Numerous laboratory and industrial processes use solvents to separate substances and samples from each other. The ability to reclaim both the solvent and sample is important for both the bottom line and the environment. Rotary vacuum evaporators employ rotational speeds of up to 280rpm with vacuum conditions of < 1 mm Hg to vaporize, condense, and ultimately distill solvents. Rotary evaporators can accommodate samples sizes of up to 1 litre. A rotary evaporator is commonly vertically-oriented to save bench-top space, and utilizes efficient flask or vapor tube ejection systems to expedite the process. Vacuum seals, typically made of graphite and polytetraflouroethylene (PTFE), and stop mechanisms provide long-term and reliable safety guarantees. A rotary vacuum evaporator also provides time-lapse control.

What is a Rotary Evaporator?

Cannabis extraction equipment:Theory of rotary evaporator

A Rotary Evaporator is used  for the purpose of separating solvents such as Ethanol from cannabis, and produce refined oil using regulated temperatures and precision.  This is where you become the extraction artist, by understanding your cannabis and knowing how it will react under specific conditions.  Two main components rotary rvaporator are going to be the flask, which spins in a Heated Bath, raising the temperature of your substrate in the loading flask and vaporizes the solvent, allowing it to be drawn towards the coils; this is the second main piece of the puzzle.

Two other important pieces are the vacuum pump, drawing the vapor towards the coils and reducing the boiling point of the substance you’ve loaded, which ranges, but most popular is Ethanol.  The other is the “Chiller”, the necessary tool to cool the fluid running through the condenser, reverting your distilled chemicals from a vapor into a liquid.

Cannabis extraction equipment:Applying rotary evaporator to Cannabis Distillation

Distillation can be explained as a process that involves turning something into a vapor by heat, carrying that vapor elsewhere, and condensing it back into a liquid.  So here you have it, your first step into professional cannabis refinement; we know you’re going to be at the top of your game and the artist you were born to be!

The water bath accommodates flasks up to 5L for a scaled-up, but still gentle and controlled heating of your extract. As your extract is heated, solvents evaporate and condense in either a dry ice or a chiller-cooled coiled condenser where they can be collected and reused for future extractions. Distillation rate can be modulated by controlling the rotation and bath temperature (Hei-VAP Precision model offers vacuum control for total automation). All Heidolph products carry a 3 year warranty.

Theory of rotary evaporator

  1. Temperature of the Heating Bath: The higher the temperature of the bath, the faster your product will boil at a given pressure. The boiling temperature of your product is determined by the pressure of the system. A higher water bath temperature will not raise the temperature of your product above boiling, but it will put in energy faster. In standard distillation, the pressure is kept constant and the temperature of the product slowly rises with time as more and more product boils off; the rate of distillation is determined by heat input. In a rotovap, the temperature of the heat input (and, roughly, the temperature of the product) is kept constant and the distillation is adjusted by controlling the pressure.
  1. Pressure of the Distillation: The lower the pressure, the lower the boiling point of your product and the faster you will distill at a given bath temperature (i.e., at a given heat input).
  1. Speed of Rotation and Size of the Flask: Generally, the larger the flask and the higher its RPM, the quicker the evaporating process (there is more new surface area exposed per unit time).
  1. Size and Power of the System: The speed of distillation in a given system is limited primarily by the condenser’s ability to condense the solvent vapor (it is rare to be limited by the heater). If you allow too much vapor to rush into the condenser, it will overload and be unable to work efficiently, which will result in a loss of valuable volatiles. According to the manufacturer Buchi, to avoid saturation, you should monitor the pressure of the system such that 2/3 of the condenser is consistently covered with condensate. If liquid begins to form on the top 1/3 of the coil, the incoming vapor runs the risk of being sucked out into the vacuum pump and being lost forever. In practice we often let the condensation get closer to 3/4 of the way up the condenser. Another indicator is the “condensation line,” usually above the area where you see actual liquid on the coils. This is easy to see in water distillations, but hard to see in alcohol distillations. Here is a good one:

Unfortunately, it takes a while to become comfortable adjusting the pressure. Until then, your “get out of jail free card” is the “air button.” A quick push of this button will raise the system pressure, clearing the condenser and allowing you to start afresh.

The speed of distillation is important because the faster you distill without saturating, the better the flavor. This is a fact.

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