Author Topic: A Microwave of good use...  (Read 2101 times)

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  • Guest
A Microwave of good use...
« on: June 19, 2003, 07:28:00 AM »
Recently there has been a lot of controversy, especially in the stimulants forum, about the efficacy of using a microwave for various procedures of clandestine synthesis.  Here is a microwave I have found that should take away many of the problems associated with most commercially available microwaves.  They can be found extensively at auctions of companies that go bankrupt.  A product like this can go for a very attractive price. 

I just wanted to inform the bees that like to use microwaves for other purposes than popping corn that there are better options available than what your local department store has to offer 8)   

The use of microwave technology as a means of achieving rapid fixation, dehydration and staining of biological tissue has been investigated extensively in recent years. It has been proven that microwave processing accelerates diffusion, can stabilize proteins, and can speed up chemical linkage. The problem in establishing routine laboratory procedures using microwave technology has been the inadequacy of kitchen microwave ovens. The (deleted)Microwave Processor solves this problem. It is a sophisticated piece of scientific equipment with which reproducible conditions can finally be applied to microwave processing, and which incorporates critical safety features. This latest model has been designed by (deleted) to include a stainless steel microwave cavity and a more efficient microwave stirrer.

The features of the Microwave Processor include:

Temperature control within +/-1/2° C(by way of submergable heat sensor.)
Attainment of temperature even with non-polar media such as paraffin and xylene
Air bubble agitation
Safety-interlocked extraction system to vent fumes from organic solvents at a rate of 100 cfm
2-second cycle time
Dual-range digital countdown timer, programmable in hours and minutes or minutes and seconds, accurate to 1 second
The accurate temperature control achieved by the(deleted) ensures reproducible results.lets say you want to heat a solvent for 4min at 67C you just punch in 4:00 and 67 and when the temperature reaches 67C it will start counting down 4min) Using microwave processing techniques with the (deleted)Microwave technology also dramatically reduces the amount of expensive reagents needed.

Microwave histoprocessing is a simple, 3-step procedure (100% ethyl alcohol, isopropanol, paraffin) that can take as little as 25 minutes (for needle biopsies). In electron microscopy, microwave processing has been successfully employed in aldehyde fixation, epoxy embedding and osmium staining, and has been demonstrated to improve penetration in many colloidal gold labeling techniques. The (deleted)will continue to fundamentally improve the speed and reproducibility of routine tissue processing procedures currently employed by microscopists.

Typical applications:
Clandestine Chemistry
Microwave-stimulated fixation
Microwave histoprocessing with paraffin
Antigen retrieval
Special Stains
Electron microscopy fixation and embedding
Immunogold labeling
DNA in situ hybridization
DNA amplification
Ordering Information:
Microwave Processor, 110V
Microwave Processor, 220V
Note: 220V Microwave Processor is not available with a carousel .

Multiple Air Bubble Agitator (reduces bumping)

Made in the U.S.A. (Sorry Osmium)
1 year warranty on parts and labor
Certified compliance with all applicable FCC and EC standards
Output Power: 1,000 watts
Dimensions (including vent): 20¼" H x 21¾" W x 23½" D
Chamber dimensions: 9" H x 13¼ " W x 15½" D
Weight: 85 lbs
Related Products and Information:
Microwave Ovens and Accessories
Procedures and Technical Information


  • Guest
A lousy modified household micro
« Reply #1 on: June 21, 2003, 06:57:00 PM »
Nothing what a garage sale micro can´t do also.

There is much better stuff available if you want to spend money. Some essentials for a professional device:
- monomode/multimode switching
- includes pressurizable containers
- possibility to use standard glassware setups (distillation etc.)
- doesn´t look like a cranky household micro out of a wet Osmium dream.

Modifying a household microwave better as the described one in the post before is quite easy if one has some knowledge on electrics/electronics. This enablea to solve the biggest problem - the power regulation. (modify by rewiring voltage doubler circuit to full wave rectifier without voltage doubling. Install own power supply for filament heating. Now the MOT can be connected to a dimmer - all other parts MUST STAY on regular energy source, fan etc. Other way: Scavenge and regulate power by varying load in the cavity.)
Not for the technical impaired but also no rocketscience.

The next place in this thread is reserved for the standard: "no metal in the micro" message posted by someone who has no clue but wants to say something nevertheless.

Of course microwaves are the devils and your soul is lost if doing such modifications. Be warned!


Patent US5387397

might be an inspiration for the heroes from brotherhood of the multimeter.  ;D
The next stage would be as described in

Patent US5689008



  • Guest
Microwave Leuckart
« Reply #2 on: June 22, 2003, 12:16:00 AM »
Whilst on the topic of microwaves, has anyone ever had any luck with a "monomode conversion"?

And, has anyone had anyone had any luck with the fabled "microwave Leuckart"?

P.M. me if you like. ;)


  • Guest
« Reply #3 on: June 22, 2003, 08:25:00 AM »
The by me outlined modification by disabling the voltage doubler for full wave rectification gives monomode output.  ;)  So yes - I did several monomode conversions. (if you want the full power output there is another circuit necessary with six diodes and two capacitors. But 1000Watt is to much)

But no Leuckard was ever tried by me up to now. sorry.


  • Guest
more --'er that's M.O.R.E.
« Reply #4 on: June 22, 2003, 04:00:00 PM »
the power supply of all the MO i have had the pleasure to scavenge is pretty simple and straight forward.  there's a high voltage filtration capacitor and a high voltage diode to ground to rectifiy the secondary of the transformer.

the digital timers are neat stuff and work independently from the rest of the hv portions.

I do not totally understand the variable portion of the controlling circuit but assume it is some type of pulse width or duration switch. that is cycling the hv on and off to obtain an average power level less than maximum. that wasn't very clear was it?

anywho there's some patent stuff somewhere on this aspect.

getting too much power is the deal from what I understand. and therefore a cyclic controller is desirable. means average power is less than otherwise.

I gotta learn to communicate verbally--- some day.


  • Guest
ehem, Jimwig one moment please...
« Reply #5 on: June 22, 2003, 09:18:00 PM »
Sorry to tell, but your understanding of the function of microwaves is - eh, yes, it is somehow - let´s say "incomplete"?  ::)

The capacitor filters nothing but stores the energy of one halfwave.
This is not straight forward but a quite tricky voltage doubling circuit (tip: the magnetron is the second diode!)
The power is switched on and off thats all - like at 50 percent there is 5 seconds full power and 5 seconds nuthing, at 25 percent, 2,5 seconds full power and 7,5 seconds nothing.....
This is whats to overcome or whats to get better controlled. It depends on the application, the kind of reaction.....

I really like the last sentence of your post.  :)  
What does it say?


  • Guest
voltage doubler - like with diodes and caps...
« Reply #6 on: June 29, 2003, 02:45:00 PM »
voltage doubler - like with diodes and caps hooked into a "staircase" affair as with Marx generators. Yes i was curious as to why the diode seemed to be grounded to case but did not have time to explore polarity etc. the inner working of the thyratron are indeed unknown territory. thanks for the info. i must try to get a handle on lethal items more  closely.


  • Guest
screw the microwave
« Reply #7 on: July 02, 2003, 01:24:00 PM »
i would have to agree with 2much, microwaves cause uneven heating due to the differences in density and composition of anything they are heating, (test it by heating mashed potatoes with gravy and steak, see that some items overcook while others are still cold or have cold spots). also it can be hard to see clearly into them to observe.  i would stick with simpler and more reliable methods. also, a microwave is a small comfined space that can quickly fill with gas (possibly explosive gas) in an environment of electronics and electrical equipment-see spark,BOOM.  also, any corrosive gas/vapor can degrade or corrode electronics and cause various problems


  • Guest
Fucking Christ
« Reply #8 on: July 02, 2003, 04:15:00 PM »
If you would have read the original fucking post, I was giving a simple alternative to the conventional microwave, for folks that can not modify their own microwave. The microwave I posted eliminates, hot spots and superheating by way of surface tension agitation, and built up gasses by an internal exhaust fan.  I should have known that the fuckers that are using microwaves for clandestine purposes are fucking idiots anyway, I was just trying to help.  And the microwave I posted takes away many of the problems that most folks have with microwaves available on the retail markets.
     I should have never started this thread, I do not personally use microwaves, I just wanted to show bees that there are other products available that are superior to the kitchen micro everyone owns.  Sorry!

EDIT:  Wow I did not mean to bee such a bitch, I am not sure what caused me to blow up like that.  I think I am not very tolerant when I start a modafanil rotation. :(


  • Guest
cool, calm and collected.....
« Reply #9 on: July 02, 2003, 06:25:00 PM »
dear MethylEthyl is how to go here. (or you will have to endure deep frustration - or even worse, you become like them!)
irfoxxx1 - congrats. You failed in simple brownnosing. Thats hard. Real hard.

The mixture was stirred under nitrogen at different temperatures: 140, 160 and 170°C, in a Multi-mode Microwave Reactor “no source” - Figure 2 (microwave frequency - 2,45GHz, maximum of microwave power - 300W), for time required to obtain epoxy numbers about 0,11. 
Normally 40% of full microwave’s power was used. Every 5 minutes a small sample of epoxy resin was taken from the mixture to determine the epoxy number. After the reaction the epoxy resin was cooled down and powdered. 

No source Microwave Reactor implements novell Concentrated Microwave Field (CMF) which provides the microwave field focused onto the reaction vessel. 
The temperature can be measured at the bottom of the reaction chamber using Infra-red thermometry with fine beam focusing.

The quote is taken from an online available article named:
"Synthesis of high molecular weight epoxy resins under microwave irradiation"

The used microwave reactor has
- more features (whats not so important, on-off and power regulation are already to much for most chemists)
- costs approximated one-third of the one shown in the first post. (this is important!)

The manufacturer has more sophisticated, pressurizable reactors available - also low cost but full featured. For the interested who has to go by the price sure worth a look.
For those not interested/fearing microwaves a good news: Since last month those who don´t want to are allowed to work without microwaves!  Isn´t this great folks?

(The last sentence was a joke btw.)

Regarding the hundreds of millions of microwave ovens sold and the astonishing small rate of accidents also the devices are home-used what says abused as abused can be it is to state that microwave ovens are very safe. Period.

And great for chemistry after my opinion. I wouldn´t eat something what was cooked in a micro - but thats another story.


  • Guest
who's brownnosing?
« Reply #10 on: July 03, 2003, 05:34:00 AM »
The reason i failed at brownnosing was that i wasnt trying to, i was simply trying to help the people who may read the info about the microwave in question, and decide to simply use a household one, with possible dissasterous results, or may to modify one without having any clue what they are doing.  i made no mention of there being anything wrong in any way with the one disscussed by methyl. it appears to solve all of the issues i mentioned. damn, relax people, no one is talking shit about your mothers, we're talking about chemistry, dont take it so personal. also, if trying to inform and help others or simply posting an opinion is brownnosing, then all of the hive must be guilty, because that is the nature of the forums, unless im mistaken.


  • Guest
I apologize, jrfoxxx1.
« Reply #11 on: July 03, 2003, 04:07:00 PM »
The "brownnosing" wasn´t appropriate and unnecessary at all. Thanks for replying in a civilized way - this makes it easy to lay the conflict down before it really starts.

But Payin2Much was actually promoting the use of microwaves for the safety which is given by the very stable cavity. And you are as a matter of fact wrong on the point that the cavity may explode - this is near to impossible - the fan blowing through the cavity hinders this and even if a gas/air mixture would explode this would do not to much harm - the door will break open and release the pressure. The microwave construction engineers have been aware that they will not be able to hinder the normal user to boil alcohol and other stuff in a microwave oven - actually to boil everything what can boil. So the cavities are constructed to withstand such a "worst case scenario" without killing the owner or hurting him badly. They did good work on this - I know this from experiance. (and reading up on it later).

Payin2Much tells in his post why he prefers a solvent fire in a micro over a solvent fire on a kitchen stove and I agree with him on this. Microwaves can - if used with a little common sense - provide additional security. Payin2Much told also the main point in operating  such a device in a safe way: Whatever happens, shut down power and LET THE FUCKING DOOR CLOSED! DON`T LOOK - WAIT! After five minutes nothing to happen you may take a first look from distance through the window. (thats to calm down curiosity). Wait half an hour longer before opening the door. (I say half an hour in the hope to ensure ten minutes of waiting at least).
The hard part is to do nothing, to wait also you may see or smell the fire in the micro. But this is easy regarding whats up if you have a solvent fire of equal dimensions on the stove/hotplate.

ragNAroeKK !


  • Guest
your right
« Reply #12 on: July 04, 2003, 09:29:00 AM »
Thank you too for also responding in a civil manner, and, upon review, you are correct. i did misunderstand part of payin2much's post a bit somehow. he is advocating it as a safer alternative, which it may be, in the majority of cases, but i still feel that that one in a million scenario where part of a microwave may become shrapnel or become fuel for a solvent/electrical fire is a bit of a steep risk for something i feel would be a poor heat source anyway.  However i will conceede that properly thought out, using homogenous materials so heating is even and using common sense like not using it to boil gasoline,naptha, ether etc it could be a safe or evensafer alternative, but i still dont know that it is a more effective or conveniant way of heating than a hotplate (kind of hard to see whats going on in a microwave most times, could be very easy to overheat).


  • Guest
Modification of a commercial microwave oven
« Reply #13 on: August 29, 2003, 11:01:00 AM »
Rev. Sci. Inst., 1993, 64(2), 529-31


Modification of a commercial microwave oven for applications in the chemical laboratory

M. A. B. Pougnet
Department of Chemistry, University of Cape Town, Rondebosch, 7700, Republic of South Africa
(Received 11 September 1992; accepted for publication 5 October 1992)

A commercial microwave oven has been modified for laboratory applications. The modifications include the lining of the cavity with polypropylene, the use of a polypropylene turntable, incorporation of inlet and outlet ports, and the use of an extraction system to purge the oven’s cavity.


After a long history of microwave processing in industry and the use of microwave ovens in the home, the first report on a chemical laboratory application using microwaves appeared in 1974, when a microwave oven was used to dry small samples.’ This was followed by a publication concerning microwave sample dissolution using mineral acids (digestion).’ Since then the number of reports on laboratory sample preparation and other uses, such as for organic and organometallic synthesis, has grown tremendously. j-7 Earlier work was carried out in commercial ovens designed for kitchen use with few or no modifications and several shortcomings were apparent. This led to many investigations into the development of suitable equipment to carry out the chemistry safely and efficiently. The first commercial microwave moisture analyzer oven became available in 1981 and an oven for sample digestion in 1985. Today there are several manufacturers of laboratory ovens. Specially designed microwave transparent pressure vessels for sample digestion are also available from several suppliers. The cost of these laboratory ovens is relatively high and many laboratories are using domestic ovens. Perhaps the most important problem in using these in laboratories is the high degree of corrosion when using mineral acids that can lead to malfunction of the units, excessive microwave leakages, and electrical fires. Furthermore, when working with volatile organic solvents, vapors can be sucked back in the power supply compartment where the occurrence of a spark could also lead to a dangerous situation. In this report, the modifications to a commercial microwave oven to make it safe for laboratory applications are described.


After investigating the suitability of several available microwave ovens for the modification, the SHARP model R-lOR50 INVERTER oven was chosen. This oven was selected for the following characteristics: robust construction and stainless steel cavity; relatively large cavity size to accommodate the lining (see below) and a wide variety of available pressure vessels; efficient cooling of the magnetrons and adequate overheat protection; easy programming of several heating steps (power/time); and the excellent power control that is available through the use of two 500-W magnetrons (total available power of 1 kW) and a state-of-the-art INVERTER circuit that allows power levels to be adjusted in 10% increments. The desired power is set in watts and is continuous at the different levels as compared to pulsed operation of the magnetron in most ovens. In this system, only one of the magnetrons is used for power settings of less than 500 W and the power delivered by this magnetron is controlled by the inverter circuit. For larger power settings, the latter is controlled and the second magnetron operates at full power. The output power calibration of the oven is shown in Fig. 1. Excellent linear and reproducible calibration is obtained for 1- and 2-l water loads. The advantage of this system for laboratory applications, where small loads are normally used, is that lower power levels can be used which minimizes the amount of reflected power reaching the magnetrons. Results obtained for the heating of small volumes of water at different power levels is shown in Fig. 2. A dummy load of 100 ml of water was placed in the cavity during the tests and the positions of the test loads were kept as constant as possible. The apparent absorption of power for the different loads (reproducible to within a few percent) illustrates the “antenna” effect that is related to the shape and size of the object in relation to the electromagnetic field in the cavity. Adequate heating rates are achieved for small loads of water, mineral acids of relatively low boiling points, and polar organic solvents. Because of small volumes of solvents normally used in laboratory applications, a dummy load ( - 100 ml water) is
normally included. The latter is not found to affect the reproducibility of heating of the samples.


The oven as purchased is fitted with grill, convection, and rotisserie facilities. These components were removed and their electrical connections terminated. The cavity lamp was removed. The standard turntable motor was replaced with a stronger geared motor capable of turning a load of 8 kg at 5 rpm. To accommodate the larger motor, the legs of the oven were raised by 10 cm. A polypropylene lining (10 mm thick) was fitted inside the cavity with an indented section to allow the normal flow of air from the cooling of the magnetrons to the air outlet section (Fig. 3). The front of the lining was sealed to the cavity with silicone compound and the stainless steel front of the cavity was treated with several layers of PTFE coatings (Nr.438, A. W. Chersterton Co., USA).

FIG. 1. Output power calibration.

FIG. 2. (a) Temperature increase for 20-s irradiation of water loads.
(b) Calculated power absorbed for 20-s irradiation of water loads at 300 W.

FIG. 3. Polypropylene lining of the cavity. The mounting of the gas tube in front of the air inlet port is visible at the back of the cavity.

Two stainless-steel ports (41.3 mm i.d., 130 mm long) were fitted to the cavity (visible in Fig. 4) by bolted double flanges. One at the back of the cavity serves as an air inlet and one on the lhs as the outlet. The ports are lined with polypropylene and provide a completely plastic connection between the lining and the extraction system (see below). This design was used to offer a free-flow system, thus preventing changes of the velocity and avoiding condensation, as often occurs with perforated ports. A filter is fitted to the air inlet port. The extraction system is connected to the outlet port through a flexible 32-mm PVC hose. The extraction system comprises a high-speed fan and operates by a venturi effect (Fig. 5). Thus no corrosive fumes can reach the motor/fan. This system provides a high extraction rate of greater than five cavity volume changes per minute and is completely demountable for cleaning. The outlet of the extraction system is routed outside the laboratory or to a laboratory fume hood.

FIG. 4. Inlet port and filter at the back of the oven and the outlet port connected to the extraction system. The small port is also visible on the side of the oven.

FIG. 5. The extraction system. The venturi nozzle section can be disconnected from the larger tube containing the electric motor for cleaning.

A small stainless steel port (15.8 mm i.d., 80 mm long) lined with polypropylene was fitted for using fiber optic temperature measurement devices, pressure lines, for flushing gases through the cavity, or for special extraction purposes. The standard turntable was replaced by a 15-mm thick polypropylene one fitted with wheels. This turns on the polypropylene bottom of the cavity lining. The mass of the relatively heavy pressure vessels therefore does not rest on the gearbox of the motor. The standard lamp was ineffective through the thick polypropylene lining. A small fluorescent lamp as is used for caravan lighting ( 130 mm long) was used instead. Direct ionization of the gas in the lamp is achieved even at low powers. The problem of using such tubes is that they get very hot, especially at the metal caps, and cracking of the glass occurs. This problem was dealt with by inserting the two ends of the tube in stainless-steel tubes and exposing only about 30 mm of the tube’s center portion and placing this in front of the inlet port where the flow of air keeps the tube cool. This device is simple and offers a bright light and can be inserted when visual observation is required.
By means of current sensing circuitry in the extraction fan motor and a relay placed in the oven’s power input line, the operation of the oven is not possible without proper functioning of the extraction system. This precaution was deemed necessary for complete protection in laboratory applications.


The modified oven was tested for microwave leakages. Levels were below the 1 mW/cm’ specified by legislation for new equipment ( < 5 mW/cm2 in use). The polypropylene lining structure showed slight deformation after several weeks of intensive use, but the basic shape and function was not affected. The extraction system was found to provide sufficient flow to deal with acid fumes released from venting valves of pressure vessels and boiling off of organics. No condensation was noted within the cavity or in the extraction system. The system has been successfully installed in our laboratory for over a year and has been used extensively for sample digestion using a wide range of pressure vessels and mineral acids, for drying of samples, and for reactivation of silica gel and molecular sieve containing organic solvents.

Research grants from the University of Cape Town and the Foundation for Research and Development (FRD) are greatly appreciated. The author thanks A. I. Chalef, K. Achleitner, and D. W. M. Lensen for their technical inputs.
1. J. A. Hesek and R. C. Wilson, Anal. Chem. 46, 1160 (1974).
2. Abu-Samra, J. S. Morris, and S. R. Koirtyohann, Anal. Chem. 47, 1475 (1975).
3. H. M. Kingston and L. B. Jassie, Introduction to Microwave Sample Preparation, Theory and Practice, ACS Professional Reference Book, Washington ( 1988).
4. H. Matusiewicz and R. E. Sturgeon, Prog. Analyt. Spectrosc. 12, 21 (1989).
5. MM. A. B. Pougnet, ChemSA 284 (1989).
6. R. Gedye, F. Smith, and K. Westaway, J. Microwave Power Electromagnet. Energy 26, 4 (1991).
7. D. M. P. Mingos and D. R. Baghurst, Chem. Sot. Rev. 20, 1 (1991).