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Min

Member Since 31 Mar 2010
Offline Last Active May 20 2015 05:10 PM
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Topics I've Started

New Elements

19 May 2015 - 09:24 PM

I was doing some reading on Kanthal and came across the blurb below. After replacing elements I have always run the kiln empty up to around ^04 then shut it off but am wondering how significantly element life is improved if held for the 7 to 10 hours as recommended by Kanthal. Does anybody do this and have you found an increase in element life?

 

From the Kanthal Handbook, referring to their FeCrAl alloys (i.e. A-1 alloy):

 

"The durability of resistance alloys in air at high temperatures is greatly increased by an oxide surface layer formed by a reaction with the oxygen of the air. The protective nature of this oxide layer is proportional to its area and depth. Foreign matter usually interferes with the formation of the oxide layer, and this causes a reduced life. ... At high temperatures the protective layer of Kanthal materials consists almost entirely of aluminum oxide. This has a light grey colour and good chemical resistance. At temperatures below 1000oC (1832oF) the oxide layer has a dark colour since the aluminum oxide is impure."

In order to protect elements from the effects of harsh environments, it is very desirable to condition the elements, by pre-oxidizing them. This is accomplished by firing them to a temperature of 1050oC/1922oF and soaking for several hors, 7-10 if possible. The process is enhanced by allowing good air flow into the kiln - leave the peepholes open, or the KilnVent on. If you are doing reduction firings in an electric kiln it is desirable to periodically re-oxidize the elements, for best life expectancy. The results of element conditioning can be quite dramatic. It may not have much affect for normal, low temperature firings, but can be significant for harsh operating conditions."

 

 

 

 


Rolling Pins

12 May 2015 - 02:40 PM

Came across this site on Etsy for laser carved rolling pins. The larger ones are approx 2 1/2" diameter X 10" rolling surface. Nice to see some alternatives to the ones at potters supply stores. (there are 3 pages of designs, sets of small rollers plus the larger ones)

il_570xN.711475726_97m1.jpg


Old Orton Controller

09 May 2015 - 03:40 PM

I just picked up a spare kiln. It's from Pottery Supply House (Euclids) and  has never been used. It came with an Orton Autofire controller. Very basic touchpad, the manual that came with it is dated 1993. Anybody use one of these controllers? I'm thinking of switching the touchpad to a Skutt or Bartlett one. Any thoughts? 

Attached File  photo.jpeg   27.95KB   0 downloads

 

 

 


Iron Speckles

05 April 2015 - 10:45 AM

I have 2 glazes with the same colourants, 1 results in a amber colour with no iron speckles, the other is full of speckles. Same claybody, firing schedule used for both glazes. I know I could probably ball mill the speckled one but I'm wondering what is causing the iron to agglomerate in the glaze? ^6 electric, low coe glazes.

 

no iron speckles recipe:                                                

Tea                                                                           
Silica 23.00                                                                   
EP Kaolin 14.00
Nepheline Syenite 10.00
Frit 3195 16.60
3134 4.80
Australian Spodumene 15.00
Dolomite 15.00

Bentonite 2.00
Manganese Dioxide 3.00
Iron Oxide Red 2.00
105.40

 

Speckles

Silica 34.50
Wollastonite 5.00
EP Kaolin 23.00
Minspar  12.00
Gerstley Borate 22.00
Talc 3.00
Dolomite 3.00
Nepheline Syenite 2.90

Manganese Dioxide 3.00

Iron Oxide Red 2.00

 

 

I don't think the higher silica levels in the second recipe is the culprit, I'm thinking the lithia in the first recipe might have something to do with it? Boron differences?

Any thoughts most welcome.


China Marker

31 March 2015 - 03:43 PM

Thought I would share what I have found to work for marking test tiles easily and cheaply. The Dixon (Hi-Heat) China Marker pencil in brown lasts through ^7 oxidation firings on my test tiles. It stays clear and legible and is way cheaper than the ceramic underglaze pencils. ($7- for a dozen china pencils on Amazon versus around $12 for one ug pencil)  It's kind of waxy so doesn't smear or rub off if you wipe glaze drips off bottom of test tiles. It doesn't leave any ghost marks on the kiln shelves.

 

It does burn out with glaze overtop but for test tiles it's brilliant. Haven't fired it hotter than ^7 so don't know if it will do ^10 but I think it would.

 

 CHH%20Brown%20China%20Markers-500x500.jp