ISO:potters who make mugs w/ standard 213

[Clay Tile Mom]

I am a production potter. I work with standard 213. I would like to minimize the cracking I am getting where the handles attach.

This is my current process.

I throw the shapes. Let them set up

Pull handles and let them air dry until they are able to be touched.

I scratch and slip. My slip is the same clay body watered down with a couple tablespoons of vinegar.

After handles are attached, I Have been using wax resist at the attachment site, then 8 on a plaster board wrapped with plastic.

I don't touch them for 3-4 days. And I even spritz with water a couple time during the 3-4 days under plastic.

Can anyone think of anything I am not doing???

Thanks

[Pres]

I am a production potter. I work with standard 213. I would like to minimize the cracking I am getting where the handles attach.

This is my current process.

I throw the shapes. Let them set up

Pull handles and let them air dry until they are able to be touched.

I scratch and slip. My slip is the same clay body watered down with a couple tablespoons of vinegar.

After handles are attached, I Have been using wax resist at the attachment site, then 8 on a plaster board wrapped with plastic.

I don't touch them for 3-4 days. And I even spritz with water a couple time during the 3-4 days under plastic.

Can anyone think of anything I am not doing???

Thanks

 

 

I could suggest a few things that might help, but as I have not worked with 213 don't know. Have you tried attaching the handle right after pulling? I do this all of the time as I figure the wet handle will catch up to the cheese to leather hard mug. Another thought here is to wrap the handle area in saran wrap, used to do this but the other way worked better for me. Lastly maybe replace the slip with "magic water"(MW). I hand build and do combination pieces with handbuilding and wheel thrown part. I have found the MW to help with cracking at seams. Just a few thoughts.

[Pompots]

What would be the purpose of spritz the mugs with water while you are trying to dry them? I think if they are very well covered with plastic that should be enough for them to even the moisture on the whole piece, try avoiding this step and see if it makes a difference.

[neilestrick]

First of all, Standard should never have called that clay body a porcelain, even a domestic porcelain. It's not even close to being a porcelain. A domestic porcelain is one that uses domestic kaolin, such as EPK or sapphire instead of grolleg. #213 is a white stoneware at best, but not really even a very good white stoneware. It's really high in ball clay. Too high. I would consider trying #240 if you haven't already. It's formulated much better than the #213, and is much more workable.

 

All that aside, let your handles firm up, in the shape of your desired curve, until they are almost leather hard. Just barely flexible. Then attach. Do not smooth the joint between the cup and handle. If the handle pulls away at all, fill in the crack with slip.

[Paula Patton]

I am a production potter. I work with standard 213. I would like to minimize the cracking I am getting where the handles attach.

This is my current process.

I throw the shapes. Let them set up

Pull handles and let them air dry until they are able to be touched.

I scratch and slip. My slip is the same clay body watered down with a couple tablespoons of vinegar.

After handles are attached, I Have been using wax resist at the attachment site, then 8 on a plaster board wrapped with plastic.

I don't touch them for 3-4 days. And I even spritz with water a couple time during the 3-4 days under plastic.

Can anyone think of anything I am not doing???

Thanks

 

 

Could you explain "I have been using wax resist at the attachment site"????? It's the only red flag I saw, I make a LOT of mugs and haven't had cracking as you describe.

 

 

 

[TJR]

Clay tile mom.

I make a lot of mugs. Last session I made 83.[see my blog about being left at the altar].

!. I agree with Pres. I sponge a ware board, then pull 20 handles all the same length. I then attach these handles. You do not need to let then set up. The slip I use is the residue I scrape off my hand as I pull each handle. I do not use vinegar.

2.I am not familiar with 213 clay, but I have a lot of respect for what Neil says. If there is a lot of ball clay in a clay body, you will get a lot of shrinkage.

3. After I attach handles on a board full of mugs, they will all be resting upside down. I cover the board with plastic over night, tightly, then dry slowly the next day, loosely covered with plastic.

4. The only problems I have, is if the mug body is too dry to accept a handle, then you get a hair line crack.

TJR.

[Mark C.]

I too am a production potter who works in porcelain-I extrude my handles and put them on right then-I do not let them set up. Sometimes I flip the mug so the handle keeps the curve till set then right them.

I score the mug and use slip which is from throwing and the SPLASH PAN (for all you naysayers this is a great use for a pan as this slip has all the goodies in it)-I save all this in a container which I'm always adding to. I do add a splash of vinagar now and then to that as it seems to keep it from getting funky smelling.

Then cover the mugs one night then uncover and let dry. If a small line crack appears I use a sharp wood tool to rub it out. The glaze covers that easy.

Mugs are a staple for me like air is to mammals they flow from the studio like (cash) cows heading to feed.

I know nothing of Standard 213 but if its a stoneware most are very forgiving. I would take Neils advice as he knows that clay.

Mark

[Clay Tile Mom]

First of all, Standard should never have called that clay body a porcelain, even a domestic porcelain. It's not even close to being a porcelain. A domestic porcelain is one that uses domestic kaolin, such as EPK or sapphire instead of grolleg. #213 is a white stoneware at best, but not really even a very good white stoneware. It's really high in ball clay. Too high. I would consider trying #240 if you haven't already. It's formulated much better than the #213, and is much more workable.

 

All that aside, let your handles firm up, in the shape of your desired curve, until they are almost leather hard. Just barely flexible. Then attach. Do not smooth the joint between the cup and handle. If the handle pulls away at all, fill in the crack with slip.

 

Thanks for your input. I am trying to convince the potter that I do production for to change clay bodies. Do you know how the 240 compares to b mix 6? The 213 is temperamental. I think I will go back to no wax, so I can at least fill in cracks with slip.

[Clay Tile Mom]

I am a production potter. I work with standard 213. I would like to minimize the cracking I am getting where the handles attach.

This is my current process.

I throw the shapes. Let them set up

Pull handles and let them air dry until they are able to be touched.

I scratch and slip. My slip is the same clay body watered down with a couple tablespoons of vinegar.

After handles are attached, I Have been using wax resist at the attachment site, then 8 on a plaster board wrapped with plastic.

I don't touch them for 3-4 days. And I even spritz with water a couple time during the 3-4 days under plastic.

Can anyone think of anything I am not doing???

Thanks

 

 

Could you explain "I have been using wax resist at the attachment site"????? It's the only red flag I saw, I make a LOT of mugs and haven't had cracking as you describe.

 

The wax slows down the drying a bit, and has reduced cracking, but on the ones that still crack, I can't go back and fill in because of the wax barrier. Hmmmm

[Clay Tile Mom]

I love all of the comments. Thanks everyone. I will try some new things. I love the upside down drying suggestion. It did dawn on me recently that the weight of the clay may be pulling outward. I will try attaching wet again too, but I find that it is easier for me to pull a bunch then attach. Modifications will be made. I am doing between 30 and 60 in a run right now.