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Kilns

Tetlow Kilns Specifications - sizes etc

Choosing a Kiln:

The choice of a kiln is seldom a simple one involving many considerations
The practical decisions are as follows:
1. What type of work is being produced?
As a guideline we suggest the following:

PURPOSE

Electric

Gas

China painting

X

 

Earthenware only

X

 

Porcelain & Stoneware

X

X

Earthenware, Stoneware & Middle Fire

 

X


 

Electric

Gas

Oxidation Firing

X

 

Reduction Firing

 

X

Reduction firing in gas kilns allows for greater colour experimentation and versatility in firing results.
2. Volume to be fired.
3. Maximum firing temperature.
4. Control equipment required.
5. Site location.
6. Hood venting position with flues.
7. Type of Floor.
8. Adequate space for door opening, loading & to keep combustible material clear.
9. Electricity supply available (often 2 & 3 phase)

 

Top
Loading

Front
Loading

Electric

X

X

Gas

 

X

All the above need to be considered to in order to make the best and most economic long term decision in buying your kiln.
Walker Ceramics will be happy to advise and quote on supplying a kiln package to meet your requirements.
ELECTRIC KILNS - TETLOW
We supply Tetlow Electric Kilns which are manufactured using K23 hot face insulating bricks backed up by insulating materials. They are fitted with a safety switch (to automatically shut down if the door is opened), energy regulator, warning light and Kanthal A1 elements- approved by the Electrical Supply Companies. The energy regulator controls the rate of temperature increase. It is a control knob with a scale of 0-100. If the knob is turned to 100, the kiln will heat at its maximum rate. If it is turned up to 50, the Kiln will heat 50% of the time. It is a very useful piece of equipment as the rate of temperature increase can be easily controlled. For instance, if thick walled pots were being fired, the rate of temperature increase could be reduced to 10% for the first hour, then increased to 25% for the second hour etc. All the kilns listed may be fitted with either a front loading swing door, or a top loading drop down door: however we list which type is supplied as standard.

GAS KILN INSTRUMENTS 
Pyrometers & Thermocouples There are two ways of measuring temperature during the firing- by pyrometers or pyrometric cones. They are often used together as they perform different functions. Pyrometers measure temperature, cones measure heat work.
A pyrometer is an instrument fixed outside the kiln which shows by way of a needle on a scale of degrees the temperature inside the kiln. Attached to the pyrometer is a lead which in turn is attached to the thermocouple which projects inside the kiln. The thermocouple generates the current which is measured by the pyrometer.
The thermocouple consists of two different metals joined together at one end covered by a cylindrical sheath. These metals are either: 1.C/A (Chrome -Alumel) for temperatures up to 1200C 2.R/M ( Rare metals-generally Platinum & Rhodium) for temperatures up to 1400C.
We sell these instruments individually as follows. Digital Pyrometer Model 1314 Temperature Range 0 -1400C and suits all Thermocouples.

 Thermocouple 23cm C/A 1200C Thermocouple 23cm R/M 1400C Thermocouple 30.5 R/M 1400C (we can supply longer if required) 

1.8 metre lead to suit C/A couple (Yellow) 1.8 metre lead to suit R/M couple (Green) 

FIRING YOUR ELECTRIC KILN FOR THE FIRST TIME.
Once you have unpacked your kiln and all its furniture, you must consider where you are going to position it. There are several issues related to safety when making your decision.
Your kiln should be kept a minimum of 60 cm from all walls, except in the case of brick walls, where at least 30 cm is recommended.
The kiln should stand on a fire retarding surface such as a concrete slab or floor.
We recommend that the electrical supply to your kiln is fitted with an isolation switch so that the supply can be switched off quickly, in case of an emergency.
Adequate ventilation is essential when firing. This can be supplied through an open window, exhaust fans or ventilation system. Ventilation is necessary to prevent the build up of fumes produced as a by-product of firing. These fumes can be in the form of gases, steam, lead vapours, acid vapours depending upon the clay bodies and glazes being fired.
It is recommended that the first firing of a new kiln is a slow firing, with the kiln empty, to a temperature 10% - 15% less than the maximum temperature of the kiln (approx. 1100 degrees Celsius ; cone 03). This is to enable the cement to mature and to remove any moisture from the brickwork.
To commence your dry-out firing, fit cone 03 into cone stand, close kiln door and check that the cone stand is still set. Turn on energy regulator to 10% and fire kiln for 8 hours, then turn regulator to 30% for 6 hours . Then turn regulator to 60% for 6 hours and finally turn regulator to 100% for a further 4 hours.
Do not open your kiln until it has cooled completely.
After a few firings, the dark stains now present in your kiln will disappear.
While the kiln is firing, we recommend that you apply kiln wash to all kiln furniture to prevent pieces sticking during firing.
Should you have any problems or require further information, please do not hesitate to contact us.
We know that you will produce wonderful ceramic pieces in your new kiln and also feel that sense of pride in having made it yourself.
Have fun and bring in your work to show us, we love to see it!

 

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Copyright 2010 David Walker / Ozclay Pty. Ltd. All rights reserved.
Revised: December 22, 2010 .