[Clayart] humidity

vincepitelka at gmail.com vincepitelka at gmail.com
Thu Mar 9 17:38:38 UTC 2023

I liked Steven Wright's joke - "I want to put a humidifier and a dehumidifier in a small room and let them fight it out."

When I had Railroad Stoneware in Blue Lake, California form 1975 to 1985, I was doing high production, especially for the last five years before I went off to graduate school.  All my work was wheel-throwin back then.  My studio had a throwing room, a big glazing room, and the kiln room.  Among the items most in demand were slip-trailed or feather-combed plates, platters, bowls, and vases (https://www.vincepitelka.com/gallery/slipware/).  You can't drape them with plastic until after the slip is leather hard.  I had a humidifier and a dehumidifier.  When I was doing a run of slip-decorated pieces, I'd load up a ware cart and roll it into the glazing room, where I'd have the cold-mist humidifier going in the corner.  That would keep all the pieces at approximately the same state of dampness for the several days that I was making a run of plates, platters, bowls, and vases.  Then I'd turn off the humidifier and let the pieces humidify the room as they were stiffening to leather hard.  Once they were trimmed, I'd leave them for a few days, once again letting the evaporating moisture raise the humidity in the room to ensure even drying.  Finally, I'd turn on the dehumidifier to finish drying the pots before bisque-firing.  This worked great, but it did require a room separate from the throwing room.  
- Vince

Vince Pitelka
Potter, Writer, Teacher
Chapel Hill, NC
vpitelka at dtccom.net

-----Original Message-----
From: Clayart <clayart-bounces at lists.clayartworld.com> On Behalf Of Kathy Forer
Sent: Wednesday, March 8, 2023 1:27 PM
To: Clayart <clayart at lists.clayartworld.com>
Subject: Re: [Clayart] humidity

I got turned onto Rodin before we knew much about Camille. I think of his winter struggle with Man with the Broken Nose mask and am ever-grateful for heating, cooling and technology. Before plastic, Auguste and Camille’s labors in wrapping, and before sprays, sculptors would fill their mouths with water to spray out of their teeth. 

Great ideas about swapping out dry cloth to absorb humidity and dry evenly under plastic. 

I’m back to wet linen to keep the surface workable. 

I’ve set up a humidifier. Shouldn’t added humidity have the opposite effect of a dehumidifier? Maybe the machine is only enough to humidify the air and it's not affecting the clay one way or another, just a coincidence. How does clay dry out in the rainforest? 

Kathy Forer

> On Mar 7, 2023, at 11:23 AM, Snail Scott <claywork at flying-snail.com> wrote:
>> On Mar 7, 2023, at 6:48 AM, mel jacobson <melpots at mail.com> wrote:
>> In many ways sheet plastic wrapped around sculptures has the opposite affect.
>> The water migrates to the plastic like a rain forest and drips back 
>> onto the piece….I met an amazing sculptor...She wrapped her sculptures in linen...
> Yes. Plastic is, in my mind, the biggest game-changer in the history of ceramics since the kiln. Gas, electricity, cones, frits…all that is just modifications and upgrades.  Plastic makes keeping clay wet incredibly easy. When Rodin travelled around France, schmoozing the collectors, he left poor Camille Claudel back in the studio to wet down the rags every day,  keeping the work-in-progress workable until he returned. Imagine what she could have accomplished with a box of trash bags and some free time!
> However, plastic is not good for keeping the moisture even, and does not allow clay to dry evenly, either. When sealed up and kept tight to the clay, thick plastic holds moisture in for quite a while. When loosely draped, though, condensation gathers at the top during overnight chill. It drips down onto the top, and runs in rivulets to puddle in the bottom…the bigger the work, the bigger the issue. When people want to start drying the work, they tend to drape the plastic loosely, with gaps which cause uneven evaporation. 
> I cover work in progress with thick cotton sweatshirt fabric or cotton towels under the plastic.  When I want the clay to be softer, I spray the cloth with water, dampening it and creating a humidifier inside the plastic environment. The cloth wicks the moisture evenly, and it catches and redistributes condensation. (For serious rehydration, direct contact with damp cloth is the way to go, though…water is held against the clay and does not run off into a puddle. like sprayed water does.)  When I want the clay to stiffen, I swap the cloth once or twice daily for dry cloth, removing just the moisture that had absorbed from the atmosphere inside the plastic. The cloth does not need contact with the clay to do any of this…it affects the humidity under the plastic, not the clay directly.  The more cloth, the greater the effect, both for dampening and dehydrating. When the entire piece has reached the stiff leather-hard phase, beginning to turn pale, I remove the plastic and wrap it in just cloth. It permits evaporation, but slower and more evenly than open air exposure, with no drafts. I have refined this over many years, and it works. Cloth inside plastic is a portable damp box; and folds flat when not in use! Stacking bins are great for small pots, but not for larger work. 
> It frustrates me to see people covering work well in plastic and wondering why it won’t dry, or draping plastic with big gaps at the side. creating dry spots and irregular shrinkage. Perforated plastic is better, but it can’t move the moisture like cloth can. Drying ’slow’ is not the goal; drying evenly is.
> -Snail Scott

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