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 Model HPLT-200 High Pressure - Low Temperature "Oiling" Apparatus

Gemlab's High Pressure-Low Temperature model HPLT-100 gemstone oiling machine is a desktop, compact apparatus that works in any environment. The oiling apparatus is used to induce oils, resins, oleoresins and almost any combination of compatible liquid "fillers" of any viscosity into the surface-reaching fissures on emeralds and other gemstones. This results in "filling" the cracks/fissures of the gemstone hiding their imperfections, increasing their diaphaneity, thus producing apparent clarity improvement. The practical application of the oiling is based on simple principles in physics enabling to obtain pressures to 260 bar ( 3770 psi) at 120oC in about 45 minutes depending the type of filler, load and other parameters. Higher pressures to about 600 bar (8700 psi) are achieved if the temperature is increased to 200oC. In this model vacuum package is included as standard equipment for total flexibility. The oiling apparatus consists of these parts:
-Stainless steel capsule - where the stones are loaded, heated and highly pressurized
-Pressure gauge (range 0-600 bar (7,977 psi), ON-OFF valve and other fittings
-Control console housing the temperature programmer/controller, various other temperature control parts and instruments

-Vacuum package includes high quliaty 2-stage vaccum pump with solenoid valve, vacuum gauge, vacuum hose, etc.

Gemlab's Oiling apparatus Model HPLT-200

Features & specifications
Desk-top, measures 280 (D) x 280 (W) x 100 (H) mm
Net weight is only 9 kgs
Recommneded operating temperature range from 25oC to 100oC
Maximum pressure is 600 bar (8700 psi)
Loading capacity per run: 880 carats of beryls (full load)
Heavy duty stainless-steel capsule and all other parts
Heavy duty vacuum pump package
Drain port for removing oil from the capsule; cooling fan
Fastening tool for tighten the cover of the capsule
Single program, auto-tune, 30-step, artificial intelligent temperature programmer/controller that controls indirectly the desired pressure
Internal band-type heater (500W @ 220 Vac)
SSR temperature control method
Long-life “K- type" thermocouple
Analog ammeter, on-off power switch, alarm-buzzer, key-switch, fuses

Power: 500 W, plugs to any 220 Vac 3A (1 phase)

Very low power consumption, only 250 watts needed to maintain pressure at 260 psi (3800 psi)
Safe and easy operation
Long-lasting performance
Usually in stock; FOB Bangkok; check for availability
One year warranty on all electric and electronic parts

Controllable pressures to 260 bar (3800 psi) can be achieved in 45 minutes

One canister, perforated at the bottom, can hold maximum of about 880 carats of mix-size and mix-shape beryls for oiling.

Outside (skin) temperature of the capsule cover measures below 50oC


75oC <-> 100 bar-1450 psi
80oC <-> 130 bar (1885 psi)
85oc <-> 150 bar (2175 psi)
90oC <-> 200 bar (2900 psi)
95oC <-> 230 bar (3336 psi)
120oC <> 260 bar (3771psi)
150oC <> 300 bar (4351psi)
NOTE: Above temperature and pressure values may varied depending on the load, type and amount of the filler oil in the capsule, and other process parameters.

Why the programmer-temperature controller is used in model HPLT-200?
This feature is provided in Model HPLT-100 for these reasons:
-Allows to set the precise temperature, thus the operating pressure is precisely set by the operator to desired value
- Prevents the oil-filler turning yellowish-brownish by setting the temperature below the known flash point of the filler
-Allows 30 different ramps and dwells during the oiling process. Example: The pressure can be raised to a desired value at any heat-up rate; then, soak at any given time; then, raised or decreased to any temperature set point, and so on. This heating profile accelerates the filling into the surface-reaching fractures of the stone by repeated changes in the viscosity of the filler which promotes capillary action.
Artificial Intelligence (AI) temperature programmer-controller is standard part in all models of the Oiling machines fabricated by GEMLAB.

Why vacuum is not used in model HPLT-200?

Since early 1980's Ted has conducted many experiments to determine the practical use of the vacuum in the oiling process. It was concluded that for most bulk processing applications, no significant benefit of the vacuum use was noted. For routine processing application the use of the controllable pressurized capsule like model HPHT-100 is satisfactory.

Ted in 1992 with his HPLT vacuum-pressure gem oiling apparatus
How about the trapped air-gas in the capsule of the HPLT-200 oiling machine?
Most of the trapped air/gas in the capsule exits by opening slightly the control on-off valve of the capsule while the system is operated at temperatures below 70oC (varied depending of process parameters) with very little pressure. It is a very simple technique which can be constantly improve by the operator.
Trapped air/gas exiting from the capsule and it is clearly visible through the tube exit port.
How long takes an oiling process using the HPLT-200?
It all depends on the type of fractures in the gemstones, the type of filler and on heating profile (temperature-pressure, ramp rates, etc; the shortest time in a typical oiling process of emeralds is about 2-3 hours; for other types of oiling processes can take weeks, if desired.

Retrieving the stones after the process

1. What is the oiling process in gemstones?
The oiling is a process aiming to reduce the visibility of surface-reaching cracks, crevices, fissures and other dislocation features in the gemstone; thus, the treatment upgrades its clarity, improves its overall appearance, and increases its value.

The preferred emerald filler

Joben - most used emerald filler in India, but it contains green-colored dye

Balsam oil used in Colombia, USA and elsewhere for oiling different types of gems

"Opticon" - most commonly used filler in the trade

Hair tonic oil used in Thailand for oiling Burmese rubies

"Araldrit GY 250" used mainly in Colombia for oiling emeralds

2. Which type of gemstones are suitable for oiling?
Many porous and non-porous gems may be oiled: Commonly emerald and other beryls, frequently diamonds, occasionally rubies, sapphires; other gemstones (opal, turquoise, rhodochrosite, etc.), are also oiled.
3. Which quality of the gemstone are oiled?
All qualities of emeralds and other gemstones are subject to the oiling treatment as long as the stone has surface-reaching fractures..
4. Are only cut and polished gemstones subject to oiling process?
Rough, as well as cut and polished gemstones, may be oiled in various ways.
5. How significant is clarity the improvement in the oiled gemstones.
The clarity improvement vary from minor (sometimes no improvement) to significant; various clarity grades have been introduced by several gemological laboratories, but they are highly subjective and not universally agreed.
6. Is the oiling process in gemstones permanent?
The oiling treatment is not permanent, because all the fillers used in the process are not stable. In most cases the oil is leaked out from the gemstone leaving behind filler residues. In this cases the gemstone should be "re-oiled".
7. Is the oiling process in gemstones reversible?
.The oiing process is conditionally reversible. Depending the filler used, there will always be some residue left behind; the filler may be removed using various cleaning methods without harming the gem; however, if hardener is combined with the filler may be very difficult t be removed.
8. If the oiling treatment detectable?
In most cases the oiling treatment in rough or cut is detectable regardless of the oiling method or filler used in the process.
9. Are oiled emeralds and other oiled gemstones may change appearance (or even damaged) under normal "wear-and-tear"?

Since the filler used in the oiling process is not stable, the gemstone eventually will be "damaged" affecting its appearance and value. Damaged gemstones due to oiling may be submitted to specializing lab for "re-oiling" to restore its previous appearance. General precautions to extend the life expectancy of the filler are: Avoid steam cleaning, high heat during jewelry repairs, exposure to direct sunlight, strong household solvents, ultrasonic; also avoid using hard toothbrushes and strong solutions for cleaning.

10. Are the Gemstone Reports ("certs") issued by gemological labs stating "no oiling" in their "cert" assure that the gemstone is not oiled?
Often, non-oiled emeralds and other gemstones are submitted by some gem dealers to a commercial gemological lab receiving "no oil" status in the Gemstone Report. Thereafter, these gemstones are oiled and sold with the same Gemstone Report stating "no oil'. It is a well-known scam.
11. What is the "ideal" oil to be used in oiling process?
Here is the specs for the "perfect oil filler" - which does not exist in the market:.
SUBSTANCE: Natural organic
COLOR: Ideally colorless
DISPERSION: Should be low
REFRACTIVE INDEX: Most desirable is nD=1.56
DENSITY: Not critical; it may range between 0.90 to 1.00 gr/cc
FLUORESCENCE: Inert, or very slightly faint fluorescence under LW or SW.
VISCOSITY: The viscosity of the oil may be high at 25oC, as much as 2,000 cSt.; when the oil is heated to some temperature (to be determined according to its flash point) then its viscosity should be decreased dramatically (below 100 cSt -the lower the better). At cooling to 25oC its viscosity should be increased back to 2,000 cSt (with tolerance 10%).
SOLUBILITY: The filler should be insoluble in water; it may be slightly soluble in alcohol, ethers, etc.
STABILITY: Should be relatively stable, non-volatile, and non-drying upon exposure in normal lighting conditions.
ODOR/TASTE: Should be odorless, tasteless.
12. What type of "oil" can be used in the oiling process of emeralds and other gemstones?

Oils: Cedar wood oil, paraffin oil, clove oil, cinnamon oil, oil combos, other
Resins: Various types of resins
Oleoresins: Canada balsam (others classified as resin)
Synthetic epoxy resins: "Opticon" (or Resin 224)
Polymers: Various combinations of polymers
"Palma oil" a synthetic resin (known as Araldit 6010, Resin 828, or Epon 828) and it is not recommended because it turns whitish in few months;. "Gematrat & ExCel") is used extensively in the USA, Colombia and elsewhere, "Permasafe" and other fillers are also used..

13. Which is the best available natural oil used in oiling process?

Colorless Cedar wood oil is regarded as the best available oil in the market today. It is accepted in the international gemstone market. However, cedar wood oil is often mixed with other natural or synthetic substances.

14. Are dyes can be used in combination with the fillers?
Suitable dye may be mixed with compatible oil-filler and be used in the oiling process. Most notable the "Joben" as standard practice of oiling emeralds in India.
15. What are typical pressure required for oiling emeralds?
Typical pressure for oiling Zambian emeralds is about 3500 psi, increased pressure may expand their fractures and can break apart
16. Are the oiling treatment equipment complicated?
Oiling methods and equipment vary from simple (dipping the stone into some oil and retrieve it overnight) to High Pressure - Low Temperature sophisticated electro-mechanical apparatus such as the Gemlab model HPLT-100..
Beryl before (up) and after (down) oiled with Mazzola oil! Note the large fissure (lower left side) is not readily visible
Rhodochrosite before (left) and after (right) treated with Opticon
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