Lee Love on sun 27 jul 08
I heard an interesting interview with the author of __The Science Of
Fear__. It relates to our discussion about crazing.
You can read about the book here:
http://www.mcclelland.com/catalog/display.pperl?isbn=9780771032998
"We are the safest and healthiest human beings who ever lived, and yet
irrational fear is growing, with deadly consequences "
--
Lee Love in Minneapolis
http://mashikopots.blogspot.com/
http://claycraft.blogspot.com/
"Let the beauty we love be what we do.
There are hundreds of ways to kneel and kiss the ground." --Rumi
Michael Wendt on sun 27 jul 08
I set up a spreadsheet with 15 digit display to
calculate the actual space that exists between
the faces of the glaze discontinuities.
I chose as a thermal expansion 6.0 x 10^-6
I chose a temperature range of 280 degrees
Celsius because in my experience crazing
sounds do not occur until about that temperature
if you open the kiln and let it crash cool.
It turns out the gap is around 0.0000016 m.
I Googled bacterial dimensions and found the
average given is about 0.0000015 m on the narrow
axis for rod form bacteria. That leaves virtually
no room for growth, reproduction, circulation
of surrounding water to carry away wastes.
You get the picture. Craze lines are huge gaps
in the glaze when compared to water, oils, some
organic stains, but right on the boundary of
tight for average bacteria on the narrow axis
and way narrower than bacteria on the long
axis.
Concern for viruses is probably even lower
since they lack the motility of bacteria which
can move about either by pseudopodia or
flagella.
We have the tools at our disposal to figure
stuff like this out. Please, someone else run the
numbers and see if I am wrong.
Bottom line, bacteria may be able to fit
into the craze lines but it will be snug.
Larger species would not fit at all.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
Eva Gallagher on sun 27 jul 08
Love your post and thanks for doing the calculation! I was thinking along
the same lines but just did not have any idea where to start and do the
calculation.
Eva Gallagher
Deep River ,Ontario
----- Original Message -----
From: "Michael Wendt"
To:
Sent: Sunday, July 27, 2008 3:41 PM
Subject: Re: Crazing Hazards.. Let's do the math
>I set up a spreadsheet with 15 digit display to
> calculate the actual space that exists between
> the faces of the glaze discontinuities.
> I chose as a thermal expansion 6.0 x 10^-6
> I chose a temperature range of 280 degrees
> Celsius because in my experience crazing
> sounds do not occur until about that temperature
> if you open the kiln and let it crash cool.
> It turns out the gap is around 0.0000016 m.
> I Googled bacterial dimensions and found the
> average given is about 0.0000015 m on the narrow
> axis for rod form bacteria. That leaves virtually
> no room for growth, reproduction, circulation
> of surrounding water to carry away wastes.
> You get the picture. Craze lines are huge gaps
> in the glaze when compared to water, oils, some
> organic stains, but right on the boundary of
> tight for average bacteria on the narrow axis
> and way narrower than bacteria on the long
> axis.
> Concern for viruses is probably even lower
> since they lack the motility of bacteria which
> can move about either by pseudopodia or
> flagella.
> We have the tools at our disposal to figure
> stuff like this out. Please, someone else run the
> numbers and see if I am wrong.
> Bottom line, bacteria may be able to fit
> into the craze lines but it will be snug.
> Larger species would not fit at all.
> Regards,
> Michael Wendt
> Wendt Pottery
> 2729 Clearwater Ave.
> Lewiston, Id 83501
> U.S.A.
> 208-746-3724
> wendtpot@lewiston.com
> http://www.wendtpottery.com
> http://UniquePorcelainDesigns.com
>
>
Taylor Hendrix on sun 27 jul 08
Hey Smarty Pants:
So your theoretical model assumes what type of shape between faces?
Are these faces parallel or do they converge at some point below the
glaze's outer surface. Does glaze thickness determine how wide a craze
line will open? Do craze lines open and close any during the normal
use of functional ware?
Thanks for the grounded evaluation. I'm diggin' it.
Boy, I sure wish some other smarty pants like Dave F. would borrow an
electron microscope or something and do some actual measurements of
glaze fractures. Where's a ceramic technologist when you need one?
Taylor, in Rockport TX, where he has to pour concrete in preparation
for framing in the garage. It's going to hurt...
On Sun, Jul 27, 2008 at 2:41 PM, Michael Wendt wrote:
> I set up a spreadsheet with 15 digit display to
> calculate the actual space that exists between
> the faces of the glaze discontinuities.
> I chose as a thermal expansion 6.0 x 10^-6
> I chose a temperature range of 280 degrees
> Celsius because in my experience crazing
> sounds do not occur until about that temperature
> if you open the kiln and let it crash cool.
> It turns out the gap is around 0.0000016 m.
> I Googled bacterial dimensions and found the
> average given is about 0.0000015 m on the narrow
> axis for rod form bacteria.
...
Leigh Whitaker on sun 27 jul 08
In a message dated 7/27/2008 5:39:18 P.M. Eastern Daylight Time,
wendtpot@LEWISTON.COM writes:
It turns out the gap is around 0.0000016 m. I Googled bacterial dimensions
and found the
average given is about 0.0000015 m on the narrow
axis for rod form bacteria.
I don't really have an opinion on the crazing issue. I like my stuff not to
craze for aesthetic reasons, but dishwasher temperatures kill most bacteria
and we do have immune systems that are made for this sort of thing). So I
guess you could put me in the camp that strives to avoid crazing, but I don't
see much potential for illness caused by it.
I did want to point out a potential snag in your argument though. You are
using the average size of bacteria. Some bacteria are quite large (up to 2 um
in diameter or 2 x 10 E-6 m). While some like mycoplasma are quite small
(0.2um diameter or 2 x 10 E-7 m).
You calculated the gap to be 0.0000016 m (or 1.6 x 10E-6 m). There is
about an order of magnitude difference between that and the smallest diameter for
bacteria (that leaves room for ~8 bacteria of Mycoplasma size to span a gap
of 1.6 x 10E-6 m). I'd also be hesitant to accept the size of the gap based
on calculations only as well. It would be very interesting if someone
actually measured craze gaps (which could be done on a nice microscope w/camera and
measuring functions). If I still worked in a lab I would attempt it, but I
don't. I would imagine that actual gap sizes could vary widely depending on
a lot of not very well defined variables.
Leigh Whitaker
visit my etsy shop at _http://www.leighwhitaker.etsy.com_
(http://www.leighwhitaker.etsy.com/)
visit my blog at _http://leighwhitaker.blogspot.com/_
(http://leighwhitaker.blogspot.com/)
That leaves virtually
no room for growth, reproduction, circulation
of surrounding water to carry away wastes.
You get the picture. Craze lines are huge gaps
in the glaze when compared to water, oils, some
organic stains, but right on the boundary of
tight for average bacteria on the narrow axis
and way narrower than bacteria on the long
axis.
Concern for viruses is probably even lower
since they lack the motility of bacteria which
can move about either by pseudopodia or
flagella.
We have the tools at our disposal to figure
stuff like this out. Please, someone else run the
numbers and see if I am wrong.
Bottom line, bacteria may be able to fit
into the craze lines but it will be snug.
Larger species would not fit at all.
(http://leighwhitaker.blogspot.com/)
**************Get fantasy football with free live scoring. Sign up for
FanHouse Fantasy Football today.
(http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)
Ivor and Olive Lewis on mon 28 jul 08
Did I mention "Dye Disclosure" a couple of issues ago?
That was in terms of exposing fractures in a glaze surface.
But the rap today reminded me that Dental Surgeons have dye
disclosure markers that reveal bacterial deposits on teeth. I think
they use Eosin, a bright red dye. Test crazed pottery with a this.
I'm sure a DS would donate a tablet in the aid of discovery.
Another point. With unaided vision the lower limit of discrimination
for an adult with 20/20 vision is about one tenth of a millimetre at
reading distance. . Most of black dyed pottery I have seen shows
prominent cracks, easily visible to the unaided eye. !/10 mm is about
100 microns. With a X 10 hand lens your would be able to view
something 10 mu. Michael Wendt gave a near estimate differing by only
an order of magnitude.
There seem to be some wonderful chances for a little practical
investigation.
Sorry, I have no specimens to test. I don't use glaze/clay
combinations that are incompatible.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ric Swenson on mon 28 jul 08
I have to 'choose' to get a crazing glaze. None of my glazes craze....or crackle as a matter of normal use......
I sometimes 'choose' to have a crackled glaze.....but I have to test it to make sure it will perform that waY. FOR AESTHETIC PURPOSES.....NOT FOR FOOD WARES.... My wares made for food consumption never craze. It is an effect ..rather than for aesthetic reasons. It is beautiful on vases and sculptural forms....not needed or wanted.......... on food service wares.
Crazing is easy to control with careful attention to RO formula.
Bacteria be damned.
IMHO
Ric
"...then fiery expedition be my wing, ..." -Wm. Shakespeare, RICHARD III, Act IV Scene III Richard H. ("Ric") Swenson, Teacher, Office of International Cooperation and Exchange of Jingdezhen Ceramic Institute, TaoYang Road, Eastern Suburb, Jingdezhen City.JiangXi Province, P.R. of China. Postal code 333001. Mobile/cellular phone : 86 13767818872 < RicSwenson0823@hotmail.com> http://www.jci.jx.cn/http://www.ricswenson.com
> Date: Sun, 27 Jul 2008 18:39:57 -0400> From: Sleighwhitaker@AOL.COM> Subject: Re: Crazing Hazards.. Let's do the math> To: CLAYART@LSV.CERAMICS.ORG> > In a message dated 7/27/2008 5:39:18 P.M. Eastern Daylight Time,> wendtpot@LEWISTON.COM writes:> > It turns out the gap is around 0.0000016 m. I Googled bacterial dimensions> and found the> average given is about 0.0000015 m on the narrow> axis for rod form bacteria.> I don't really have an opinion on the crazing issue. I like my stuff not to> craze for aesthetic reasons, but dishwasher temperatures kill most bacteria> and we do have immune systems that are made for this sort of thing). So I> guess you could put me in the camp that strives to avoid crazing, but I don't> see much potential for illness caused by it.> > I did want to point out a potential snag in your argument though. You are> using the average size of bacteria. Some bacteria are quite large (up to 2 um> in diameter or 2 x 10 E-6 m). While some like mycoplasma are quite small> (0.2um diameter or 2 x 10 E-7 m).> > You calculated the gap to be 0.0000016 m (or 1.6 x 10E-6 m). There is> about an order of magnitude difference between that and the smallest diameter for> bacteria (that leaves room for ~8 bacteria of Mycoplasma size to span a gap> of 1.6 x 10E-6 m). I'd also be hesitant to accept the size of the gap based> on calculations only as well. It would be very interesting if someone> actually measured craze gaps (which could be done on a nice microscope w/camera and> measuring functions). If I still worked in a lab I would attempt it, but I> don't. I would imagine that actual gap sizes could vary widely depending on> a lot of not very well defined variables.> > > Leigh Whitaker> visit my etsy shop at _http://www.leighwhitaker.etsy.com_> (http://www.leighwhitaker.etsy.com/)> visit my blog at _http://leighwhitaker.blogspot.com/_> (http://leighwhitaker.blogspot.com/)> > > > That leaves virtually> no room for growth, reproduction, circulation> of surrounding water to carry away wastes.> You get the picture. Craze lines are huge gaps> in the glaze when compared to water, oils, some> organic stains, but right on the boundary of> tight for average bacteria on the narrow axis> and way narrower than bacteria on the long> axis.> Concern for viruses is probably even lower> since they lack the motility of bacteria which> can move about either by pseudopodia or> flagella.> We have the tools at our disposal to figure> stuff like this out. Please, someone else run the> numbers and see if I am wrong.> Bottom line, bacteria may be able to fit> into the craze lines but it will be snug.> Larger species would not fit at all.> > > > (http://leighwhitaker.blogspot.com/)> > > > **************Get fantasy football with free live scoring. Sign up for> FanHouse Fantasy Football today.> (http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)
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Ric Swenson on mon 28 jul 08
The glaze technologists are at Alfred U. and Ohio State and JingdeZhen China....and.....
just ask someone....In whatever languages you know....
What do you want to know?
The American Ceramics Society is a real font of info....why not ask them for answers? They host this list and truly are accessible.
GOGGLE works wonders too..... The world is a big place and many study such stuff....
Regards,
Ric
"...then fiery expedition be my wing, ..." -Wm. Shakespeare, RICHARD III, Act IV Scene III Richard H. ("Ric") Swenson, Teacher, Office of International Cooperation and Exchange of Jingdezhen Ceramic Institute, TaoYang Road, Eastern Suburb, Jingdezhen City.JiangXi Province, P.R. of China. Postal code 333001. Mobile/cellular phone : 86 13767818872 < RicSwenson0823@hotmail.com> http://www.jci.jx.cn/http://www.ricswenson.com
> Date: Sun, 27 Jul 2008 17:10:25 -0500> From: wirerabbit2@GMAIL.COM> Subject: Re: Crazing Hazards.. Let's do the math> To: CLAYART@LSV.CERAMICS.ORG> > Hey Smarty Pants:> > So your theoretical model assumes what type of shape between faces?> Are these faces parallel or do they converge at some point below the> glaze's outer surface. Does glaze thickness determine how wide a craze> line will open? Do craze lines open and close any during the normal> use of functional ware?> > Thanks for the grounded evaluation. I'm diggin' it.> > Boy, I sure wish some other smarty pants like Dave F. would borrow an> electron microscope or something and do some actual measurements of> glaze fractures. Where's a ceramic technologist when you need one?> > Taylor, in Rockport TX, where he has to pour concrete in preparation> for framing in the garage. It's going to hurt...> > > On Sun, Jul 27, 2008 at 2:41 PM, Michael Wendt wrote:> > I set up a spreadsheet with 15 digit display to> > calculate the actual space that exists between> > the faces of the glaze discontinuities.> > I chose as a thermal expansion 6.0 x 10^-6> > I chose a temperature range of 280 degrees> > Celsius because in my experience crazing> > sounds do not occur until about that temperature> > if you open the kiln and let it crash cool.> > It turns out the gap is around 0.0000016 m.> > I Googled bacterial dimensions and found the> > average given is about 0.0000015 m on the narrow> > axis for rod form bacteria.> > ...
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Taylor Hendrix on mon 28 jul 08
Leigh:
You are very correct in pointing out that weakness. What I have fond
is that bacteria size will change depending on the speed of
reproduction, so I'm thinking an average bacteria size is going to be
as good as we get with this little exercise. Salmonilla seems to have
those aproximate sizes, however. I'm awfully bad with so many zeros
next to the decimal place so I could be way off on this.
Taylor, in Rockport TX
On Sun, Jul 27, 2008 at 5:39 PM, Leigh Whitaker wrote:
...
> I did want to point out a potential snag in your argument though. You are
> using the average size of bacteria. Some bacteria are quite large (up to 2 um
> in diameter or 2 x 10 E-6 m). While some like mycoplasma are quite small
> (0.2um diameter or 2 x 10 E-7 m).
>
...
Taylor Hendrix on mon 28 jul 08
Lee:
Your inputs in this thread relate only to the conversation you are
having with yourself in your mind.
Cracked kettle, cracked kettle cracked kettle! We need you to stay on
topic here in this thread.
I will however be interested in taking a look.
Taylor, in Rockport TX
On Sun, Jul 27, 2008 at 11:54 PM, Lee Love wrote:
> I heard an interesting interview with the author of __The Science Of
> Fear__. It relates to our discussion about crazing.
...
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