MudFire - Luba & Erik on sun 4 feb 07
Nancy Udell Wrote: Subject: Nitrite Bonded Sil Carbide Shelves
I feel I must respond to T. Robert's post (below) for the sake of
other electric kiln users who might be considering a purchase of the
nitrite bonded silicon carbide shelves marketed by Axner/ Laguna for
use in electic kilns...
Nancy, I've recently had a similar experience with Axner/Laguna, =
although with a different product. I purchased an $800 oxyprobe two =
years ago, placed it as directed into a 3/4" hole, put a bit kaowool =
around the exit hole, and left it there, undisturbed, untouched, =
unmoved. I have logs for the 20 medium-reduction cone 6 firings it has =
been through... before the platinum wire wore through and the oxyprobe =
stopped working in the middle of a firing. =20
A technician at Axner said it's not common for that to happen until the =
oxyprobe has been through 50-70 cone 10 firings at least and that the =
cost for a similar repair he just did was $260. I suggested that this =
was not the "nominal repair cost" that the oxyprobe users guide suggests =
and he offered to discuss this with Howard. Instead of Howard, I got a =
call from T. Roberts who went through a battery of questions about how =
the oxyprobe was used.
Here is what I found out from T. Roberts: 1.) The oxyprobe should not be =
used in a kiln with shino glazes since the soda ash will deteriorate the =
platinum wire! 2) In a downdraft kiln the oxyprobe should only be =
placed in the roof or the front wall of the kiln since backpressure will =
damage the oxyprobe! (mine was on the same back wall as the burners, =
but not in the burner's path. The readings were very consistent until =
it died). 3.) Platinum wire is expensive and "virtually indestructible" =
(huh?), therefore the implication is that the oxyprobe was moved in and =
out of the kiln and the wire was broken physically.
Here's what is says in the Axner users guide: 1. No warnings about =
shinos or atmospheric firings. No mention of virtually indestructible =
platinum being eaten up by a bit of soda ash on the 20 or so shino pots =
in the kiln. 2.) "If your probe is placed near or directly above your =
burner, you may experience significant fluctuations on your readings. =
This is not due to a flaw in the probe but rather it accurately reflects =
how the atmosphere is rapidly changing" (nothing about "your wire will =
break!") 3.) "If your probe is not producing reliable atmosphere =
information it is likely that this wire (that aforementioned =
indestructible platinum wire) has become brittle and has broken". The =
statement continues: "Simply return the probe to Axner for repair at =
nominal cost." =20
So... I'm at a crossroads here. If my oxyprobe gets up each night and =
slam-dances in the kiln room, there's nothing I can do. I certainly =
wouldn't have bought it had I known it shouldn't be used to fire shinos. =
And I can't move the oxyprobe - the kiln roof is many feet taller that =
the lead wire attached to the oxyprobe; and since my kiln is a shuttle, =
for technical reasons I cannot move it to the front. And since "nominal =
cost" seems to be upwards of 30% of the purchase price (I have to pay =
for shipping) at this rate, I'll be buying a new oxyprobe every 60 =
firings. I'll stand with Nancy... I could be wrong, but if the breakage =
was due to "atmosphere and firing schedule" or in my case "atmosphere =
and placement" then Laguna/ Axner needs to seriously change its =
marketing info on *several* of its products. It would have been nice to =
know these things up front.
Luba
MudFire Clayworks & Gallery
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175 Laredo Dr, Decatur, GA 30030
404-377-8033
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Kathi LeSueur on sun 4 feb 07
MudFire - Luba & Erik wrote:
>......I've recently had a similar experience with Axner/Laguna, although with a different product. I purchased an $800 oxyprobe two years ago, placed it as directed into a 3/4" hole, put a bit kaowool around the exit hole, and left it there, undisturbed, untouched, unmoved. I have logs for the 20 medium-reduction cone 6 firings it has been through... before the platinum wire wore through and the oxyprobe stopped working in the middle of a firing.
>
>A technician at Axner said it's not common for that to happen until the oxyprobe has been through 50-70 cone 10 firings at least and that the cost for a similar repair he just did was $260.>>
>
A much less expensive alternative to the Oxyprobe is the Bacarach Fyrite
CO2 analyzer. It can be purchased through Grainger. It's use is decribed
in the book "Getting into Pots" by George Wettlaufer. It is used to
measure combustion in oil burning furnaces and the only thing needed to
adapt it to a kiln is a quarz tube 15 inches long with an outside
diameter of 1/4 inch. While these can be purchased from Grainger, they
are exceedingly expensive from them (twenty years ago they were $70).
But, any glass studio making scientific equipment can make one up for
just a few dollars. I buy mine from Superior Glass in Ypsilanti, MI. I
buy five at a time (they break).
I've used this CO2 analyzer for about 25 years. I've replaced the unit
once in that time. Small seals like gaskets and diaphrams are about $50
dollars and should be replace about once a year. A low tech solution
that works and is much cheaper than the oxyprobe.
Kathi
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