Ababi on mon 26 may 03
I wonder John,
I will test it of course
If I will paperclay out of Laguna's English Porcelain. In my test it had 0.2% absorption.
If I will arrive to 2-3% absorption will it be fine?
Ababi
---------- Original Message ----------
>Hi Cindi,
>I suppose porosity and absorption could be different, but, from a
>potter's viewpoint, I'm not sure it makes practical sense to try to
>differentiate between them. Absorption is the amount of water a fired
>clay will "take up". To measure it you usually start with a test bar
>fresh out of the kiln that you know is dry. You weigh it. Then you
>treat it so it will absorb as much water as it can. This is usually
>done by boiling it under water for a couple hours and letting it cool
>while still under water. Then you quickly dry off the surface water and
>weigh it again. The difference is the amount of water it absorbed.
>Whether or not a fired clay leaks will depend on whether or not the
>clay is vitrified which will also be pretty directly related to how
>much water it absorbs. The higher the absorption the more likely it is
>to leak. I suppose there could be a structure that was fully vitrified
>but had tiny continuous channels all the way through it so it would
>leak but have fairly low absorption--maybe that is what this person was
>visualizing.
>To give you some numbers, well vitrified stoneware clays have
>absorptions of 2-3% or less and they don't leak. Porcelain is usually
>1% or less and it doesn't leak. Earthenware has an absorption of 10-15%
>and it normally leaks. I haven't personally seen low absorption fired
>clay bodies that leak, but maybe Laguna has some--you'd have to ask
>them.
>Regards,
>John
John Hesselberth on mon 26 may 03
On Monday, May 26, 2003, at 12:13 AM, Ababi wrote:
> If I will arrive to 2-3% absorption will it be fine?
Hi Ababi,
That has been my experience, but always test, test, test. If you want
a severe test for leaking put a light weight oil like lamp oil or
kerosene in an unglazed pot. Set it on some blotter paper and check
back in a week or two. Make sure you do this in a way you don't create
a fire hazard. Low molecular weight hydrocarbons are extra hard to keep
in a pot--that is why so many potters make/sell oil lamps that leak and
later wish they hadn't. They, of course, don't realize they leaked--it
takes a while for the oil to seep through.
Regards,
John
http://www.frogpondpottery.com
http://www.masteringglazes.com
Ababi on tue 27 may 03
Thank you John
By the way is there any different as the final point between porosity and absorption
or the way it is in your book between stable and durable?
If one is wrong can the other be right?
By the way:
>That has been my experience, but always test, test, test.
More than you believe
Ababi
---------- Original Message ----------
>On Monday, May 26, 2003, at 12:13 AM, Ababi wrote:
>> If I will arrive to 2-3% absorption will it be fine?
>Hi Ababi,
>That has been my experience, but always test, test, test. If you want
>a severe test for leaking put a light weight oil like lamp oil or
>kerosene in an unglazed pot. Set it on some blotter paper and check
>back in a week or two. Make sure you do this in a way you don't create
>a fire hazard. Low molecular weight hydrocarbons are extra hard to keep
>in a pot--that is why so many potters make/sell oil lamps that leak and
>later wish they hadn't. They, of course, don't realize they leaked--it
>takes a while for the oil to seep through.
>Regards,
>John
>http://www.frogpondpottery.com
>http://www.masteringglazes.com
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Ababi on wed 28 may 03
Thank you John
The kerosine test will wait to the winter it is hot enough I would not leave an open mug
where children are wondering around . I will run some other tests and let you know.
Ababi
---------- Original Message ----------
>On Monday, May 26, 2003, at 12:13 AM, Ababi wrote:
>> If I will arrive to 2-3% absorption will it be fine?
>Hi Ababi,
>That has been my experience, but always test, test, test. If you want
>a severe test for leaking put a light weight oil like lamp oil or
>kerosene in an unglazed pot. Set it on some blotter paper and check
>back in a week or two. Make sure you do this in a way you don't create
>a fire hazard. Low molecular weight hydrocarbons are extra hard to keep
>in a pot--that is why so many potters make/sell oil lamps that leak and
>later wish they hadn't. They, of course, don't realize they leaked--it
>takes a while for the oil to seep through.
>Regards,
>John
>http://www.frogpondpottery.com
>http://www.masteringglazes.com
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