DENTON BENCH TOP TURBO

CARBON EVAPORATOR / GLOW DISCHARGE

Two Pump System (Mechanical & Turbo)

   

Materials: Denton Bench Top Turbo Carbon Evaporator, lead carbon rods, white paper pieces approx. 1” x 1”, paper tape, sunglasses, Pioloform coated grids.

   

Procedure for Carbon Evaporation onto coated slot or mesh grids:

 

1.      Open the bell jar by raising it up.  Then set the bell jar on the highest holder.

 

2.      Prepare to load a pair of carbon rods, one after the other, into the C-shaped holder set, referred to as holder set #2. Note that one rod has both ends flattened. Use some sandpaper, if necessary, to really flatten the ends of this rod. Note that the other rod of the pair must have one pointy end. It is this fine point that emits the fine carbon dust.

 

a)      First, load the pointy rod, flat end first, through the outside end of the left or “fixed” arm of the holder. Then load the flat rod the same way. The flat rod will, in turn, continue to push the other rod right into the right arm. This right arm is spring-loaded.

b)      Use a 1/16” wooden stick to continue to push the flat rod in order to extend it about 3/8” out the other side of the left arm. Then tighten the screw located above the left arm.

c)      Next, pull back the right or spring-loaded arm of the holder and extend the pointy rod 3/8” out towards the flat rod. Then tighten the screw located above the right holder. The pointy end should now be abutting against the flat rod with the force of the spring-loaded arm. See diagram:

 

d)        If necessary, adjust the height of the holders to control the amount of carbon to be evaporated. The higher the holders, the less carbon “dust” will be dispersed and visa versa. To judge if the height is appropriate, as well as the duration of the evaporation session, then it is necessary to “test coat” a white piece of paper before actually coating any grids.

 

3.      To “test coat” a small piece of white paper, tape the paper from its underside to the rotating stage platform.

 

4.      Make sure that the round wand of the glow discharge apparatus is not touching the holders.

 

 

5.      Prepare to close the bell jar. First, run your finger around the underside of the black gasket and the opposing surface of the base plate to remove any dust, debris or excess grease. You may have to re-grease the gasket with Apiezon grease if it is excessively dried out.

 

6.      Then lower the bell jar in place.

 

7.      Turn on the main power switch, located on the right side of machine.

 

8.      See front panel lights go on! Then press the PUMP button located on the left upper front panel, under CONTROL area.

 

9.      This activates the mechanical pump, which starts evacuating the bell jar. Try to lift the jar. It should be difficult as the air is being drawn out. If it is easy to lift, then suspect a problem. In that case, turn off PUMP by depressing PUMP button. Turn off the main power switch. Lift bell jar and check if any dirt, hair, or excess grease is preventing a good seal. Then lower the bell jar and turn on main power, then press the PUMP button. Hopefully, the bell jar will evacuate.

 

10.   It will take up to 2 to 6 minutes for the vacuum to reach an appropriate level. At about 350 mTorr, the TURBO PUMP is activated. This is indicated by the red light coming on the left side CONTROL area under the label TURBO. In addition, the red light under the ACCEL label comes on (located on the right panel PROGRAM/GAUGE).

 

11.  Soon, the red NORMAL light (located on the right panel) will come on when the vacuum reaches about 5.2E –6 Torr. Now conditions are ready for carbon coating or glow discharge!

 

12.  Depress the ROTATION button (left panel). Then turn the ROTATION POWER dial (right panel) to adjust the speed of the rotating stage. Rotating the stage allows for an even dispersal of the carbon onto coated grids. Rotation is optional.

 

13.  Proceed to initiate carbon evaporation.  To do this, then depress the FILAMENT # 2 button  (left side panel).

 

14.  Then slowly, turn the FILAMENT POWER dial clockwise  (on the lower right panel), until the filament current reaches 20 to 24 amps. See these values displayed on the panel. Simultaneously, note that the pointy carbon rod changes from glowing red to glowing white. View the rods with sunglasses on for a brief period only, as it is extremely bright!

 

15.  As soon as the rods start to “spark”, reduce the filament current by 5% by turning the FILAMENT POWER dial slightly counterclockwise. At this stage, the carbon is being dispersed as a dust onto the white test paper. Actually, the carbon is said to “sublime”  (changes from a solid to a gas with no liquid intermediate phase). 

 

16.   When enough carbon has covered the test paper, i.e., light to medium gray color, then turn the FILAMENT POWER dial completely counterclockwise and depress the FILAMENT # 2 button, to stop the process. Usually, a light gray color indicating a light layer of carbon is sufficient to coat Pioloform or Formvar grids.

 

17.  Press the PUMP button to turn off the vacuum pump and allow air into the bell jar (venting).

 

18.  After the bell jar is completely vented, then lift up the bell jar and remove your test paper. Repeat the test on a new piece of paper if the carbon thickness is not satisfactory. Increase or decrease the duration of carbon evaporation to control carbon thickness. Also, you can raise or lower the holder.

 

19.   The carbon rods and the holder will be very hot to the touch. Wait several minutes for them to cool before removing the spent rods.

 

20.  Replace with a set of new rods.

 

21.  If you are ready to coat any filmed grids, then position the glass microscope slide, containing filmed grids, on the rotating stage. Tape the slide, from its underside, onto the rotating stage, if needed.  

 

22.   It’s a good idea to place a small piece of new test paper somewhere on the slide, away from the grids. The test paper will indicate the level of carbon dispersed.

 

23.  Close the bell jar.

 

24.  Press the PUMP button to activate vacuum pumping sequence.

 

25.  Again, wait until the proper level of vacuum is reached and the TURBO and ACCEL red lights are lit.  Next, the NORMAL red light will be lit up.

 

26.  You can choose to rotate and or tilt the stage during carbon coating, at this point.

 

27.   Press the FILAMENT # 2 button.

 

28.  While wearing the sunglasses, slowly turn up the filament current (clock-wise via FILAMENT POWER dial) to 20 to 24 amps until some sparking is detected (rod point should be glowing white). Then lower the current by 5%.

 

29.  Stop the carbon dispersion as soon as enough carbon is seen on the white test paper by turning FILAMENT POWER dial counter-clockwise. Then depress the FILAMENT # 2 button to the off mode.

 

30.  Depress the PUMP button to vent bell jar.

 

31.  When bell jar completely vented, then lift up jar and remove grids. This set of grids should be successfully carbon coated according to desired thickness.

 

32.  One can go on to carbon coat more grids or stop or choose to glow discharge the grids immediately after carbon coating them. Or one can glow discharge the carbon coated grids at some later date. The glow discharge process renders the carbon grids more hydrophilic and allows easier pick up of floating Epon sections during microtomy. If you wish to carbon coat another set of grids, remove old carbon rods and replace with a new pair. Change the rods for each batch of grids.

 

33.  If you choose to stop, then remove the old carbon rods.

 

34.  Then, clean the interior of the bell jar by swabbing it with 100% methanol and allowing it to air dry. Then close the bell jar. Turn off main power.

 

35.  If on the other hand, you choose to continue to carbon coat more grids, then follow the procedures outlined above.

 

36.  If on the other hand, you decide to glow discharge the grids immediately after carbon coating, then proceed to the following steps:

 

37.  GLOW DISCHARGING AFTER CARBON COATING: After turning off filament power and depressing FILAMENT #2 to off mode, then press the GAS button to the on mode (on left panel).

 

38.  Now wait for 3 to 5 minutes or so as the Turbo pump completely shuts down and air is vented into the bell jar to a certain level, i.e., between 70 to 100mTorr.  If this level is not attainable, then adjust the air-inlet valve, which is the black knob atop the machine.

 

39.  Turning this black knob counterclockwise opens the valve and lets air into the bell jar.  Turning this knob clockwise closes off the valve and holds the air inside at a certain pressure/level, e.g., 70 to 100mTorr. 

 

40.  Once reaching 70 to 100mTorr, then press the GLOW button (left panel). The encircling wand will glow, “purple”. Allow this purple discharge to remain on for the next 1 to 2 minutes to “clean” your grids.

 

41.  Depress the GLOW button again to turn off discharge.

 

42.  Depress the GAS button.

 

43.  Depress the PUMP button to vent the bell jar.

 

44.   Lift bell jar and remove grids. The hydrophilic state of the grids lasts only several days. After that, the grids seem to become more hydrophobic again. They can be glow-discharge rejuvenated at a later date, if needed. Store the grids in a dust-free container, e.g., plastic Petri dish.

 

45.  If you opt to glow discharge on another day, follow steps # 5 through 11.  Then, after the NORMAL ready light comes on, turn on the GAS button. Then wait 3 to 5 minutes for the vacuum to read 70 to 100mTorr.

 

46.  Then press the GLOW button to activate the wand to discharge to a purple color.  Allow 1 to 2 minutes of discharge to clean grids.

 

47.  When finished, depress the GLOW button. Then depress the GAS button, and then depress the PUMP button to vent bell jar.

 

48.  Just as an option, argon gas can be substituted for “Air”, see manual.

 

 

MAINTENANCE:

 

At the end of each carbon coating session, while bell jar is raised on upper holder, then it can be cleaned. Swab out interior with towel paper moistened with 100% methanol. Allow jar to air dry, and then lower it onto base plate for storage.

 

If it really gets too black, then clean with an abrasive, like Comet or Ajax cleanser. Then rinse the bell jar extremely well, with water-dampened paper towels. Then wipe with 100% methanol-dampened paper towels and allow jar to dry. Then lower it to base plate.

 

Additional maintenance: Keep the vertical rod (on which the bell jar is raised and lowered) lubricated with WD-40.

 

Use high vacuum grease, e.g., Apiezon L, (Ladd Research Industries, Inc., Burlington, Vt.) to grease the 10” diameter bell jar gasket periodically.

 

Run the Denton Bench Top Turbo at least once a month, if it is not being used regularly to keep up its overall functioning.

 

Check the level of the rotary mechanical pump oil periodically. To see the gauge, open up back hinged panel of machine. The mechanical rotary pump is located on lower right side. The normal level of oil should cover the red “bull’s eye”. See diagram:

For service on the Denton Bench Top Turbo, contact the following individuals:

 

 

Mr. Richard Daniel                       1-201-847-8845

                                                       Cherry Hill, New Jersey

 

Mr. Jim Falco                               1-856-439-9100

                                                      Morristown, New Jersey

 

 

For parts, contact:          Also refer to manual for part #’s

 

Ida Kelly (or Sandi)                  1-856-439-9100

               FAX #                        1-856-439-9111

 

                                                  Denton Vacuum

                                                  1259 North Church Street

                                                  Morristown, New Jersey 08057

 

 

 

 

 

 

To change the black rubber gasket on the bell jar:

 

Procedure:

 

1.      Firstly, prepare to remove the cage covering the bell jar. Use a hexagonal wrench to remove the five clamping screws connecting the cage to the metal “belly band”. Place these screws aside.  Lift the cage up and set it on the raised holder for now.

 

2.      Carefully, pick up the bell jar and invert it. Then place it in a small wastebasket, which will serve as a support.  

 

3        Observe how the bellyband is attached to the bell jar. Make a mental picture of how the bolt and nut assembly looks to make it easier to re-assemble it later. Then remove the bellyband by unscrewing the assembly. Place the band aside for now.

 

4.      Remove the old electrical tape holding the rubber gasket to the bell jar.

Discard this tape.

 

5.      Observe how the old rubber gasket sits on the bell jar, closely fitted. Then

Remove the old gasket. Discard this gasket for recycling if appropriate.

 

6.      If the bell jar could use a cleaning at this time, proceed to do so. It is easier

To clean it while it is lying in the fume hood. First, clean the exterior edge of the bell jar with 100% acetone to remove any adhesive from the old tape and any grease. If the interior is heavily carbon coated, scrub with some wet paper towels containing Comet cleanser or baking soda. To rinse all the cleanser off, carefully place the inverted bell jar in a sink that is lined with paper towels. Then run 2X-distilled water into the bell jar.  Pour out the water. Then wipe it clean with more paper towels. Then run more running water into the bell jar to really rinse it well. Repeat this sequence several times. Then wipe the interior and exterior dry with paper towels. Return the jar to the fume hood.

 

7.      Rinse the interior of the bell jar with 100% ethanol. Then pour out any excess ethanol. Allow bell jar to air dry.

 

8.      Prepare to attach the new rubber gasket to bell jar. Place the bell jar back into the wastebasket or prop it up on a supported area of a counter. Or have someone hold it while you are trying to put the new gasket on. Position the gasket over the edge of the bell jar and stretch it to fit. Ensure that the gasket is well seated.

 

9.      Seal the gasket to the glass bell jar with a double application of electrical tape. Allow only a ¼” of tape to extend against the glass bell jar. Most of the tape should be on the rubber gasket.

 

10.  Prepare to re-attach the bellyband to the bell jar. Invert the bell jar in the wastebasket or have someone hold it. Next, position the bellyband on the glass, directly adjacent to the gasket. Then attach the bolt/nut assembly. Ensure that the positions of the five clamping screw holes in the bellyband do not sit over any electrical tape. Tighten the bolt/nut assembly.

 

11.  Place the bell jar back onto the Denton Vacuum stage. Position the bell jar so that the bolt/nut assembly of the bellyband will be oriented to the cage opening, as originally set up.

 

12.  Lower the cage onto the bell jar. Adjust the bell jar to coincide with the notch/opening of the cage, accordingly.

 

13.  Re-attach all five of the clamping screws but do not tighten them completely.

 

14.  Lift the bell jar up again and apply some Apiezon grease to the new rubber gasket lip.

 

15.  Clean the base plate of any dust or debris.

 

16.  Lower the bell jar.

 

17.  Turn on the main power to Denton Vacuum. Then depress the PUMP button to activate the pumping sequence.

 

18.  Once the highest vacuum level is achieved, then tighten all five clamping screws.

 

19.  Then depress the PUMP button to vent the bell jar.

 

20.  When bell jar is completely vented, then turn off main power.

 

21.  That’s it!

 

 

 

                To change the mechanical pump oil:

 

              New mechanical pump oil is a golden color. When it starts to change color to reddish brown, as seen in the gauge, then it is time to change it.

 

1.      Run the Denton Vacuum about 20 minutes to warm up and thin out the existing mechanical pump oil.

 

2.      Then turn off the Denton Vacuum and unplug the machine.

 

3.      Open up the back hinged door to the Denton Vacuum.

 

4.      Remove the filter to the mechanical pump. This filter can be replaced at the same time.

 

5.      Place a tray or cup under the spigot of the pump to catch any oil. Then open up the spigot to drain the pump.

 

6.      Close the spigot once all or most of the oil is removed.

 

7.      Pour in new pump oil via the filter opening. Fill the pump until the oil level is just above the red “bull’s eye” in the gauge. Leave a small air bubble atop the bull’s eye.

 

8.      Then replace the pump with a new filter.

 

9.      Close the back of the Denton Vacuum.

 

10.  That’s it!