• Complete laboratory grade, vacuum bell jar system
  • Contain a fine vacuum to less than 0.1 Torr (100 millitorr)
  • Glass bell jar, vacuum pump plate and gasket
  • Dial gauge to monitor vacuum pressure in bell jar 
  • Fine needle valve to regulate vacuum pressure
  • Shutoff valve to vacuum pump
  • Use for  lab & industrial applications and science education experiments
  • Economical alternative to vacuum oven

The vacuum bell jar system, model GVAC3, consists of a  glass vacuum bell jar on a vacuum pump plate with built-in Bourdon Dial Vacuum Gauge and Vacuum Bleed Valve Regulator. A rubber gasket provides the seal between bell jar and vacuum plate.  The assembly creates a vacuum chamber with a volume of 2.6 L (0.7 gal).  

The vacuum bell jar system is capable of a dynamic vacuum of 29.92 in. Hg or better (<0.1 Torr) using a two-stage 1 CFM rotary vane pump; pump-down time to reach 0.1 Torr (100 millitorr) is 3 minutes or less.  Every model GVAC3 is tested to this pump-down time specification.

The high vacuum bell jar is made of molded, thick walled, annealed flint glass.  The thick glass walls handle the pressure differential between atmospheric pressure and fine vacuum inside bell jar. Flint glass* offers all round visibility of material inside bell jar. The internal dimensions of the bell jar are 8.75 in. (22.2 cm) height to top inside radius and 5 in. (12.7 cm) ID diameter (refer to photo with dimensions). Volume of bell jar is 2.6 Liter (0.7 gal).  Ground glass base flange creates vacuum tight seal to gasket on vacuum plate. Molded knob on jar top for easy handling.

Vacuum pump plate (8 x 8 in.) is made of durable, thick, chemically resistant HDPE (high-density polyethylene). Included with the vacuum plate is a gum rubber gasket.   As vacuum pump removes air from bell jar, normal air pressure pushes the bell jar against the vacuum pump plate.  Normal air pressure is a standard atmosphere corresponding to 14.7 lbs per square inch. The gasket between the bell jar and plate creates the vacuum tight seal without needing messy, sticky vacuum grease.

The Oil-free Bourdon dial vacuum gauge provides a quick and easy way to measure vacuum pressure in the bell jar and a controlled environment.  Vacuum pressure is any pressure below atmospheric pressure.  The gauge displays the vacuum pressure in the bell jar from 0 in. Hg(atmospheric pressure) to 29.92 in. Hg(0.01% of atmosphere). One in. Hg corresponds to approximately 25 Torr.

A vacuum bleed valve regulator is built-into the vacuum plate for monitoring and regulating vacuum level.  This regulator consists of a  fine brass needle valve and a 2 in. OD Bourdon dial vacuum gauge, 0 to 30 in. Hg.  

By opening and closing the fine needle valve,  user can adjust flow of air into vacuum pump and vary vacuum pressure in bell jar or maintain a consistent level.  The Bleed Valve Regulator allows user to maintain specific vacuum pressure in bell jar.  Vacuum control allows user to regulate vacuum level in vacuum chamber.  Needle valve acts as a vent valve and provides a gentle vacuum release at the end of an experiment. Gentle vacuum release protects the sample from air inrush when vacuum chamber brought up to atmospheric pressure.


Three benefits of bleed valve vacuum regulator with vacuum gauge include:
  1. Monitor vacuum level in bell jar when running process
  2. Repeat vacuum pressure in bell jar to generate reproducible experimental results.
  3. Run controlled atmosphere experiment by backfilling gas into the bell jar chamber through #10-32 female threaded port on needle valve (refer to photo of vacuum pump plate)
Additional features of Model GVAC3 include:
An on/off chrome-plated brass vacuum ball valve on the plate is shutoff valve to vacuum pump and is used to isolate vacuum chamber from vacuum pump. The brass hose barb on ball valve accepts 3/8 in. (10mm) ID flexible vacuum tubing.

The vacuum pump plate has four rubber bumper feet.  For durability, the feet are held in place with bolts threaded into the plate.  The feet raise the vacuum plate off the surface and provide cushioning and stability to the plate.



Common applications of Model GVAC3 Vacuum Bell Jar System
  1. Gentle vacuum drying of thermal, oxygen, and/or moisture-sensitive materials.
  2. Vacuum drying and outgassing electronic and medical parts.
  3. Remove air bubbles in epoxies, silicones and other viscous materials
  4. Protecting oxygen or water sensitive samples
  5. Demonstrate science education experiments


Science Education Experiments
  1. Demonstrate in real-time Boyle's law by showing how the volume of a balloon changes as vacuum pressure in bell jar is varied. 
  2. Show sound needs a medium to transmit as the sound from a bell or buzzer fades as vacuum pressure decreases and sound returns as it is increased. Note at what vacuum pressure (29.7+ in. Hg) the sound source fades completely and becomes inaudible. 
  3. Explain why water can be made to boil at room temperature. Note the boiling occurs when the vacuum pressure matches the vapor pressure of water (≈29 in. Hg) at room temperature (25°C).  Raise vacuum pressure slightly and watch the boiling abruptly stop.
  4. Demo fluid transfer under low vacuum pressure from sealed flask thru U-shaped tube to a beaker in bell jar. Raise pressure in bell jar and watch as fluid flows back to sealed flask.
  5. Illustrate how the tiny air sacs (tiny balloons) making up a marshmallow, peep, or shaving cream inflate according to Boyle's law as vacuum pressure decreases. Note the vacuum pressure when the air sacs break causing the marshmallow, peep or shaving cream to deflate. 


Comparison of GVAC3 vacuum bell jar system and vacuum oven:

A glass vacuum bell jar with vacuum pump plate is an economical alternative to a vacuum oven for fast and efficient vacuum drying of heat-sensitive, easily oxidized or fragile samples. Both glass bell jar vacuum systems and vacuum ovens use a vacuum pump to reduce the pressure within a sealed chamber.  Both use vacuum gauges to monitor vacuum pressure, come with shut-off valves to isolate vacuum chamber, include a vent valve and use a gasket to provide vacuum seal. Both are leak tight to reach dynamic fine vacuum levels, less than 0.1 Torr.  Both dry samples by lowering the vacuum pressure below the boiling point of the solvent(s) or gases adhering to or dissolved in the sample.  The vacuum pump removes these evolved solvent vapors and gases from sample. Common applications for glass vacuum bell jar systems and vacuum ovens include drying electronics and medical components, curing epoxy coatings,  degassing liquids, desiccating, and protecting oxygen or water sensitive samples. 

* Molded flint glass may show small imperfections. These imperfections, tiny spheres or surface blemishes, form during molding process and do not impact use in full vacuum applications.