Roger Korn on mon 6 may 02
I think the blacksmiths are thinking of brittle failure from thermal shock,
whereas
the usual hob failure is due to erosion by oxidation. The oxide coat that
builds up
on the bars should not be disturbed - it protects the iron beneath from
further
oxidation.
Roger
vince pitelka wrote:
> > John & all... I spoke with some of my Blacksmith friends yesterday
(while
> > at the Sanford Pottery Festival).... I figured if we've got a question
ask
> > the experts! Their response was as long as it was NOT High Carbon Steel
> or
> > in other words, "Tool Steel", there is no problem with hosing down the
> > grate, even dropping it in a tub of cold water. It won't cause it to
> > deteriorate any faster, nor stress the metal.
>
> Sorry Karen, but your blacksmith friends are mistaken. It is
understandable
> that they would not understand this situation. The superheated iron
builds
> up a thick layer of completely and partially oxidized iron, which helps
> insulate the sound interior core from further oxidation. Every time you
> hose off the iron or immerse it in water it sheds the exterior layer of
> oxide, and the next time you fire the kiln the grate bars oxidize that
much
> deeper, drastically shortening their life. I would avoid ever hosing them
> off for any reason. Better to leave them in there when the firebox gets
> sealed up.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> Home - vpitelka@dtccom.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> http://www.craftcenter.tntech.edu/
>
>
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Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
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Karen on mon 6 may 02
John & all... I spoke with some of my Blacksmith friends yesterday (while
at the Sanford Pottery Festival).... I figured if we've got a question ask
the experts! Their response was as long as it was NOT High Carbon Steel or
in other words, "Tool Steel", there is no problem with hosing down the
grate, even dropping it in a tub of cold water. It won't cause it to
deteriorate any faster, nor stress the metal.
High Carbon Steel, or "tool steel" is different, it can actually shatter by
stressing it in such a manner. Much like taking a red hot pot & dropping it
in icey cold water.... Or pouring icey cold water in a hot ceramic item....
it's gonna shatter....
>I have a question for any metal, iron, and steel gurus
> that may be out there in Clayart land. My friend David
> has a firebox grate made from metal rods in his pseudo
> fast-fire wood burning kiln. Being in a high traffic
> tourist area, when the firing is over, he pulls out
> the grate, and hoses it down. He is worried that a
> child or curious adult will get burned on the hot
> grate. The question, is he damaging the grate by
> spraying water on the sometimes glowing red grate? Any
> comments or suggestions are welcome. Thank you. John
> Horner, newbie clayarter as well as new to ceramics.
vince pitelka on mon 6 may 02
> John & all... I spoke with some of my Blacksmith friends yesterday (while
> at the Sanford Pottery Festival).... I figured if we've got a question ask
> the experts! Their response was as long as it was NOT High Carbon Steel
or
> in other words, "Tool Steel", there is no problem with hosing down the
> grate, even dropping it in a tub of cold water. It won't cause it to
> deteriorate any faster, nor stress the metal.
Sorry Karen, but your blacksmith friends are mistaken. It is understandable
that they would not understand this situation. The superheated iron builds
up a thick layer of completely and partially oxidized iron, which helps
insulate the sound interior core from further oxidation. Every time you
hose off the iron or immerse it in water it sheds the exterior layer of
oxide, and the next time you fire the kiln the grate bars oxidize that much
deeper, drastically shortening their life. I would avoid ever hosing them
off for any reason. Better to leave them in there when the firebox gets
sealed up.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Karen on tue 7 may 02
>Sorry Karen, but your blacksmith friends are mistaken. It is
understandable
> that they would not understand this situation. The superheated iron
builds
> up a thick layer of completely and partially oxidized iron, which helps
> insulate the sound interior core from further oxidation. Every time you
> hose off the iron or immerse it in water it sheds the exterior layer of
> oxide, and the next time you fire the kiln the grate bars oxidize that
much
> deeper, drastically shortening their life. I would avoid ever hosing them
> off for any reason. Better to leave them in there when the firebox gets
> sealed up.
well Vince, that certainly makes sense to me.... I agree understandable
that they might not understand the situation as they are working the metals
continually, even after the immersion in water.... so I would suspect that
the oxidation would either not be occuring when they work them in that
manner as you explained above or it would be worked out of the metal they
are using (educated guessing here.... since it's late & I'm tired & not
entirely sure my fingers are typing what's going on in my brain...) I may
also not have explained very well, it had been a few days since I had read
the post... when I saw them I thot I ought to ask....
Glad for the clarification.... Thanks!
Karen
(in/near Raleigh, but who thinks she knows the -seagrove- potter who does
this...)
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