sublimation comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying; lyophilisation; cryodesiccation | Regional spelling and historical terms. |
| Primary drying pressure | 0.05-0.5 mbar (5-50 Pa) | Kept below the triple point of water; product-specific. |
| Shelf temperature range | -40 to +40 °C | Freezing, primary, and secondary stages use different set points. |
| Cycle duration | 12-72 hours | Depends on fill volume, formulation, and equipment. |
| Condenser temperature | -50 to -80 °C | Must remain below the product's ice temperature. |
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
The four substrates of this enzyme are phenylacetone, reduced nicotinamide adenine dinucleotide phosphate (NADPH), oxygen, and a proton. Its products are benzyl acetate, oxidised NADP+, and water. This enzyme is a flavoprotein of Baeyer-Villiger monooxygenase type, which uses molecular oxygen as oxidant and incorporates one of its atoms into the starting material. The systematic name of this enzyme class is phenylacetone,NADPH:oxygen oxidoreductase. This enzyme is also called PAMO.
=== DVD documentary === A DVD documentary is a documentary film of indeterminate length that has been produced with the sole intent of releasing it for direct sale to the public on DVD, which is different from a documentary being made and released first on television or on a cinema screen (a.k.a. theatrical release) and subsequently on DVD for public consumption. This form of documentary release is becoming more popular and accepted as costs and difficulty with finding TV or theatrical release slots increases. It is also commonly used for more "specialist" documentaries, which might not interest a wider TV audience. Examples are military, cultural arts, transport, sports, animals, etc.
Several major Big Boy franchisees accepted Marriott's offer and became Roy Rogers regional franchisees, including Abdow's, Frisch's, Elias Brothers, Marc's, and Shoney's which together covered much of the Northeastern, Midwest and Southern US. Pittsburgh franchisee Eat'n Park rejected the offer and took public offense at paying fees to Rogers. In the Pittsburgh area and elsewhere, other regional franchisees were sought who would also subfranchise to smaller operators, and by January 1969, Marriott claimed regional franchises for every state but Alaska. Roy Rogers' restaurants also opened in Canada, franchised to that nation's Big Boy franchisee, JB's of Canada. Marriott divided the United States into 33 franchise regions and required regional franchisees open a set number of restaurants in a four-year period. Regional franchisees would pay Marriott a 2% royalty, and subfranchisees typically pay the regional franchisee 3%, who would keep the additional 1%. A restaurant required a $35,000 cash investment upfront, including $7,500 paid to Marriott. Additionally, the cost of the building and equipment, with seating for 42 persons, cost about $100,000 in 1968, excluding the cost of land. Marriott offered financing but charged an interest rate of 12% on land and 17% for the building. The prototype restaurant seated 40 to 45 persons with additional outdoor seating on an optional patio in front of the building, but actual restaurants varied, one franchisee's dining area accommodating 75 persons.
Sources: en.wikipedia.org
=== Lotion === Lotions are similar to solution but are thicker and tend to be more emollient in nature than the solution. They are usually oil mixed with water, and more often than not have less alcohol than solution. Lotions can be drying if they contain a high amount of alcohol.
Aquaphor is a brand of over-the-counter (OTC) skin care ointments manufactured by Beiersdorf Inc., an affiliate of Beiersdorf AG. The brand was introduced in the United States in 1925. In accordance with the Food and Drug Administration's OTC Skin Protectant Monograph, Aquaphor contains 41 percent petrolatum (petroleum jelly) as its active ingredient. It is used to temporarily protect minor cuts, scrapes, and burns, as well as chapped or cracked skin. The product line includes ointments for compounding, general skin therapy, lip repair, and baby care. Aquaphor is used and recommended by health care professionals for minor post-operative wounds or defects.
Jim Reid – vocals, guitar, bass, synthesizers (1983–1999, 2007–present) William Reid – guitar, bass, vocals, synthesizers (1983–1999, 2007–present) Mark Crozer – rhythm guitar (2007–2008, 2012), bass (2013–present), backing vocals (2007–2008, 2012–present) Scott Von Ryper – guitar, backing vocals (2015–present) Justin Welch – drums (2021–present) Former members
Sources: en.wikipedia.org
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.
Reduced pressure lowers the boiling point of water and allows ice to sublime at temperatures below freezing. It also helps remove water vapor from the product toward the condenser. The exact pressure is chosen to stay below the triple point of water.
No. Materials with low solids content or high volatile solvents may form weak or collapsed cakes. Some proteins and cells require stabilizers to survive freezing and drying stresses. Feasibility depends on formulation and process design.
Primary drying removes ice by sublimation under vacuum. Secondary drying removes water that is bound to the material, often by warming the product after most ice has left. Both stages occur below temperatures that would cause unwanted melting.