I have no idea what the heating schedule was, but this allowed those huge forms to dry out fairly quickly without exploding.  I know that a similar process is used in firing large, thick clay forms like sinks and toilets, and maybe someone else on Clayart knows more about this.

The best drying cabinet I have experienced was at the John C. Campbell Folk School.  It was built to accommodate several of their tall ware carts.  Adjustable electric baseboard heaters were installed inside around the base on three sides of the cabinet, and they provided very even convection heat with no fan.  Small vents at the base and the top provided natural convection.  I taught a number of five-day workshops there, always in humid summer weather, a good drying cabinet really helps to maximize production in a five-day workshop.  We dried things quickly in that cabinet, and the only things that broke in the cabinet or subsequently during bisque-firing were a few poorly-joined slab-forms.
- Vince

Vince Pitelka
Potter, Writer, Teacher
Chapel Hill, NC
vpitelka at dtccom.net
www.vincepitelka.com<http://www.vincepitelka.com>
https://chathamartistsguild.org/

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