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grog vs sand in cone 6 clay for tall stuff


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#1 docweathers

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Posted 02 April 2012 - 10:17 PM

I want to get a white cone 6 clay that is good for throwing tall stuff. I understand that it needs to be fortified with sand or grog. I how what these materials are but what difference does it make which the clay contains. My fuzzy understanding it that grog is better and less abrasive on your hands. Is this true and what else is different between the effect of these two additives to add "tooth"? I am concerned that some clay manufacturers use sand instead of grog because it is cheaper. Is this an issue in buying moist clay?

Larry

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#2 Mark C.

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Posted 03 April 2012 - 10:19 AM

All my experience (99%) comes from high fire clays
I think a better mix for throwing large is use both sand and grog
sand is silica which has its own issues with quartz inversion.(Lots of potters use sand in their clay bodies - just keep in mind -
all those grains of quartz will go through the quartz inversion at
573C on the way down during bisque and glaze fire cooling.)



I do know that low fire throwing bodies(used to) not throw as well as high fire bodies
They may have fixed that by now. Cone 6 bodies are in between
Grog will have less issues than lots of sand in my view but some sand will be ok just not to much.
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#3 neilestrick

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Posted 03 April 2012 - 10:32 AM

I think silica sand is much less abrasive, because it is a smoother particle. Grog is very rough, with jagged edges. I like the feel of sand, but others prefer grog. Both work. It's personal preference.
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#4 ThisIsMelissa

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Posted 03 April 2012 - 07:55 PM

On Sunday night, I threw "tall" for the first time.
I threw a carafe... about 11" tall.
I used a cone 6 white clay from Continental Clay. It's their B-Clay.
It was super smooth to throw with.
But I will admit that it took 4 tries to get anywhere close to this height.

#5 Pres

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Posted 04 April 2012 - 06:47 AM

I want to get a white cone 6 clay that is good for throwing tall stuff. I understand that it needs to be fortified with sand or grog. I how what these materials are but what difference does it make which the clay contains. My fuzzy understanding it that grog is better and less abrasive on your hands. Is this true and what else is different between the effect of these two additives to add "tooth"? I am concerned that some clay manufacturers use sand instead of grog because it is cheaper. Is this an issue in buying moist clay?


I guess in the long run it depends on what you call tall? I have thrown cylinders the length of my arm with an off white clay by Standard that has fine grog in it. I found it to be quite smooth and much different to work with than the brown clay that I use, but once you get used to the characteristics quite nice. Some people will call throwing tall 15" others 20" and so forth. Most commercial cone 6 clays are able to go those heights easily, however depending on your throwing style you may find that you have to change your bisque fire to accommodate the taller pots. I had to after having spiral cracks in my pots that went from top to bottom. All of it is a learning process.

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#6 OffCenter

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Posted 04 April 2012 - 09:38 AM

Consider using clay that is as hard as you can center quickly. If too hard you may have to use too much water to center. You don't need grog or sand to throw tall pots. Also, a heat gun helps. If you feel the pot is about to collapse dry it a little, not much, with a heat gun then continue to pull. The bottle below is 19 inches high with very thin walls. It is Laguna's B-Mix Woodfire. It has no grog or sand. The same pot could have been thrown with regular B-Mix which is a white clay for cone 10 or for cone 6.

Jim

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#7 Pres

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Posted 04 April 2012 - 10:54 AM

Consider using clay that is as hard as you can center quickly. If too hard you may have to use too much water to center. You don't need grog or sand to throw tall pots. Also, a heat gun helps. If you feel the pot is about to collapse dry it a little, not much, with a heat gun then continue to pull. The bottle below is 19 inches high with very thin walls. It is Laguna's B-Mix Woodfire. It has no grog or sand. The same pot could have been thrown with regular B-Mix which is a white clay for cone 10 or for cone 6.

Jim


Most of the times while throwing taller cylinders I walk away from the pot for about 30" come back to it, and throw the rest of the cylinder pretty well dry. I use a heat gun on plate rims when laying them out, but prefer to let the pot sit spinning for more even stiffening than the heat gun. Then again too, I am not trying to throw 15 large pots a day, usually limited to 4-5 when doing them.

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#8 docweathers

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Posted 04 April 2012 - 12:17 PM

I like the definitive responses of yes both sand and grog, whatever you like that works for you;), it all depends on whether it's a sunny day or your foot itches:o.

I too use a heat gun and have built a centering device that will let me quickly and easily center 20+ pounds of stiff clay. (I also do welded art, which also allows me to build strange tools for my pottery):rolleyes:

I'm having to ask these strange questions because up until now the University always provided the clay, glazes, kilns and the "night trolls" to put it all together out of my sight and knowledge.

Let me rephrase my original question. Why would a clay manufacture choose to use grog versus sand?

thanks Larry

Larry

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#9 neilestrick

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Posted 04 April 2012 - 12:34 PM

Let me rephrase my original question. Why would a clay manufacture choose to use grog versus sand?

thanks Larry


It all comes down to the preferences of their customers, and the personal preferences of their people formulating the bodies. You'll find that many companies offer some clay bodies that use sand, and some that use grog, and some that use both. That way their customers are sure to find something they like.
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