Anti-fog
Encyclopedia
Anti-fog agents, also known as anti-fogging agents and treatments, are chemicals which prevent the condensation
of water
in the form of small droplets on a surface which resemble fog
. Anti-fog treatments were first developed by NASA
during Project Gemini
, and are now often used on transparent glass
or plastic
surfaces used in optical applications, such as the lenses
and mirrors found in glasses
, goggles
, camera lenses
, and binoculars
. Anti-fog treatments work by minimizing surface tension
, resulting in a non-scatter
ing film
of water
instead of single droplets, an effect called wetting
. Anti-fog treatments usually work either by application of a surfactant
film, or by creating a hydrophilic surface.
during the Project Gemini
, for use on helmet visor
s. During Gemini 9A
, in June 1966, Astronaut Eugene A. Cernan tested NASA's first space suit
, and discovered during the space walk that his helmet visor fogged, among other issues. Cernan's suit was tested using the Spacecraft 9 life support system after the flight, when it was discovered that a small patch of the visor treated with an anti-fog solution remained clear of condensation
. Later Gemini flights all included the anti-fog solution, for application prior to the space walk occurring.
solution
s, cream
s and gel
s, and wet wipe
s, while more resistant coating
s are often applied during complex manufacturing
processes. Anti-fog additives can also be added to plastics where they exude from the inside to the surface.
, but this method is criticized because detergents are designed to be water soluble and they cause smearing. Divers often use saliva, which is a commonly known and effective anti-fogging agent. Other home recipes exist, including the application of white vinegar with hot water, or a mixture containing sudsy ammonia
, alcohol
and liquid dishwasher detergent .
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
in the form of small droplets on a surface which resemble fog
Fog
Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...
. Anti-fog treatments were first developed by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
during Project Gemini
Project Gemini
Project Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966....
, and are now often used on transparent glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
or plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
surfaces used in optical applications, such as the lenses
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
and mirrors found in glasses
Glasses
Glasses, also known as eyeglasses , spectacles or simply specs , are frames bearing lenses worn in front of the eyes. They are normally used for vision correction or eye protection. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or...
, goggles
Goggles
Goggles or safety glasses are forms of protective eyewear that usually enclose or protect the area surrounding the eye in order to prevent particulates, water or chemicals from striking the eyes. They are used in chemistry laboratories and in woodworking. They are often used in snow sports as well,...
, camera lenses
Photographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...
, and binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
. Anti-fog treatments work by minimizing surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
, resulting in a non-scatter
Scatter
In ordinary English, to scatter is to distribute randomly. Scatter also has the following meanings:*In physics, scattering is the study of collisions, especially of waves and particles...
ing film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
instead of single droplets, an effect called wetting
Wetting
Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting is determined by a force balance between adhesive and cohesive forces.Wetting is important in the bonding or adherence of...
. Anti-fog treatments usually work either by application of a surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
film, or by creating a hydrophilic surface.
Development
Anti-fog agents were initially developed by NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
during the Project Gemini
Project Gemini
Project Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966....
, for use on helmet visor
Visor
A visor is a surface that protects the eyes, such as shading them from the sun or other bright light or protecting them from objects....
s. During Gemini 9A
Gemini 9A
- Backup crew :- Original primary crew :- Mission parameters :* Mass: * Perigee: * Apogee: * Inclination: 28.91°* Period: 88.78 min- 1st rendezvous :* June 3, 1966 - 17:45 - 18:00 UTC- Spacewalk :* Cernan...
, in June 1966, Astronaut Eugene A. Cernan tested NASA's first space suit
Space suit
A space suit is a garment worn to keep an astronaut alive in the harsh environment of outer space. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, and are necessary for extra-vehicular activity , work done outside spacecraft...
, and discovered during the space walk that his helmet visor fogged, among other issues. Cernan's suit was tested using the Spacecraft 9 life support system after the flight, when it was discovered that a small patch of the visor treated with an anti-fog solution remained clear of condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
. Later Gemini flights all included the anti-fog solution, for application prior to the space walk occurring.
Application
Anti-fog agents are usually available as spraySpray
Spray can refer to:* Spray ** Aerosol spray** Blood spray** Road/tire spray, kicked up from a vehicle tire** Snow spray, a spray that creates artificial snow fall...
solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
s, cream
Cream (pharmaceutical)
A cream is a topical preparation usually for application to the skin. Creams for application to mucus membranes such as those of the rectum or vagina are also used. Creams may be considered pharmaceutical products as even cosmetic creams are based on techniques developed by pharmacy and...
s and gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...
s, and wet wipe
Wet wipe
A wet wipe, also known as a wet nap, wet towel, or a moist towelette, is a small moistened piece of paper or cloth that often comes folded and individually wrapped for convenience...
s, while more resistant coating
Coating
Coating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...
s are often applied during complex manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
processes. Anti-fog additives can also be added to plastics where they exude from the inside to the surface.
Agents
The following substances are used as anti-fog agents:- SurfactantSurfactantSurfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s that minimize the surface tension of the water:- DetergentDetergentA detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
s, including shampooShampooShampoo is a hair care product used for the removal of oils, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair...
and soapSoapIn chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
, applied as a solution and wiped off without rinsing
- Detergent
- Shaving creamShaving creamShaving cream is a substance that is applied to the face or wherever else hair grows, to provide lubrication and avoid razor burn during shaving. Shaving cream is often bought in a spray can, but can also be purchased in tubs or tubes. Shaving cream in a can is commonly dispensed as a foam or a gel...
applied and wiped off without rinsing. - Hydrophilic coatings that maximize the surface energySurface energySurface energy quantifies the disruption of intermolecular bonds that occur when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically favorable than the bulk of a material, otherwise there would be a driving force for surfaces to be created, removing...
:- Hydrophilic polymerPolymerA polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s and hydrogels:- GelatinGelatinGelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...
- Gelatin
- Hydrophilic colloidColloidA colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
s and nanoparticleNanoparticleIn nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s:- Titanium dioxideTitanium dioxideTitanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
, becomes highly hydrophilic under UV lightUltravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
.
- Titanium dioxide
- Hydrophilic polymer
Home recipes
One method to prevent fogging is to apply a thin film of detergentDetergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
, but this method is criticized because detergents are designed to be water soluble and they cause smearing. Divers often use saliva, which is a commonly known and effective anti-fogging agent. Other home recipes exist, including the application of white vinegar with hot water, or a mixture containing sudsy ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
and liquid dishwasher detergent .