question: Why, despite being slippery, isn't water a good lubricant?
comment: Water really is a pretty good lubricant, but its has a few problems. 1) it evaporates. So to use it as a lubricate in a non-air-tight system, you'll have to frequently add more. 2) it is corrosive. It causes metal to rust. 3) microbes can live and reproduce in it. 4) its doesn't lubricate as well as other relatively cheap substances, like oil.
passages: Typical water-based lubricants may be incompatible with sex acts that occur in water (such as in a bathtub, pool, or hot tub) as they can be dissolved or dispersed in water.
   In April 2010, Wet Kiwi Strawberry flavored lubricant was featured in an episode of MTV’s when housemate Andrew picked up a bottle and proceeded to snack on the lubricant by pouring it directly into his mouth. He joked that it was really tasty and he would use it on salads.
   A later study has validated the findings of the Population Council for some water-based products' hyper-osmolality causing some human's cells damage, and better biocompatibility with low-osmolality water-based products and silicone-based products but failed to corroborate polyquaternium 15 having a role that binds HIV to rectal cells or increase HIV replication.
  
  Section::::Types.:By composition.:Oil-based.
   Water-based lubricants, called "emulsions", are the most used type of lubricant, because of health, environmental, and safety reasons. Unlike solvent-based lubricants, if water is properly treated to remove all minerals from it, it will not leave any by-product in the dies. If the water is not properly treated, then the minerals can cause surface defects and discontinuities. There are four types of water-based lubricants: oil in water, water in oil, semi-synthetic, and synthetic. Oil in water is the best, because when the lubricant is applied, the water cools the die surface by evaporating while depositing the oil, which helps release the shot. A common mixture for this type of lubricants is thirty parts water to one part oil, however in extreme cases a ratio of 100:1 is used.
   Free film lubrication theory is concerned with the case in which one of the surfaces containing the fluid is a free surface. In that case the position of the free surface is itself unknown, and one goal of lubrication theory is then to determine this. Surface tension may then be significant, or even dominant. Issues of wetting and dewetting then arise. For very thin films (thickness less than one micrometre), additional intermolecular forces, such as Van der Waals forces or disjoining forces, may become significant.
  
  Section::::Theoretical basis.
   Silicone-based lubricants do not contain any water. They offer a different feel from water-based personal lubricants. Silicone-based lubricants are not absorbed by skin or mucous membranes and consequently last longer than water-based lubricants. Many different silicone lubricants are commercially available, with varying quality and performance. Not all silicone-based lubricants are "certified" latex-safe, but silicone-based lubricants have not been shown to increase the risk of HIV transmission during anal intercourse, as some water-based lubes have.
   BULLET::::- Historically, it is a concern in aqueducts of all kinds, throughout human history. It is also relevant to sewer lines. Systematic study traces back to Henry Darcy, an aqueduct engineer.
  
  BULLET::::- Natural flows in river beds are important to human activity; friction loss in a stream bed has an effect on the height of the flow, particularly significant during flooding.
  
  BULLET::::- The economies of pipelines for petrochemical delivery are highly affected by friction loss. The Yamal–Europe pipeline carries methane at a volume flow rate of 32.3 × 10 m of gas per year, at Reynolds numbers greater than 50 × 10.
   For perfectly good wetting, contact angle ("θ") at equilibrium should be minimized. However, it is valid only at equilibrium, and rate of the equilibrium depends on the balance between driving force of wetting and viscosity of the liquid. In the case of polymer melts, viscosity can be very high and it may take a long time to reach the equilibrium contact angle (dynamic contact angle is likely higher than the contact angle at equilibrium).
   Water-based personal lubricants are water-soluble and are the most widely used personal lubricants. The earliest water-based lubricants were cellulose ether or glycerin solutions. Products available today may have various agents added for even dispersal, moisture retention, and resistance to contamination. The viscosity of these products can be altered by adjusting their water content and concentration of cellulose or other gel-forming hydrophilic ingredient. Because water-based personal lubricants absorb into the skin and evaporate, most water-based lubricants have a tendency to dry out during use, but reapplication of the lubricant or application of water or saliva is usually sufficient to reactivate them. When the lubricant eventually dries out, it may leave behind a residue derived from the other ingredients in the formulation. This may require reapplication during sex, and/or removal of the residue with water. Scientists are testing whether anti-retroviral lubricants or gels can be applied to aid in the prevention of transmission of HIV.
   Section::::Properties.
  
  A good lubricant generally possesses the following characteristics:
  
  BULLET::::- A high boiling point and low freezing point (in order to stay liquid within a wide range of temperature)
  
  BULLET::::- A high viscosity index
  
  BULLET::::- Thermal stability
  
  BULLET::::- Hydraulic stability
  
  BULLET::::- Demulsibility
  
  BULLET::::- Corrosion prevention
  
  BULLET::::- A high resistance to oxidation
  
  Section::::Properties.:Formulation.
   The viscosity of an aqueous solution can either increase or decrease with concentration depending on the solute and the range of concentration. For instance, the table below shows that viscosity increases monotonically with concentration for sodium chloride and calcium chloride, but decreases for potassium iodide and cesium chloride (the latter up to 30% mass percentage, after which viscosity increases). 
  
  The increase in viscosity for sucrose solutions is particularly dramatic, and explains in part the common experience of sugar water being "sticky".
  
  Section::::Viscosities under nonstandard conditions.
  
  Section::::Viscosities under nonstandard conditions.:Gases.
   Section::::Safety.:Nonoxynol-9.
  
  When Wet was launched, AIDS awareness was at a peak and the original Wet product was formulated with Nonoxynol-9, a spermicidal agent that was an ingredient in many mainstream sexual wellness and contraceptive products at the time. In 1996, studies began to question the efficacy of Nonoxynol-9 in reducing HIV transmission, while isolated cases of skin irritation and inflammation were also reported and Trigg Laboratories chose to remove it from their product. While these studies began eleven years ago, it was only in December 2007 that the Food and Drug Administration finally mandated a warning about Nonoxynol-9.
  
  Section::::Manufacturing.
   The Population Council, in a 2011 study, tested commercially available water-based sexual lubricants, and found that many damaged human rectal cells and that some of them - those containing polyquaternium-15 - appeared to actively increase HIV replication in cell cultures and therefore could raise one's risk of HIV transmission. Water-based 'lubes' have been recommended for use in safer sex because they do not weaken condoms like oil-based lubricants do. The researchers concluded: "Since it is the condom that is protecting users from HIV rather than the lube, condom users should still be encouraged to use water-based lubes because condoms are also more likely to break, and trauma to the rectal lining occur, with no lube". They also cited silicone-based lubricants as a potential alternative, although they did not test any silicone lubes in their study.
   BULLET::::- Lionel Barrymore - In First Audience/In Second Audience/Visitor
  
  BULLET::::- Walter Miller - The Idealist's Brother, a Minister
  
  BULLET::::- Clara T. Bracy - The Nurse
  
  BULLET::::- Harry Carey - Stage Manager/At Dinner
  
  BULLET::::- Gertrude Bambrick - Among Dancers
  
  BULLET::::- Kathleen Butler - In First Audience/Among Dancers
  
  BULLET::::- William J. Butler - Among Dancers
  
  BULLET::::- John T. Dillon - In Second Audience/At Dinner
  
  BULLET::::- Frank Evans - In First Audience/In Second Audience
  
  BULLET::::- Dorothy Gish - In First Audience
  
  BULLET::::- Lillian Gish - In First Audience
  
  BULLET::::- Robert Harron
  
  BULLET::::- J. Jiquel Lanoe - In First Audience/Among Dancers
   In May 2010, Wet lubricants were featured on "Tori and Dean: Home Sweet Hollywood" as a part of Tori’s new adventures in wedding planning. Taking on the role of wedding planner for her friend Brandy’s wedding, Tori is charged with flower arrangements, cakes, set-up and the bridal party gift bags, in which she provided a variety of Wet personal lubricants.
   For example, for a Hookean elastic solid, the relaxation time will be infinite and it will vanish for a Newtonian viscous fluid. For liquid water, is typically 10 s, for lubricating oils passing through gear teeth at high pressure it is of the order of 10 s and for polymers undergoing plastics processing, the relaxation time will be of the order of a few seconds. Therefore, depending on the situation, these liquids may exhibit elastic properties, departing from purely viscous behavior.
   Section::::Physics.:Lubrication.
  
  To reduce friction between surfaces and keep wear under control, materials called lubricants are used. Unlike what you might think, these are not just oils or fats, but any fluid material that is characterized by viscosity, such as air and water. Of course, some lubricants are more suitable than others, depending on the type of use they are intended for: air and water, for example, are readily available, but the former can only be used under limited load and speed conditions, while the second can contribute to the wear of materials.
   BULLET::::- In hydropower applications, the energy lost to skin friction in flume and penstock is not available for useful work, say generating electricity.
  
  BULLET::::- Irrigation water is pumped at large yearly volumes of flow, entailing significant expense.
  
  BULLET::::- HVAC systems pump conditioning air on a widespread basis.
  
  BULLET::::- In refrigeration applications, energy is expended pumping the coolant fluid through pipes or through the condenser. In split systems, the pipes carrying the coolant take the place of the air ducts in HVAC systems.
  
  BULLET::::- Wells and domestic water systems must be engineered for effective and economical operation.
  
  Section::::Definition.
   BULLET::::- William Hanna as Tom Cat (uncredited)
  
  Section::::Production.
  
  The film was based on a story by Dorothy Kingsley. MGM liked it, bought it and hired Kingsley to develop it into a screenplay. It was originally called "Everybody Swims" and was intended as a vehicle for Esther Williams and Debbie Reynolds.
  
  In the underwater sequences in which Williams speaks to Tom and Jerry, Joseph Barbera had pink bubbles drawn coming out of her mouth for a cost of $50,000.
   Friction is desirable and important in supplying traction to facilitate motion on land. Most land vehicles rely on friction for acceleration, deceleration and changing direction. Sudden reductions in traction can cause loss of control and accidents.
  
  Friction is not itself a fundamental force. Dry friction arises from a combination of inter-surface adhesion, surface roughness, surface deformation, and surface contamination. The complexity of these interactions makes the calculation of friction from first principles impractical and necessitates the use of empirical methods for analysis and the development of theory.
   BULLET::::- is known as surface concentration, it represents excess of solute per unit area of the surface over what would be present if the bulk concentration prevailed all the way to the surface. It has units of mol/m
  
  BULLET::::- is the concentration of the substance in the bulk solution.
  
  BULLET::::- is the gas constant and the temperature
  
  Certain assumptions are taken in its deduction, therefore Gibbs isotherm can only be applied to ideal (very dilute) solutions with two components.
  
  Section::::Thermodynamics.:Thermodynamics of soap bubbles.:Influence of particle size on vapor pressure.
   Section::::Misconceptions.
   BULLET::::- is the surface tension of the liquid in dynes per centimeter or newtons per meter.
  
  BULLET::::- is the acceleration due to gravity and is equal to 980 cm/s or 9.8 m/s
  
  BULLET::::- is the density of the liquid in grams per cubic centimeter or kilograms per cubic meter
  
  In reality, the thicknesses of the puddles will be slightly less than what is predicted by the above formula because very few surfaces have a contact angle of 180° with any liquid. When the contact angle is less than 180°, the thickness is given by:
   The sensor does not have any physically given hysteresis as it is known from capacitance hygrometers and sensors, and does not require regular cleaning as its surface is not the effectively sensing element. Volatiles, in principle, influence the measurement performance—especially those that dissociate in the electrolyte and thereby change its resistance. Such influences can easily be avoided by using chemical protection filters that absorb the volatile compound before arriving at the sensor.
  
  Section::::Measurement.:Capacitance hygrometers.
   It is estimated that 40% of all lubricants are released into the environment. Common disposal methods include recycling, burning, landfill and discharge into water, though typically disposal in landfill and discharge into water are strictly regulated in most countries, as even small amount of lubricant can contaminate a large amount of water. Most regulations permit a threshold level of lubricant that may be present in waste streams and companies spend hundreds of millions of dollars annually in treating their waste waters to get to acceptable levels.
  
presuppositions: Water is not a good lubricant water is not a good lubricant.
corrections: Water is a good lubricant, but it evaporates, is corrosive, can contain microbes, and isn't as good a lubricant as oil. Water really is a pretty good lubricant.
raw_presuppositions: Water is not a good lubricant water is not a good lubricant.
raw_corrections: Water is a good lubricant, but it evaporates, is corrosive, can contain microbes, and isn't as good a lubricant as oil. Water really is a pretty good lubricant.