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Briana

How long is too long for Greenware

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So I’m a newbie. We purchased a kiln and wheel, but the kiln still isn’t set up. At this point we’re debating moving to another city and purchasing a home there within about a year. To be honest, I’m in no rush to install and set up my kiln where we are now, and I’d rather just save my pennies and set it up at the new house. Which brings me to my question....

How long is too long to let your greenware (I think that’s what it’s called), sit around before firing? I’m under the impression that the danger when firing is in the pot being wet, not too dry. So if I create some things and don’t fire them for say a year (or longer)... what do you think? 

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As long as you keep good notes and know exactly what you knew when you trimmed the pot then time is no limit.  

However know that bone dried greenware is the most fragile state of clay to be moving around. Pack well but be prepared to lose some stuff. 

The other thing is sometimes you create cracks from too much handling that you might not see till after the glaze firing. So watch out for the ping after bisque. If you hear a thud or dull sound then either throw out or use it for glaze test.  

I have know people who have fired after 5 years.  But they hadn’t moved and they had notes.  

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However, understand that “dry” doesn’t necessarily mean leaving a pot just sitting out on a shelf somewhere.  If you live in a climate that cycles through wet and dry seasons, and  cold and hot temperatures extremes, humidity levels in the air can also move up and down substantially over time.   This affects things made out of clay which have not yet been fired.  Dry pots absorb and desorb lots of water from humidity in the air, through the small channels in and around clay particles.  Unfired clay effectively inhales and exhales humidity over time.  Think of it a bit like a rigid sponge.

This matters because clay shrinks and swells as it’s water content changes.  While most of the shrinking happens in the day or two after we take a pot off the wheel, shrinking and swelling stresses are still at work in a small but meaningful way even when we think of the pot as “dry”.  

And different temperatures also promote water movement, in the pot as a whole, and also in different parts of the same pot.

Humidity fluctuations may or may not matter, depending on your clay body and what is in it.  Big, gutsy clay bodies which are relatively “open” ie a good range of large and small particles sizes with grog, silica sand or other aggregate strengtheners, along with sufficient colloidal material may have very good “dry” strength.  Fine porcelain bodies have larger smaller particles, greater surface area, and smaller pore channels, but little in the way of aggregates to strengthen the body, and can be more fragile.   

Different clay body ingredients can also impact how well a clay body withstands humidity cycling.  Sodium Bentonite, for instance, which shrinks and swells dramatically, is a common clay body plasticiser, and small colloidal particles like this are actually the main source of green strength in dry pots.   It is mostly not a a problem since our clay bodies have so little of it, but should not be forgotten, as some bodies lean on bentonite more heavily.   Ball clay shrinks and swells less than bentonite, but there is usually a lot more of it than bentonite in clay bodies we use.

Point of all of this is that pots can be negatively impacted by humidity cycling, and to a lesser extent temperature cycling, causing weakness, cracks which show up later during glaze firing, and in extreme circumstances even dry pots disintegrating where they sit.   The longer you leave them exposed, the greater the risk.  

The extreme version of all this would be if your studio is in a rainforest, and you leave a pot on top of the kiln you fire every couple of weeks, and which is also exposed to the sun on one side.   That should be the perfect storm. 

Moral of the story is if you want your dry pots to last and fire OK later,  try to avoid putting them through conditions like this.

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If you're moving, I'd strongly suggest at least bisquing the pots in a friend's kiln before you do. Greenware does NOT travel well, no matter how you pack it.  

I used to transport all my work to an arts centre to fire.  There were 47 manhole covers in between my house and the arts centre.  I had to make about 20% more work than I needed because of those suckers. 

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Thanks for all the information. I hadn’t considered the fragility when it comes time to moving, so thank you for that!! As well as the bits on humidity cycling, also helpful. 

I’ll have to come up with some sort of system, or perhaps fire them in another kiln. I’m learning something new everyday and I’m grateful this forum exists!!

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On 5/21/2018 at 3:03 PM, hantremmer said:

After I trim a pot I inscribe the date on the bottom.

Not just the date, the clay type/firing temp is essential when you're not going to fire for a while. 

Edited by Rae Reich

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Briana you are a newbie you said.  

I’d say forget about keeping.  Forget about firing.  Just keep throwing.  And trimming and then slicing in half to check for area of improvement. It’s been 2 1/2 years since I first touched the wheel.  I have kept none of the murder weapons from my first year.  I’ve always kept one piece from each semester to see how good I’ve gotten, but otherwise I’ve given away (mostly) sold (a few) almost all my pots.  I do bring them home to use to see what I like. So at the end of my semester I do a drastic cut of what I had at home from the previous semester.  

In the meantime try to find a studio or potter who will bisque for you. 

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9 minutes ago, preeta said:

Briana you are a newbie you said.  

I’d say forget about keeping.  Forget about firing.  Just keep throwing.  And trimming and then slicing in half to check for area of improvement. It’s been 2 1/2 years since I first touched the wheel.  I have kept none of the murder weapons from my first year.  I’ve always kept one piece from each semester to see how good I’ve gotten, but otherwise I’ve given away (mostly) sold (a few) almost all my pots.  I do bring them home to use to see what I like. So at the end of my semester I do a drastic cut of what I had at home from the previous semester.  

In the meantime try to find a studio or potter who will bisque for you. 

You know I’ve heard this from a vew tutorial videos!! That might not be a bad idea. It would certainly eliminate the issue with fragility and keeping one will allow me to track my progress!!! I like it.

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On 5/23/2018 at 7:42 PM, Rae Reich said:

Not just the date, the clay type/firing temp is essential when you're not going to fire for a while. 

Good point.  I have been writing the clay name if it's one I don't normally use, but doing it consistently would be a better idea.    A lot of my foot rings are quite small, so there isn't much space.  I might be able to use the trimming date and then a number for each pot trimmed on that date.  That way I could keep a log in my notebook.

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19 hours ago, hantremmer said:

Good point.  I have been writing the clay name if it's one I don't normally use, but doing it consistently would be a better idea.    A lot of my foot rings are quite small, so there isn't much space.  I might be able to use the trimming date and then a number for each pot trimmed on that date.  That way I could keep a log in my notebook.

You can establish a code number/letter that would be easier to inscribe on small areas, just don't lose the code! ;)

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