Heather Morris on wed 17 nov 04
OK, I'll try again. Somewhere in the vastness of the US of A there must =
be someone who knows the answer to this question to make my overloaded =
inbox worthwhile.
Some of my pit-fired pots have got excessive black shiny carbon marks on =
them which spoil them, though the other coppery markings are good. So I =
want to experiment with refiring them in the electric kiln to burn out =
the blackening whilst hopefully retaining some of the other markings. If =
it doesn't work I don't mind taking the risk. I want to find a few =
guidelines for experimentation, e.g.
1. What temperature would the kiln need to be at to make e.g.a piece of =
paper/wood inside it spontaneously ignite?
2. What happens to the smoke/carbon produced by that ignition? Does it =
remain in the kiln, get released as smoke/gas into the outside air/ turn =
into a different form/ get redeposited? If it turns into something else, =
what, and at what temperature?
I need to know, so I can experiment with the lowest possible temps to =
get rid of the blackening. If I have some guidelines I'll waste less =
electricity on the experiments!
Carl Finch on fri 19 nov 04
At 12:50 PM 11/19/2004, mailtoandrew@FSMAIL.NET wrote:
>... 1. What temperature would the kiln need to be at to make e.g.a piece
>of paper/wood inside it spontaneously ignite? ...
>
>I think Ray Bradbury this best one to answer this.
Perhaps, but I don't think he's a member of Clayart.
However I do recall that Mr. Bradbury wrote a short story having to do with
firemen whose job it was to set fire to books. He titled it "Centigrade
232.777..." but it never sold well.
I believe the publisher finally convinced him to change the name to
something else, but I forget just what.
--Carl
in Medford, Oregon
mailtoandrew@FSMAIL.NET on fri 19 nov 04
... 1. What temperature would the kiln need to be at to make e.g.a piece
of paper/wood inside it spontaneously ignite? ...
I think Ray Bradbury this best one to answer this.
Regards,
Andrew
Vince Pitelka on sat 20 nov 04
You wrote:
> "It was Fahrenheit 451 and if I recall correctly, Bradbury took this title
> from the from the temperature at which books burn. The title was later
> hijacked by Michael Moore. But my point is that maybe 451 F is the point
> at which paper would ignite in a kiln."
Yes it is true that Michael Moore tastefully and appropriately adapted
Bradbury's title in his powerful film.
451 Fahrenheit is the kindling temperature of organic fuels - wood, paper,
coal, gasoline, etc. That means that if the temperature is elevated to 451
fahrenheit, the exothermic (heat-producing) combustion reaction will then
sustain itself. As we all know, the speed of combustion has to do with the
exposed surface area in the fuel. The kindling temperature applied to the
fuel, via a match, glowing coal, spark-plug, pilot light, etc., simply
creates the opportunity for combustion. If there isn't much exposed surface
area, as in split firewood, then it takes a lot of "kindling." If there is
lots of exposed surface area, as in a gas, then it just takes a millisecond
spark to initiate a self-sustaining (and instantaneously-accelerating)
combustion reaction.
When you discharge a fire extinguisher at the base of a fire, it simply
starves the combustion reaction of oxygen, causing the fuel to drop below
it's kindling temperature. If you stop discharging the fire extinguisher
before the fuel cools below 451 Fahrenheit, it will burst back into flames.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Vicki Hardin on sat 20 nov 04
It was Fahrenheit 451 and if I recall correctly, Bradbury took this title from the from the temperature at which books burn. The title was later hijacked by Michael Moore. But my point is that maybe 451 F is the point at which paper would ignite in a kiln.
>I think Ray Bradbury this best one to answer this.
>
> Perhaps, but I don't think he's a member of Clayart.
>
> However I do recall that Mr. Bradbury wrote a short story having to do with
> firemen whose job it was to set fire to books. He titled it "Centigrade
> 232.777..." but it never sold well.
>
> I believe the publisher finally convinced him to change the name to
> something else, but I forget just what.
Vicki Hardin
http://ClayArtWebGuide.com
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
Wayne on sat 20 nov 04
Farenheit 451
So much for leaving an impression .
Wayne seidl
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Carl
Finch
Sent: Friday, November 19, 2004 9:38 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: ignition/vaporisation temperatures
At 12:50 PM 11/19/2004, mailtoandrew@FSMAIL.NET wrote:
>... 1. What temperature would the kiln need to be at to make e.g.a
piece
>of paper/wood inside it spontaneously ignite? ...
>
>I think Ray Bradbury this best one to answer this.
Perhaps, but I don't think he's a member of Clayart.
However I do recall that Mr. Bradbury wrote a short story having to
do with
firemen whose job it was to set fire to books. He titled it
"Centigrade
232.777..." but it never sold well.
I believe the publisher finally convinced him to change the name to
something else, but I forget just what.
--Carl
in Medford, Oregon
____________________________________________________________________
__________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your
subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
pdp1@EARTHLINK.NET on sat 20 nov 04
Hi Wayne,
Or...in other ways-of-faith...
451 ° Fahrenheit, being as...
232.778 ° Celsius
505.928 kelvin
910.67 ° Rankine
186.222 ° Réaumur
Or, what in Baking...they used to call...a 'quick' Oven.
Phil
el ve
----- Original Message -----
From: "Wayne"
Farenheit 451
So much for leaving an impression .
Wayne seidl
Marcia Selsor on sat 20 nov 04
I always used paper in a gas kiln to tell me when it was below F. 451
so I could start unbricking the door.
I figured if it was below quartz inversion (F. 500) then is was safe to
start cooling.
Marcia Selsor
a bright sunny day in Montana with white snowy ground everywhere
Ron Roy on sun 21 nov 04
The quartz inversion is at 573C not F by the way.
471F is 244C
I also used to use the scorched paper guide to see when it is OK to crack a
kiln.
Using paper can be a problem by the way - 244C is above the temperature of
the cristobalite conversion. For clays with cristobalite in them - it could
be a disaster - for the same reason cristobalite should be absent in
ovenware
It also depends on what kind of kiln however - big kilns with lots of heat
retaining refractories need some help cooling - but I would not recommend
cracking an electric kiln at that temperature.
>I always used paper in a gas kiln to tell me when it was below F. 451
>so I could start unbricking the door.
>I figured if it was below quartz inversion (F. 500) then is was safe to
>start cooling.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on sun 21 nov 04
Woops - let me try that again!
The quartz inversion is at 573C not F by the way.
451F is 232C
I also used to use the scorched paper guide to see when it is OK to crack a
kiln.
Using paper can be a problem by the way - 232C is above the temperature of
the cristobalite conversion. For clays with cristobalite in them - it could
be a disaster - for the same reason cristobalite should be absent in
ovenware
It also depends on what kind of kiln - big kilns with lots of heat
retaining refractories need some help cooling - but I would not recommend
cracking an electric or fiber kiln at that temperature.
>I always used paper in a gas kiln to tell me when it was below F. 451
>so I could start unbricking the door.
>I figured if it was below quartz inversion (F. 500) then is was safe to
>start cooling.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Louis Katz on sun 21 nov 04
Farenheit 451 is not a constant for all things organic. All of this
depends on many things. Some organic fuels light at lower temperatures.
Others such as carbon require much hotter temperatures . The kindling
temperature of paper appears to depend on its clay content. The more
clay the more heat it seems to take to make the papers combustion self
supporting. Teflon is organic but does not burn at 451. This discussion
should include an authoritative definition of flash point as well as
kindling temperature if there is a difference. Something I am not
competent to give. Heating something slowly to 451 is different than
heating it quickly as when you heat it slowly, with some things such as
paper you drive off the more volatile and easier to burn components
first. When you finally reach your normal combustion temperature there
is not much to burn.
Flash point is the temperature that something has to be heated to in
order ofr it to be ignited by a lit match held above it. How hot does
the lit match have to be?
Needed: Someone with lots more knowledge of combustion.
Louis
On Nov 20, 2004, at 6:20 PM, Vince Pitelka wrote:
> 451 Fahrenheit is the kindling temperature of organic fuels - wood,
> paper,
> coal, gasoline, etc
http://www.tamucc.edu/wiki/Katz/HomePage
Janet Kaiser on sun 21 nov 04
As a matter of interest, what precisely is meant by everyone,
including Mr. Bradbury? Knowing how extremely difficult it is to
set fire to a book or any number of sheets of paper (whether
bound or not) there is really quite a big difference between
"ignite" and "burn". Surely self ignition would not happen at 451
=B0F? Maybe a single sheet at a pinch, but surely not a book?
Anyone willing to try? Not me! I spent yesterday evening cleaning
the oven (second attack in a month). If anyone had told me I
would spend a Saturday night doing that 20 years ago, I would
have thought them mad...
Sincerely
Janet Kaiser -- who said "get a life"????
*** IN REPLY TO THE FOLLOWING MAIL:
>It was Fahrenheit 451 and if I recall correctly, Bradbury took
this title
>from the from the temperature at which books burn. The title
was later
>hijacked by Michael Moore. But my point is that maybe 451 F is
the point
>at which paper would ignite in a kiln.
>*** THE MAIL ENDS HERE ***
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The Chapel of Art : Capel Celfyddyd
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Home of The International Potters' Path
Tel: ++44 (01766) 523570 http://www.the-coa.org.uk
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Vicki Hardin on sun 21 nov 04
As to whether Michael Moore tastefully and appropriately adapted Ray Bradbury's work or hijacked it, I will defer to Ray Bradbury. Hijacked is one of Bradbury's own words and I further quote his response to this incident:
"He stole my title and changed the numbers without ever asking me for permission."
I don't see this as any different than when Mel has referred to finding close approximations of his work on the cover of magazines by other people taking credit. If we support the taking of other peoples work, where will it end?
Here's more on the article for those interested. http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=38776
> Yes it is true that Michael Moore tastefully and appropriately adapted Bradbury's title in his powerful film.
>
Best Regards,
Vicki Hardin
http://ClayArtWebGuide.com
Hal Giddens on mon 22 nov 04
>
> From: Vicki Hardin
> Date: 2004/11/21 Sun PM 08:31:42 EST
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: ignition/vaporisation temperatures
>
> As to whether Michael Moore tastefully and appropriately adapted Ray Bradbury's work or hijacked it, I will defer to Ray Bradbury. Hijacked is one of Bradbury's own words and I further quote his response to this incident:
>
> "He stole my title and changed the numbers without ever asking me for permission."
>
> I don't see this as any different than when Mel has referred to finding close approximations of his work on the cover of magazines by other people taking credit. If we support the taking of other peoples work, where will it end?
>
> Here's more on the article for those interested. http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=38776
>
> > Yes it is true that Michael Moore tastefully and appropriately adapted Bradbury's title in his powerful film.
> >
> Best Regards,
> Vicki Hardin
Thank you Vicki.
Hal Giddens
Home Grown Pottery
Rockledge, Georgia USA
kenhal@bellsouth.net
mailtoandrew@FSMAIL.NET on tue 23 nov 04
Hello All,
Im not sure if I should be pleased or embarrassed as to the extent of the
debate my flippant reply to Heather=92s initial question about the
temperature at which paper would spontaneously ignite ... it was just a
light hearted comment!
Anyway ... the title of Ray Bradburys book is taken from the self ignition
temperature of paper, i.e. get it to that temperature and it will
spontaneously ignite. However, and no criticism of Mr. Bradbury who
presumably didn=92t mean this as a reference standard, such a temperature
can not be universal.
Paper is not paper! Meaning ... just think of the many different types of
paper we use everyday: tissues, newspapers, magazines, writing paper,
photocopier paper, photo printer paper, etc. A significant difference
across these is the amount of the non wood pulp content. One of the most
popular filler and coating materials is kaolin and, depending on grade,
may represent between 2 and 30% of the mass of paper.
So, in addition to the surface area, as previously mentioned by Vince, the
amount of clay, or other minerals, used will influence the self ignition
temperature. Therefore 451 degrees Fahrenheit may not be the correct value.
And as an aside ... both Metric and Imperial units have been quoted in
this post: whilst it is recognised that the US stands almost alone in its
use of Imperial units it is less well known that the ultimate base of its
weights and measures is the SI system. Since 1893 units have been defined
in Metric terms: for example pounds defined by kilogrammes and yards by
meter.
Thats enough rambling ....
Regards,
Andrew
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