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Bubbles in pugged clay


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#1 Claypple

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Posted 07 June 2013 - 11:30 PM

I use Laguna clay that comes in 25# bags. It is already pugged.
I cut it with a wire and it seems to be homogenous. I do not think I need to wedge it.
However, when I through it on the wheel, I often feel bubbles of air and pockets. Since I through thin, they usually disappear as I lift the vessel,
so I have not had any pots/bowels explode in the kiln yet. Does what I described happen very often? Do I have to wedge pugged clay?

#2 Pres

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Posted 08 June 2013 - 12:01 AM

I use Laguna clay that comes in 25# bags. It is already pugged.
I cut it with a wire and it seems to be homogenous. I do not think I need to wedge it.
However, when I through it on the wheel, I often feel bubbles of air and pockets. Since I through thin, they usually disappear as I lift the vessel,
so I have not had any pots/bowels explode in the kiln yet. Does what I described happen very often? Do I have to wedge pugged clay?


Could be a bad batch. The air bubbles in the clay are a nuisance, but in the long run, I think it is a fallacy that bone dry pottery will explode if there is a small bubble in the wall of the pot. I know that I have had some air bubbles, never a problem, unless of course the pot is not dried completely and the area around the pocket is damper than the rest.

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#3 Claypple

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Posted 08 June 2013 - 12:59 AM

I think it is a fallacy that bone dry pottery will explode if there is a small bubble in the wall of the pot. I know that I have had some air bubbles, never a problem, unless of course the pot is not dried completely and the area around the pocket is damper than the rest.


Oh, I feel better now! Thank you.

#4 Mart

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Posted 08 June 2013 - 03:55 AM


I use Laguna clay that comes in 25# bags. It is already pugged.
I cut it with a wire and it seems to be homogenous. I do not think I need to wedge it.
However, when I through it on the wheel, I often feel bubbles of air and pockets. Since I through thin, they usually disappear as I lift the vessel,
so I have not had any pots/bowels explode in the kiln yet. Does what I described happen very often? Do I have to wedge pugged clay?


Could be a bad batch. The air bubbles in the clay are a nuisance, but in the long run, I think it is a fallacy that bone dry pottery will explode if there is a small bubble in the wall of the pot. I know that I have had some air bubbles, never a problem, unless of course the pot is not dried completely and the area around the pocket is damper than the rest.


If water (H2O) molecules can get out, so can "air" or more precisely mixture of gases like Nitrogen (N2, ~78.1%) Oxygen (O2, ~20.9%) Argon (Ar, ~0.93%) Carbon dioxide (CO2 ~0.04%) etc

Btw, I had my first exploding pots and this happened in bisque firing. I have no idea why it happened. I had 10 identical pots, same claybody, same thickness etc. Some of the pots needed more drying so programmed the kiln to sit at at 82C for 4 h and then start the normal bisque firing schedule. I am 70% sure that the ones exploded are the ones needed more drying.

I guess I have to state the obvious "hurrying and cutting corners is total waste of time" :)

#5 OffCenter

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Posted 08 June 2013 - 07:53 AM

I use Laguna clay that comes in 25# bags. It is already pugged.
I cut it with a wire and it seems to be homogenous. I do not think I need to wedge it.
However, when I through it on the wheel, I often feel bubbles of air and pockets. Since I through thin, they usually disappear as I lift the vessel,
so I have not had any pots/bowels explode in the kiln yet. Does what I described happen very often? Do I have to wedge pugged clay?


Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

BIG FALLACIES THAT WILL NOT GO AWAY: (1) AIR BUBBLES CAUSE CLAY TO EXPLODE. (2) CLAY FIRED TO HIGHER CONES IS STRONGER THAN CLAY FIRED TO LOWER CONES.

Jim
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#6 minspargal

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Posted 08 June 2013 - 07:56 AM

I too have fired things with small bubbles and they were fine.

#7 Benzine

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Posted 08 June 2013 - 10:18 AM


I use Laguna clay that comes in 25# bags. It is already pugged.
I cut it with a wire and it seems to be homogenous. I do not think I need to wedge it.
However, when I through it on the wheel, I often feel bubbles of air and pockets. Since I through thin, they usually disappear as I lift the vessel,
so I have not had any pots/bowels explode in the kiln yet. Does what I described happen very often? Do I have to wedge pugged clay?


Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

BIG FALLACIES THAT WILL NOT GO AWAY: (1) AIR BUBBLES CAUSE CLAY TO EXPLODE. (2) CLAY FIRED TO HIGHER CONES IS STRONGER THAN CLAY FIRED TO LOWER CONES.

Jim


I will admit, that I propagate the air bubble one to my students. I find it easier, to make them fear, any air pocket, than to have them skip wedging, because "It won't be a big deal".

Also, someone gave you a positive rating on your post. Madness!
"Anything worth believing, is worth questioning"

#8 Mark C.

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Posted 08 June 2013 - 11:39 AM

You do not have to wedge clay before throwing it.Wedging does line up the particiles and it works better.Laguna clay can have small bubbles rocks and wood in it(I have a small pile of this stuff by my wheel) I've also seen it with a few tubes of silicone chunks per ton. That said since I had some wrist bones removed in early 2012 I have done far less wedging with almost no effects on thrown wares.
When you are working larger amounts of clay spiral wedging will help. Cut and slap will remove some of issues.The best way to learn this all is to try these different techniques and see what works for you.
Mark
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#9 OffCenter

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Posted 08 June 2013 - 11:42 AM



I use Laguna clay that comes in 25# bags. It is already pugged.
I cut it with a wire and it seems to be homogenous. I do not think I need to wedge it.
However, when I through it on the wheel, I often feel bubbles of air and pockets. Since I through thin, they usually disappear as I lift the vessel,
so I have not had any pots/bowels explode in the kiln yet. Does what I described happen very often? Do I have to wedge pugged clay?


Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

BIG FALLACIES THAT WILL NOT GO AWAY: (1) AIR BUBBLES CAUSE CLAY TO EXPLODE. (2) CLAY FIRED TO HIGHER CONES IS STRONGER THAN CLAY FIRED TO LOWER CONES.

Jim


Also, someone gave you a positive rating on your post. Madness!


Holy Crap! I can't believe it!
E pur si muove.

"But it does move," said Galileo under his breath.

#10 Biglou13

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Posted 08 June 2013 - 12:44 PM

I'm old school so

+1 for wedging!!!

Isn't cut and slap a form of wedging (semantics )

Even if I don't need to I'm still wedging..... The clay needs to know who is boss!!!!!

Jim... I was hoping to see what rating is beyond negative 20...... :) lol
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#11 Claypple

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Posted 09 June 2013 - 12:13 AM

Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

Jim


Thank you very much! Will do.
Yet, 1) Why are we still talking about getting the air out, since it is not a big deal?
2) Why are we chatting (in other threads) about buying a pug mill, if we still need to wedge?

JUST CURIOUS Claypple.

#12 clay lover

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Posted 09 June 2013 - 06:28 AM


Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

Jim


Thank you very much! Will do.
Yet, 1) Why are we still talking about getting the air out, since it is not a big deal?
2) Why are we chatting (in other threads) about buying a pug mill, if we still need to wedge?

JUST CURIOUS Claypple.


For me, the air bubble, if of any size, will be a flaw in the wall of the finished pot . It's more about that than about fear of exploding.

The clay in a bag is not like the clay fresh from a de-airing pug mill. Open a bag of clay, cut off a fat slice of it and look at the edges. There will often be a ring around the edge, maybe 1" wide, that is a lighter color. That means it is a different moisture level. You wedge that clay to get the moisture even through out the ball of clay you want to throw. Or cut and slap.

Fresh pugged clay is not that way, although if it sits for a while it can become that way. The moisture migrates through the clay , even when it is wrapped. I don't prep more balls of clay that I will throw in one day because of that. If I don't get to all I have ready, I toss it back in the pugger.

I will wedge just a few rounds to change the spiral from the pugging so as to not have S cracks. OR make sure I don't sit the ball on the wheel with the cut end of the pug against the wheel, if that makes sense. Or to get the mass in the shape I want it to go on the wheel. MUCH less wedging that before pug mill.

#13 OffCenter

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Posted 09 June 2013 - 08:38 AM


Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

Jim


Thank you very much! Will do.
Yet, 1) Why are we still talking about getting the air out, since it is not a big deal?
2) Why are we chatting (in other threads) about buying a pug mill, if we still need to wedge?

JUST CURIOUS Claypple.


1) It is a big deal. Air pockets, depending on size, interfere with throwing and show up as a lump in the wall of a fired pot. I make a big deal out air pockets not causing pots to explode because that myth is still so prevalent. No, they don't make pots explode but you do not want them in the clay you are throwing (unless you do want them there for an aesthetic reason).
2) My pugmill (Peter Pugger) ruins clay, but I'm the exception. For most people pugmills are these wonderful machines that take most of the work out of reclaiming clay and produces clay that needs almost no wedging.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#14 Pres

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Posted 09 June 2013 - 09:38 AM

Claypole, for me it is a matter of exercise, and movement with the clay out the bag when I wedge it. I spiral wedge all of the clay I use over 300 turns. I like to wedge, sometimes for a couple of hours at a time. Air bubbles in the clay are a real pain when trying to throw tall, or thin, or for a tight thrower like I am, so I wedge, and if still have an air bubble I puncture and keep on throwing. I am still able to wedge up to 25# at a time IF I want to. I let my clay freeze in the winter as I am storing it outside under tarp. These means that my clay has lots of irregular areas in it from freezing and thawing. Wedging returns it to normal for me, and dries it a bit. When I throw I like the clay to be stiffer for all but plates. I only use about a ton a year, so in the end I really don't need a pug mill. Now the exceptions here would be if I get so old or frail that I cannot wedge. Instead of stopping to throw and make pots, I would buy a pug mill. Unthinkable not to make pots.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#15 justanassembler

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Posted 09 June 2013 - 09:42 AM



Wedge it!. The clay in the bag needs to be wedged. The cut and slap is better at getting air out but spiral shell wedging works the clay nicely, lines up particles, and lets the clay introduce itself to you, so do a little of both.

Jim


Thank you very much! Will do.
Yet, 1) Why are we still talking about getting the air out, since it is not a big deal?
2) Why are we chatting (in other threads) about buying a pug mill, if we still need to wedge?

JUST CURIOUS Claypple.


1) It is a big deal. Air pockets, depending on size, interfere with throwing and show up as a lump in the wall of a fired pot. I make a big deal out air pockets not causing pots to explode because that myth is still so prevalent. No, they don't make pots explode but you do not want them in the clay you are throwing (unless you do want them there for an aesthetic reason).
2) My pugmill (Peter Pugger) ruins clay, but I'm the exception. For most people pugmills are these wonderful machines that take most of the work out of reclaiming clay and produces clay that needs almost no wedging.

Jim


What Jim said is absolutely true--additionally, one of the reasons that people buy clay is to avoid having to process it themselves--you are paying to save time and effort, you are paying to have de-aired, pugged clay. If you're not getting that, it really behooves you to let the distributor/manufacturer know, and it helps them maintain quality standards as well.

#16 Claypple

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Posted 09 June 2013 - 09:48 AM

if I get so old or frail that I cannot wedge. Instead of stopping to throw and make pots, I would buy a pug mill.


You will always be able to wedge by "cut and slam" technique. Wouldn't you?

Thank you all!

#17 Pres

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Posted 09 June 2013 - 10:17 PM

[
You will always be able to wedge by "cut and slam" technique. Wouldn't you?


Hoping I don't get that poorly, and do all I can to keep from it.Posted Image

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#18 Mark C.

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Posted 10 June 2013 - 04:06 AM

[
You will always be able to wedge by "cut and slam" technique. Wouldn't you?


Hoping I don't get that poorly, and do all I can to keep from it.Posted Image


(if I get so old or frail that I cannot wedge)
More like we cannot find the studio I think
mark
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