Freeze Drying

Vacuum concentration and freeze drying are related methods used for the gentle drying or preservation of thermally sensitive materials. This often involves the removal of aqueous media. As can be seen from the state diagram of water, which can also serve as an example for other solvents, above a certain process pressure (in this case 6.1 hPa for H2O) drying occurs from the liquid phase. At pressures below this level, the water temperature drops below 0 °C.

Drying occurs directly from the frozen state, bypassing the liquid phase. The triple point (in this case p = 6.1 hPa and T = 0 °C for H2O) can be regarded as a sort of boundary between vacuum concentration (or drying) and freeze drying. Ice, water and vapour can be observed simultaneously in the chamber. The key features of the two methods are listed in the following table.


Vacuum Concentration

Freeze Drying

Evaporation Temperature Range

- 5C to- + 20C

- 60C to 0C


Usually dissolved; residue is a powder or a crystalline substance

Solids (including ceramics, meat, archaeological objects, bones, plants and books)


Various solvent types (some exotic)

Aqueous solutions, only small quantities or special solvents

Water / Solvent Content

Approx. 5% final context

Low residual moisture possible (<1%)

Process Time

Minutes to hours

0.5 - 3 days; Several weeks in some case

Christ systems also allow the two methods to be combined in a Rotational Vacuum Concentrator (RVC). Starting at a relatively high pressure (e.g. 20 hPa) and then reducing it to a lower pressure (e.g. 1 hPa) concentrates an aqueous DNA solution to a small residual volume, which then freezes in the device at the lower pressure. Final drying occurs by sublimation.

Product concentration by sedimentation at the bottom of the test tube is a desirable side effect.
This means that Rotational Vacuum Concentration (RVC) not only protects the specimen against superheating but also prevents diffuse product distribution in the test tube, which can lead to low recovery rates.

SP Scientific is the synergistic collection of VirTis and Hull freeze dryers.

VirTis is one of the most established freeze dryer manufacturers in the world.  The company is focused on understanding the freeze drying needs of researchers everywhere and dedicated to providing top-quality equipment with superior application and technical support.

BenchTop Pro small

The VirTis BenchTop Pro freeze dryers have been designed to meet the needs of the most demanding research laboratories. Each system can be configured to meet your present and future needs. Condenser refrigeration packages of -55°C, -75°C, -85°C and -105°C can meet the demands of both aqueous or aqueous-solvent based formulations.

Key Features:

  • Compact, bench-top design
  • Available in 3, 8 and 9 liter configurations
  • Direct chamber, flask and/or rack drying capabilities
  • PLC-based Omnitronics™ controller
  • Choice of refrigeration system to meet various process requirements
  • Optional manifolds, racks and accessories available

The AdVantage provides a small benchtop freeze dryer for scientists who require both manifold and tray-type freeze drying. Shelf temperatures as low as -55C and condenser temperatures to -85C supports a wide range of applications. The one-shelf Advantage is available in bulk or stoppering, with aluminum alloy cast shelf and an internal condenser.

Key Benefits:


  • Compact, bench-top design
  • Easy scale up from the AdVantage Plus to larger pilot scale freeze dryers
  • Clear acrylic door for easy product viewing during processing
  • Stoppering or bulk configurations
  • On-board Wizard controller
  • Manifold and tray type drying in a single unit
  • Easy install, requires standard laboratory utilities
  • Accommodate a wide array of products with shelf temperatures to -55C and condensers to -85C

The Genesis Pilot Lyophilizer is constructed with versatility in mind so that this freeze dryer can meet any lyophilization requirement. Shelf temperatures as low as -70C and condenser temperatures to -85C supports a wide range of applications. Available in bulk or stoppering configurations and with up to 6 shelves. Each system is available with a selection of control formats and temperature and vacuum sensors. The Genesis allows you to configure a freeze dryer to meet your own particular application requirements.

Key Features:


  • Compact, freestanding mobile design
  • Easy scale up from the Genesis to full production
  • Choice of control strategies/systems
  • Precise vacuum level control
  • Ability to backfill with inert gas
  • Clean room configurations available
  • Easy defrost condenser with quick turnaround time
  • Front-facing vacuum pump allows easy monitoring and maintenance
  • 316 SS shelf design with optional stoppering ram
  • Configure the system to meet your needs. Choice of refrigeration, control and shelf and condenser configurations allows for simple to complex systems custom configured to meet your particular needs.
  • Accommodate a wide array of products with shelf temperatures to -70C and condensers to -85C

The LyoStar3 is designed to meet the needs of R&D professionals. Our freeze drying equipment is used for applications ranging from process development for scale-up to product processing for stability studies to formulations work. Models are available in stoppering and bulk configurations.  The LyoStar is an R&D and process development freeze-dryer that provides unmatched process accuracy, reliability and unique ease-of-use features. The LyoStar features Type T thermocouple-controlled shelf temperature accuracy of +/- 0.5°C or better and vacuum control within 0.1% of set-point. Its robust 5.5 hp cascade refrigeration system enables shelf pull down from ambient to –40°C in less than 25 minutes, and the ultra-reliable scroll compressors feature just 3 moving parts.  LyoStar3 is available with Praxair ControLyo™ Nucleation on Demand Technology.

LyoStar3 Key Features:

  • SMART Freeze-Dryer Technology helps automate and shorten the development of freeze-drying cycles
  • Delivers product information that has previously been unavailable during a cycle – dried layer resistance, heat flow and mass transfer
  • Designed to facilitate scale up bu maximizing features in comon with well-designed commercial systems
  • Configured with superior instrumentation for complete process information – isolation valve, capacitance manometers, Pirani gauge, 16 thermocouples, Allen Bradley PLC
  • Available with 21 CFR Part 11 compliant software and full validation packages

View this demonstration of our ControLyo™ technology:


Hull and VirTis offer cGMP vacuum freeze drying equipment for the reliable lyophilization of a wide range of pharmaceutical and biotech products. We have a broad line of standard freeze dryer models and ancilliary equipment such as Clean-in-Place, Steam-in-Place and autoloading and unloading systems. We also provide highly customized equipment upon request, utilizing fifty-plus years of industry experience and in-house engineering and fabrication resources.


Scitek has market leading expertise in freeze drying technology. Together with our partners Virtis and Hull our experts can customise to suit virtually every application.