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Warped Base On My Paper Clay Vases

paperclay warping

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#1 Lizzy

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Posted 20 May 2014 - 08:14 AM

Hallo!

I am having a problem with warping bases in my paper clay vases.

I use paper clay slabs to build my vases. I dry my vases slowly, covering the body and the top of the vase with a plastic bag. After a few days of drying, I find that the foot has warped and my vase wobbles. Someone suggested that I place the vase on a piece of plaster so that the moisture can be absorbed from the foot, which tends to dry slower than the rest. This didn´t help - it warps either way!

I can often save my vase by sandpapering the base carefully, (yes, I know, the dust) however when I do the bisque firing, the base warps again! I fire to 960° C (100°C per hour). 

Does anyone have suggestions? I really don´t know what else to try out....

Regards, Lizzy

 



#2 Benzine

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Posted 20 May 2014 - 08:55 AM

Sounds like an issue with clay memory. Are they slab built? If so, are you flipping and/ or rotating the slabs, when you roll them out?
"Anything worth believing, is worth questioning"

#3 Marcia Selsor

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Posted 20 May 2014 - 10:55 AM

Do they have a foot or a flat base? You could try putting an actual ridged foot on the bottom or build legs.
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#4 Lizzy

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Posted 20 May 2014 - 11:08 AM

Hi!

I do rotate while rolling out, but perhaps I need to rotate more. Will try....

The base is always flat, no foot ring. The foot is quite small for the vase so I´m not sure a foot ring would be a good idea.

I have built these vases before ands never had a problem. That´s what irritates me - I just can´t explain it. The clay is the  same, method of working is the same....

Thanks for your suggestions :-))



#5 Lizzy

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Posted 20 May 2014 - 11:17 AM

I would like to post a photo on this page. is it possible?



#6 neilestrick

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Posted 20 May 2014 - 11:36 AM

It's most likely because of the flat foot. You don't have to make a foot ring, but push in the center of the foot so that it rests on the outer edge only.


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#7 Lizzy

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Posted 20 May 2014 - 01:07 PM

Good idea. Hadn't thought of that one .Will definitely try. Thank you :-)

#8 Lizzy

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Posted 21 May 2014 - 08:33 AM

https://plus.google....140884627662888

 

This is a google link to a photo of my vase. Somehow I can´t get my photos small enough for attachment, sorry.

The foot is an oval with sharp ends. It´s the short sides that roll up like a leaf....about 1 mm on each side. Just enough to make it wobble....



#9 CATHFITZ

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Posted 21 May 2014 - 09:47 AM

Cannot get your photograph up - just a black sceen!



#10 Lizzy

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Posted 21 May 2014 - 10:20 AM

Sorry!

 

Second try:

https://plus.google....CMrP6ozPq9K1tgE



#11 CATHFITZ

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Posted 21 May 2014 - 01:10 PM

Photo work this time.  Lovely pot.   The suggestion of pushing up centre of foot sounds like a good one.  

Otherwise, maybe if the base was a little bit thicker it would not be so inclined to curl.   Good luck!



#12 Lizzy

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Posted 22 May 2014 - 02:41 AM

Thank you :-) I will definitely give it a try.



#13 Karen B

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Posted 22 May 2014 - 08:20 AM

I hope you don't mind this explanation of Neil's suggestion. When the pot dries and shrinks, the bottom gets squeezed around it's edge. This is bowing it so it wobbles.. If you use the heel of your hand to tap it so it is concave, any bowing will go inward and not affect the balance. 

It is a beautiful piece.



#14 Benzine

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Posted 22 May 2014 - 08:30 AM

Karen, I don't mind the explanation. I always like to know the "Why" of things. Great information.
"Anything worth believing, is worth questioning"

#15 Lizzy

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Posted 23 May 2014 - 12:15 AM

Than you for the advice!





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