Pyrometric device
Encyclopedia
Pyrometric devices gauge heatwork
(the combined effect of both time and temperature) when firing materials inside a kiln
. Pyrometric devices do not measure temperature, but can report temperature equivalents. In principle, a pyrometric device relates the amount of heat work on ware to a measurable shrinkage or deformation of a regular shape.
Care should be taken with the interpretation, as some naively assume they are a measure of temperature alone.
Bars
Cones
and Shanxi
have reported that pyrometric cones about five centimetres tall and made from loess
were used to help control the firing of the kilns .
In 1782, English potter and industrialist Josiah Wedgwood
created accurately scaled pyrometric device, with details published in the Philosophical Transactions of the Royal Society of London in 1782 (Vol. LXXII, part 2). This led him to be elected a fellow of the Royal Society
.
The modern form of the pyrometric cone was developed by the German ceramics technologist Hermann Seger and first used to control the firing of porcelain wares at the Königliche Porzellanmanufaktur (Royal Porcelain Works) in Berlin, in 1886. Seger cones are to this day made by a small number of companies and the term is often used in Europe as a synonym for pyrometric cones.
Holdcroft Bars were developed in 1898 by Holdcroft & Co.
Bullers rings have been in continuous production for over 80 years, and are currently in use in over 45 countries. The manufacturers, Taylor Tunnicliff Limited, were founded in 1867.
The Standard Pyrometric Cone Company was founded by Edward J. Orton, Jr. in 1896. Following the death of Dr Orton in 1932, a charitable trust was established to ensure the continued operation of the company, for the benefit of the ceramic arts and industry.
Heatwork
Heatwork is the combined effect of temperature and time. It is important to several industries:*Ceramics*Glass and metal annealing*Metal heat treating...
(the combined effect of both time and temperature) when firing materials inside a kiln
Kiln
A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...
. Pyrometric devices do not measure temperature, but can report temperature equivalents. In principle, a pyrometric device relates the amount of heat work on ware to a measurable shrinkage or deformation of a regular shape.
Care should be taken with the interpretation, as some naively assume they are a measure of temperature alone.
Types
Rings- Are flat, hollow centred rings whose contraction is proportional to the heat work experienced. A micrometer or gauge measures the fired ring, with the difference being an arbitrary number that is used to describe the firing regime experienced. Various grades of ring, each of slightly different compositions, are available to cover all firing conditions and temperature equivalents likely to be encountered. Examples of pyrometric rings include Bullers Rings, PTCR Rings and Thermorings.
Bars
- Are square, sectioned bars held horizontally across two fixed distance supports. During firing the softening of the material results in sagging at the center. Pyrometric Bars have found popularity in Kiln Sitters, which uses the described deformation to act as a triggering element, thus turning off the kiln at a desired point of maturity. An example is the Holdcroft Bar.
Cones
Pyrometric cone
Pyrometric cones are pyrometric devices that are used to gauge heatwork during the firing of ceramic materials. The cones, often used in sets of three as shown in the illustration, are positioned in a kiln with the wares to be fired and provide a visual indication of when the wares have reached a...
- Are slender, three sided pyramids made from a range of compositions each with a reference number corresponding to a certain heat work. Rather than shrink as rings do, a cone's tip will bend forward to the same level as the base at the time of maturity. Other deformation of a cone, such as bloating, cracking, or bending backward, can be appropriately interpreted to troubleshoot activity inside the kiln.
History
Archaeologists working at Northern Song period (960 to 1127 AD) kiln sites in the Chinese provinces of ShaanxiShaanxi
' is a province in the central part of Mainland China, and it includes portions of the Loess Plateau on the middle reaches of the Yellow River in addition to the Qinling Mountains across the southern part of this province...
and Shanxi
Shanxi
' is a province in Northern China. Its one-character abbreviation is "晋" , after the state of Jin that existed here during the Spring and Autumn Period....
have reported that pyrometric cones about five centimetres tall and made from loess
Loess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...
were used to help control the firing of the kilns .
In 1782, English potter and industrialist Josiah Wedgwood
Josiah Wedgwood
Josiah Wedgwood was an English potter, founder of the Wedgwood company, credited with the industrialization of the manufacture of pottery. A prominent abolitionist, Wedgwood is remembered for his "Am I Not A Man And A Brother?" anti-slavery medallion. He was a member of the Darwin–Wedgwood family...
created accurately scaled pyrometric device, with details published in the Philosophical Transactions of the Royal Society of London in 1782 (Vol. LXXII, part 2). This led him to be elected a fellow of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
.
The modern form of the pyrometric cone was developed by the German ceramics technologist Hermann Seger and first used to control the firing of porcelain wares at the Königliche Porzellanmanufaktur (Royal Porcelain Works) in Berlin, in 1886. Seger cones are to this day made by a small number of companies and the term is often used in Europe as a synonym for pyrometric cones.
Holdcroft Bars were developed in 1898 by Holdcroft & Co.
Bullers rings have been in continuous production for over 80 years, and are currently in use in over 45 countries. The manufacturers, Taylor Tunnicliff Limited, were founded in 1867.
The Standard Pyrometric Cone Company was founded by Edward J. Orton, Jr. in 1896. Following the death of Dr Orton in 1932, a charitable trust was established to ensure the continued operation of the company, for the benefit of the ceramic arts and industry.