GemLab LED microscope - maxxiLED-2
Treatment   Untreated-treated rubies-sapphires for study, reference and research
  "The Heat Treatment of
Alchemy & Science"
by Ted Themelis
Articles   Read below interesting topics on gem treatments

Heat treatment technology
Heat treating ruby-sapphire
Beryllium detection with LIBS
Lead-filled rubies
Cranking up the heat
Treatment disclosure

A REMINDER "Forty years ago, I used to sell Ted's first microscope and other accessories. Before his death, R.T. Liddicoate saId Ted Themelis was one of the three individuals whose ideas pose the greatest threat to the GIA."" Dr.W.Hanneman

Gemlab Maxxi Muffle Furnace (Model M80N-1700, 1720)
Gemlab's Model M80N-1700 ("MAXXI MUFFLE"), all-in-one vertical muffle , bottom-loaded, furnace is the top of line with unparallel technology combined with superior longevity and incredible versatility designed by Ted Themelis for flawless performance.
The furnace is composed of four integrated modules: a) Power Module, b) Furnace Module, c) Temperature control Module, d) Atmosphere control Module.
The furnace is able to heat-treat one crucible filled with 3,380 cts of rubies-sapphires at any temperature to 1700oC (1720oC optional) in air, reducing, oxidizing, , with or without additives, or in vacuum at 1500oC, as desired by the user. The furnace may be used without muffle to increase loading capacity.
Features & specifications
Semi-floor model 400 (D) x480 (W) x 1100 (H) mm
Net weight is 128 kgs
Max. oper.temp. is 1700oC; 1720oC if 1850-grade elements
Loading capacity: Maximum 3.380 cts of corundum
Double steel shell design with dual air cooling fans (heating chambers and instrument cabinet)
Full atmosphere control for reducing-oxidizing
Vacuum pump with valve and vacuum gauge
Aluminum flange assembly for sealing the ceramic muffle
Alumina (99.9%) muffle tube, crucible, dishes
Molybdenum desilicide 1800-grade elements or 1850-grade for 1720oC operation (OPTIONAL)
Artificial intelligent temperature programmer/controller
Euroterm-brand SCR (Silicon Control Rectifier)
Long life Pt/Rh “B” type thermocouples (2 sets)
High energy fiber-board 1900-grade lining throughout
Analog and digital voltmeter, ammeter, on-off switch, key-switch, alarm-buzzer, hourmeter

Electric elevator control for loading-unloading crucible

Power: 2.2 KVA, plugs to any 220Vac 20A (1 phase)
Economical power consumption
Safe and easy operation
Long-lasting performance
Gas eIxhaust assembly
One year warranty on all electric, electronic parts

Model M80P-1700
immediate delivery from stock

Four integrated modules for Model M80P-1700, 1720

Power Module

Furnace Module

Temp. Control Module

Atmo. Control Module

Power isolated transformer
Elevator assembly with controls (Up, Down, Stop, speed control)
Incoming power voltmeter and ammeter shown the power consumption
Mains (208-230 VAC, 20A, 1 phase) and breaker circuit


1900-grade fiberboard insulation

Molybdenum disilicide 1800-grade heating elements

Port for muffle and elevator assemblies
Heating chamber octagon-shape
Dual fans with auto start-stop switch
Artificial intelligent single program main temperature programmer-controller with 51-segments and accuracy +/- 1oC plus 1 digit.
Artificial intelligent temp. limit controller accuracy +/- 1oC with single set al ram point shuts down the furnace in the event the main programmer temperature controller is failed
B-type thermocouple (2 sets)
SCR (Silicon Control Rectifier), controller and Trigger for power control management
Instrumentation: Hourmeter shown heating element consumption hours, start, stop emergency buttons, on-off switch, IN analog ammeter, voltmeter, OUT analog voltmeter, ammeter.
Dual One-way gas valves
Dual Pressure gas regulators
Dual Pressure gauges
Dual Gas mixer
Dual on-off valves
Dual 150 mm flow meters
Back pressure gauge
Hoses, brass inlet, exhaust port
Modes of loading and capacities for Model M80P-1700, 1720
  FURNACE CONFIGURATION. The heating process of the stones is performed using an alumina (99.96% purity) muffle tube, COE (Close-One-End), OD=80 mm, L=280mm mm, fastened hermetically and securely with metal flange assembly. In this mode, selected gases generated in the atmosphere control module can be purged directly to the muffle in "open-loop" mode, thus providing controllable atmosphere conditions with positive pressure up to maximum 1800oC temperature, or in vacuum -up to maximum 1500oC. The crucible is loaded in the chambers from the bottom using mechanical elevator and supported by special reticulated alumina post.
  SELECTIVE LOADING (6 DISHES). The unique feature of the M80P-1700 is the ability to load small quantities of ruby-sapphire in 6 alumina (99.6% purity) dishes which are inserted into the crucible and then in the muffle. Each dish is OD=69 mm, H=16 mm (each dish 153 cts, total 918 cts); the 6 dishes fit into one crucible OD=80mm H=100 mm. In this mode, stones from different localities, or stones with different features may be grouped and heated together on the same time, under the exact heating parameters without been mixed or contaminated each other. Likewise, fluxed and unfluxed stones may be placed in different dishes. Loading these stones in this method is particularly useful in research heating projects where contamination must be avoided and precision is required.
  BATCH LOADING FOR BULK PROCESS. To obtain maxium load capacity (3,3580 cts) rubies-sapphires may be loaded in one crucible and inserted into the ceramic muffle tube. This mode is suitable for heating corundum in the bulk with or without using additives under any atmosphere..
Glipses and features of Model M80N-1700, 1720
Measuring the skin temperature in Model M80N at 1700oC shows about 43oC well- below the industry standard of 65oC.
Measuring the temperature of the heating element and strap in Model M80N at 1700oC shows about 233oC, well- below the industry standard of 350oC.
The glowing loaded crucible is lowered from the heating chamber of the M80N-1700 furnace from 1700oC to 1250oC in less than 20 min., a feature that cannot be achieved by any other conventional engineering method. The crucible is resting on a ceramic module of advance reticulated alumina ceramic characterized by its very low mass and height melting point.
Standard equipment included in Model M80N -1700

Heating elements. One set (4 ps) of 1800-grade MoSi2 heating elements. Maximum element temperature in air is 1810oC. Furnace temperature is 1700oC

Temperature sensor. 2 pc. long life B-type thermocouples and thermo-couple extension assembly (2 pcs).

Flange: One set of metal flanges consisting of a 3-part assembly and 2 pcs O-rings for sealing hermetically the 80mm muffle ceramic tube at the bottom open end. Flange is equipped with water cooling passages and fittings - ready to accept any water-cooling system if needed.

Refractories (alumina 99.6% purity: 1 pc. reticulated alumina inserted in the muffle tube for holding the crucible above.

Technical ceramics (alumina 99.6% purity): 1 pc. crucible: OD=70 mm, L=95mm, V=309 cc net; load is ~3,380 cts of ruby-sapphire)
- 6 pcs dishes: OD=59 mm, H=16 mm, V= 153 cc net; load is ~321 cts of ruby-sapphire
Tube (muffle): 1 pc Close One End, OD=80 mm, L=280 mm

Main temperature programmer-controller: Single program, auto tune, 51-segment (steps), auto PID artificial intelligence temp. programmer-controller

Limit temperature: Single program, auto tune, single set point artificial intelligence temp. programmer-controller. Furnace is shut down automatically when the alarm temperature is reached.

Vacuum package: 1 pc pump (3.6 m3/h, 5 Pa, 150 W), 1 pc vacuum gauge, fittings and vacuum hose. The vacuum assembly is used in conjunction with the muffle tube.

Full atmosphere control. Includes the following: two 150 mm flow flow-tubes, two pressure gauges, two pcs on-off valves, two pcs one-way gas valves for purging directly into the muffle selected gas ( nitro, oxy), or any mixture of nitro-oxy, forming gas (hydro-nitro) for fully controllable atmosphere conditions to max.1700oC.
Gas Exhaust assembly: It consists of a glass jar, a backpressure gauge (0-3 psig), and fittings indicating that gas is exitng from the muffle port during gas purging.
Consumables and life expectancy of the parts


Electricity consumption depends on many factors. On a typical heating process the furnace requires less than1900 Watts to maintain 1700oC furnace soaking temperature for several hours.


A typical muffle tube lasts usually 12-15 runs if properly sealed at soaking furnace temperature about 1625oC in air; life expectancy is reduced proportionally as the furnace temperature is increased; 8-10 runs in vacuum at 1500oC for 2 hours
The life expectancy of technical ceramics (crucibles, disk, dish) depends on many factors (heating up rate, cooling down rate, soaking temperature, time are soaking temperature, type of fluxes and other additives is used. Technical ceramics usually last 10-12 runs at soaking 1700oC for several hours.
B-type thermocouple assembly lasts over 200 runs at 1700oC furnace temperature.


The life expectancy of the heating elements depends on many factors which should be carefully considered.; Best performance and longivity is heating between 1200oC to 1720oC (air, oxygen, other gases), max.1500oC (vacuum) No guarantee is given by any heating element manufacturer around the world on element brakeage. However, experience shows that more than 20 heating runs may be performed at 1700oC soaking time 10-70 hours/run before an element breaks or damaged. Generally, the estimated life expectancy for each element is about 1,500-1600 hours. If an element breaks is should be replaced without requiring to change all the other elements in the furnace.


Comparison features between all Gemlab models, setting up heat-treatment facility and consumable required
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