Jonathan Pennington on mon 24 dec 01
* mstudios [011224 00:30]:
> Dear Clayarters--
>
> This may seem like a dumb question, but I'm perplexed. In the discussion
> thread about adding extra thickness to the walls of electric kilns (either
> with board or kaowool), both Craig Martell and Jonathan Pennington say they
> removed the stainless steel bands, added the extra insulation, and then
> re-fabricated/re-attached the steel bands.
>
> So, here's the question: why couldn't the extra insulation have gone around
> the outside of the stainless steel? Sort of like a water heater blanket,
> allowing for proper amounts of air intake etc? Is there a problem with
> having the stainless steel sandwiched between layers of insulation (is it a
> vapor barrier?) or is it just a matter of messy engineering problems (how to
> hold the second layer all together) without the steel bands on the outside?
Ha! So I'm not alone. I thought so too, but I tried it and got very
nasty results. First of all, you'd *really* risk melting things, trust
me on this one, I've got the molten metal to prove it :-). That
stainless is pretty tough (It only turned pretty colors), but what's
holding the stainless together are bands that are not high
temp. The'll melt, or seriously corrode, very very quickly. After that
one firing, I almost have to tack weld new bands onto the steel on
mine, because the screws and the screw holders started melting.
Also, You'd have to have something to hold the blanket on anyway. I
don't know that water heater blankets will withstand the temps on the
outside of a standard kiln, and I wasn't about to put kaowool (what I
used) around my kiln without something covering it. It just made more
sense to use the existing sheet to hold and cover the blanket.
And finally, my Skutt made doing this pretty easy. I was originally
afraid that the kilnMaster controller I have would cause problems, but
it turns out that it's built such that the element attachments and
thermocouple are attached to a *second* piece of steel, about an inch
away from the first piece. I basically removed that small outer piece
of steel, and it was easy for the inner piece to shift outward and
then hold the thermocouple and element attachments (I don't know if
this makes sense). Then I removed the kilnmaster, and have that
mounted off the kiln.
Anyway, for me, it wasn't an option. The risks of wrapping the kiln
were discovered when I *did* wrap the kiln and darn near ruined
it. Plus, once you actually say to yourself "Alright, I paid this much
money for this thing, but I'm going to destroy it anyway, here goes."
Then it's a surprisingly easy modification. I took photos of mine all
the way through, and am planning on posting a photo diary/howto on
modifying it so that people that come after can see that it's easy and
have a guide.
Whatever you decide, good luck.
-J
--
Jonathan Pennington | jwpennin@bellsouth.net
"There are no pots, there is only clay." -original
"It's hard to take life too seriously
when you realize yours is a joke." -also original
vince pitelka on wed 2 jan 02
> So, here's the question: why couldn't the extra insulation have gone
around
> the outside of the stainless steel? Sort of like a water heater blanket,
> allowing for proper amounts of air intake etc? Is there a problem with
> having the stainless steel sandwiched between layers of insulation (is it
a
> vapor barrier?) or is it just a matter of messy engineering problems (how
to
> hold the second layer all together) without the steel bands on the
outside?
Michael -
I have seen this done, but generally it is not a good idea, because the
stainless steel shell and associated hardware are subjected to excessive
heat. Also, the corrosive materials which outgas during firing concentrate
on the hardware and fittings beneath the fiber blanket, and under the higher
temperatures you would experience severe corrosion and metal failure far
sooner.
It really is not a difficult task to install a layer of fiberboard under the
stainless shell and then fabricate a sheet metal extension to re-fit the
shell.
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/
mstudios on wed 2 jan 02
Dear Clayarters--
This may seem like a dumb question, but I'm perplexed. In the discussion
thread about adding extra thickness to the walls of electric kilns (either
with board or kaowool), both Craig Martell and Jonathan Pennington say they
removed the stainless steel bands, added the extra insulation, and then
re-fabricated/re-attached the steel bands.
So, here's the question: why couldn't the extra insulation have gone around
the outside of the stainless steel? Sort of like a water heater blanket,
allowing for proper amounts of air intake etc? Is there a problem with
having the stainless steel sandwiched between layers of insulation (is it a
vapor barrier?) or is it just a matter of messy engineering problems (how to
hold the second layer all together) without the steel bands on the outside?
Thanks in advance for any insight on this.
Michael Shernick
Berthoud, CO
> With the added wall thickness I had to redo
>the stainless steel banding so all the electrical stuff had to come off
>anyway.
Marianne Lombardo on wed 2 jan 02
> So, here's the question: why couldn't the extra insulation have gone
around
> the outside of the stainless steel? Sort of like a water heater blanket,
Michael,
I was thinking of that same thing a while back. One of the kiln suppliers
that monitors this conference emailed me and said not to do it. It will
raise the outside wall temperature up to something like 1500 degrees.
I do lay a piece of kaowool on top of the lid and that seems to help slow
the cooldown a bit.
Marianne Lombardo
Omemee, Ontario, Canada
Craig Martell on wed 2 jan 02
Michael axed:
>So, here's the question: why couldn't the extra insulation have gone around
>the outside of the stainless steel?
Hello Michael:
The answer to the above question is: You'll burn the stainless and the
electrical components of the kiln too. There's a tremendous amount of heat
lost thru the k-23s and the steel jacketing of these kilns. My kiln was 3"
thick k-23s backed with an inch of Insblok 19. The 19 means it's rated to
1900 F. When the kiln was at cone 9 and above, the k-23s were totally
saturated and glowing bright red. Even at lower temps, this will destroy
the stainless and electrical stuff real fast.
regards, Craig Martell in Oregon
LOGAN OPLINGER on fri 4 jan 02
Dear Michael,
The stainless steel (SS) bands do act as somewhat of a vapor or "fume" barrier. Placing the SS between the insulating firebrick (IFB) and the ceramic fiber (CF) wool or board will cause the SS to be heated to a temperature much higher than if it is on the outside exposed to the air. An electric kiln also outgasses (breathes) fumes, some of which are corrosive, through the porous brick as well as through the joints and spyholes. The combination of the two (high temp. + fumes) causes the SS to corrode faster than if it is on the cooler outside. (I believe some of these fumes when they cool will also absorb moisture, thus even when the kiln is cool the corrosion can continue). Also, subjecting the SS to a higher temp. causes it to expand more, thus it looses its ability to compress and hold the IFB in place. The IFB can then shift out of position as the kiln expands and contracts during heating and cooling. This weakens the the integrity of the kiln, causing, among other problems, the joints to open up and leak heat, and accelerating the self destruction of the kiln.
(The outside of an electric or gas water heater does not get as hot as the outside of an electric kiln, and there are no fumes passing through the wall of a water heater).
It should be noted that in original construction with the SS bands on the outside, some corrosion occurs over time (8 - 10 years) on the side of the SS bands against the IFB. I have observed several kilns hear that have fallen apart because of this. By placing CF insulation between the SS bands and the IFB means the outside of the kiln will be cooler, thus subjecting the SS less to the corrosive effects of the fumes coming through the IFB walls.
I hope this helps.
Logan Oplinger
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Michael Shernick wrote:
>Dear Clayarters--
>This may seem like a dumb question, but I'm perplexed. In the discussion
thread about adding extra thickness to the walls of electric kilns (either
with board or kaowool), both Craig Martell and Jonathan Pennington say they
removed the stainless steel bands, added the extra insulation, and then
re-fabricated/re-attached the steel bands.<
>So, here's the question: why couldn't the extra insulation have gone around
the outside of the stainless steel? Sort of like a water heater blanket,
allowing for proper amounts of air intake etc? Is there a problem with
having the stainless steel sandwiched between layers of insulation (is it a
vapor barrier?) or is it just a matter of messy engineering problems (how to
hold the second layer all together) without the steel bands on the outside?<
>Thanks in advance for any insight on this.<
>Michael Shernick<
>Berthoud, CO<
--
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