Thermal Gradient Furnace

The Orton Gradient Furnace is the most powerful and most cost effective laboratory instrument for studying the reactions of a material as a function of temperature. In one firing, the Orton Gradient Furnace thermally processes and prepares a series of samples with known thermal histories for measuring and studying the effects of temperature on their reactions and physical properties. After one firing, you can study the effects of a temperature range on properties such as shrinkage, sintering, density, porosity, absorption, surface area, color, degree of crystallization, phase development, electrical properties, magnetic properties, and others. Orton Gradient Furnaces are made for operation between room temperature and 1,600°C.

Place an extruded column of a green ceramic, a row of pressed discs or parts, a trough of granular raw material, or a glazed substrate on the D-tube hearth and into the Orton Model GTF-MD-16 Gradient Furnace. Set the controller for a specific thermal cycle, them walk away to perform other tasks. After the furnace cools, remove the samples and record their position on the D-tube hearth. Since one end of the row of materials was cooler then the other, you can immediately see how the range of firing temperatures affected the shrinkage, color, porosity, particle size, degree of vitrification, and other ceramic properties that are temperature dependent. And do it in ONE firing !!!




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The Orton Model GTF-MD-16 (1,600°C maximum) Furnace is a specially designed horizontal tube furnaces with controlled, reproducible, linear thermal gradients of approximately 120°C across a 12" long monitored zone. The Orton Model GTF-MD-16L Furnace is a longer versions with controlled, reproducible, linear thermal gradients of approximately 160°C across a 16" long monitored zone. Thermocouples on 2" centers monitor the temperatures along the gradient zone, so the temperature of the material at any position along the D-tube hearth is known. Visual or post firing analyses of sections taken from the fired material at any position along the D-tube hearth can be measured, recorded, and studied as a function of temperature.


The Model GTF-MD-16 furnace is a rectangular, metal shell structure that houses the refractory fiber insulation and four molybdenum disilicide heating elements that surround one end of the 2 7/8” ID ceramic heating chamber tube. The samples to be fired are placed on the top of the 2.5” wide high alumina D-tube hearth, which rests on the bottom of the ceramic heating chamber tube. Type “S” thermocouples are spaced on 2” centers along the monitored zone and extend vertically through the top of the heating chamber tube. Two specially shaped IFB end plugs are included to cover both ends of the furnace.



The furnace temperature is controlled by the Universal Temperature Control Console (UTC), the lower right cabinet in the photo. The UTC contains the user programmable, multi-segment PID controller, the phase-angle-fired SCR solid state power module, ammeter, ON/OFF power switch and appropriate electrical receptacles. The PID controller uses the thermocouple at the hot end of the furnace for control, so the monitored gradient falls from this control temperature. Electrical power from the UTC runs through the included step-down transformer (included, but not shown in the photo) and on to the molybdenum disilicide heating elements.

The Temperature Display Cabinet (smaller cabinet on top of the UTC) contains a digital panel display, rotary selector switch and appropriate electrical receptacles to display the temperatures of the other thermocouples along the length of the monitored zone. The system includes all interconnecting cables and instruction manual.


Concept drawing of the Model GTF-MD Series Gradient Furnace showing the relative positions of the monitoring thermocouples, the D-Tube hearth, and the sample on the D-tube hearth. Note the size and color differences from the hot end to the cold end of the monitored heating zone, which are indications of the effects of temperature.

End view of a hot Model GTF-MD Series furnace which shows the D-Tube hearth and monitoring thermocouples extending through the roof of the heating chamber tube.

An optional computer interface can be added to display and save the temperatures as a function of time during a multi-segment firing, as showed in the graph at the right. This is most helpful for studying the firing range of a ceramic body during a simulated production firing schedule. Make your mistakes and fine tune your production firing schedule in the lab, not in the production kiln !!!!

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