Drying tips please

[shawnhar]

Another hard lesson to learn, biggest pot to date, 16lbs planter over 12" tall, cracked, right down the whole thing, top to bottom.

 I have since been informed you have to dry them upside down, and slower. I have one remaining large planter, and the rim is already drying faster than the base. It is currently inside a large plastic bag, rim down. 

What suggestions would you give for drying a large pot like this in a shared studio? I have a shelf maybe 15"x 36" and no where else to store items. It seems wrapping them in plastic almost stops the drying process. I am only there a couple of days per week, should I be unwrapping the "wettest" portion while I am there so it catches up to the drier rim, or leave the entire item enclosed in a bag or wrapping in a cloth or something?  Not sure how "air tight" or what the best wrapping techniques are for even drying.

[dhPotter]

You can do partial drying. Tear strips of plastic about 3-5 inches wide. Spritz a strip of plastic with water then wrap the rim only, or whatever part is drying faster than the rest of the piece. 

You are going to have to figure out the drying in that studio. it may take a few lost pieces to get this part of pottery production under control. 

Always something new to learn... 

[Rae Reich]

1 hour ago, dhPotter said:

 

You can do partial drying. Tear strips of plastic about 3-5 inches wide. Spritz a strip of plastic with water then wrap the rim only, or whatever part is drying faster than the rest of the piece. 

 

If you do this, or even put a bag over only the upper 2/3s,  don't flip the pot right away, as the rim could get mushy when the moisture descends. Set the pot on two or three sticks so the base can get air circulation. 

[Gabby]

Shawnhar, are you using the most practical clay for large planters that you cannot oversee closely throughout the drying process?

I ask this because some clays are so much fussier than others about cracking in drying.

I use some porcelain that on larger items cracks as soon as my back is turned (well, not really, but I had a very satisfying large bowl crack even after serious coddling) My red clay doesn't crack for a pot 8" high and 8" wide drying in the basement in my never dry climate, even without any period of being covered in plastic.  And then there is the really groggy clay that my clay supply place recommended for large hand-built work.  Since my clay place mixes their own, the names of any wouldn't be useful.

None of this helps that last pot, but it might be worth a thought for the future.

 

[Min]

Another thing you can try is to wax the rim and top few inches of the pots with wax resist to slow the drying down there plus cover the upper part of the pot with plastic. Unless the rim is quite dry when you flip it over a large pot can drag on the shelf and get pulled out of round as it shrinks.  Once the lower part of the pot has caught up with the top of the pot you can remove the plastic and cover with a piece of fabric (old cotton bedsheets work well) to keep drafts off. You can dry pieces quickly but it's the evenness of the drying that is important.

[Mark C.]

For me the best way to even drying  working with stoneware (which I assume you are as you are saying what clay this was)

When the rim is just dry enough to put a bat on the top you flip the pot. It should be cut off the bottom bat right after throwing it.

Then pop the bottom bat off and you can wrap the top (now upside down) with plastic and let the bottom catch up with the top.

Working with a courser clay for large forms will help all this as well.

[neilestrick]

You can dry a pot of that size without cracking if it's constructed well. Make sure it's thrown and trimmed evenly. Variations in thickness from top to bottom can cause a lot of problems in pots of that size. If it's really thin at the top and thick at the bottom you'll definitely have problems. Ease off on your pulls as you get toward the top, so the top half doesn't get too thin. Trim it well and get all the excess clay out of the bottom. And also, as you noted, dry it upside down.

[shawnhar]

Thanks for the feedback!

 My class started Monday so I'm happy about that, hopefully avoid some of these newb mistakes and get active feedback on what I'm doing. I'm realizing there is so much I've forgotten since high school.

I have 2 remaining large pots and I think they may survive. I've evened out the drying on the 1st one so the rim is about the same as the bottom and it is currently sitting under newspaper since Monday with the hopes that it will be ready for bisque tomorrow, it's been drying for like 2 weeks now.

will use the info you guys provided to carefully dry the other.  Also moved to a clay with some grog in it (oww!) Gabby, I def used the wrong clay, Bmix-5 with no grog, almost porcelain and apparently very finicky about drying.

 

[neilestrick]

White stoneware clays like B-Mix and others are more finicky than porcelain. They have very fine particles, and poor particle size distribution. Any stoneware with fireclay or grog will work better.