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How to freeze something quickly?

Ice makers can be finicky. If you only visit the ice dispenser a couple of times per day, it may never have occurred to you to think much about the volume of ice production or if the ice maker is slow to make ice. But as demand for ice increases, you may begin to wonder, “How long should an ice maker take to make ice?”

FAQ: How Long Should an Ice Maker Take to Make Ice?

Typical Ice Maker Production

Your ice maker is one of the hardest working features of your refrigerator/freezer. The freezer compartment is cold enough to keep everything frozen, but remember, it doesn’t always start out that way.

It may seem that the ice maker is slow making ice, but to some degree, that’s normal. The water has to fill the tray, freeze, and dump in the holding tray, which all takes time.

This ice cycle time does vary a bit, as does the volume of ice produced, depending on the size of the tray the cubes are being dumped into. Generally speaking, about 130 ice cubes are being produced in a 24-hour period.

A typical ice maker tray will hold 4-11 pounds of ice. A typical ice maker produces 3-7 pounds of ice. If the ice tray is being emptied due to usage, the cycle will continue to initiate. If the ice sits there for a few days, the cycle will pause. Again, the wiggle room depends on your particular make and model, the size of the holding tray, and how much ice is being removed throughout the day.

Typical Ice Maker Cycle Time

So how long should an ice maker take to make ice? Well, understanding the process to make it happen will help. The way the ice maker works is to complete what is called a cycle. The cycle goes through these steps to make ice:

  • Ice maker module fills tray with water
  • Water freezes
  • Ice maker dumps ice cubes into holding bin
  • Ice dispenser (if applicable) shoots ice into your glass

Simple, but nevertheless, a process. As much of a superhero as your ice maker is, it can’t complete a cycle instantaneously. A high quality refrigerator will complete an ice maker cycle time of about 90 minutes, producing anywhere from 8-10 ice cubes.

This cycle time does vary a bit, as does the volume of ice produced, depending on the size of the tray the cubes are being dumped into.

Troubleshooting an Ice Maker That’s Too Slow

How long should an ice maker take to make ice? Sometimes it feels like forever! If you have waited over an hour and your ice maker is not making ice, then something could be wrong. Try these DIY tips to see if you can correct the problem on your own or if you need to contact a technician for ice maker repair.

Check to make sure the door is closed completely: A door ajar may keep the ice maker from functioning.

Check to see if the ice maker is off: Sometimes, the feeder arm accidentally gets stuck in the off position; just release it to initiate the cycle.

Check to see if your water filter needs to be changed: A clogged filter can restrict water flow, which reduces the pressure needed to fill the ice trays.

Does a full freezer freeze items faster than an empty one?

Heat Capacity

You are comparing two situations, and to formalize this, let’s say that the freezer has a given volume, $V$ and that volume is broken down into air and other frozen materials. Then we have the situation that $V=V_{air}+V_{stuff}$. The heat capacity of the entire freezer between the two situations will be vastly difference because the volumetric heat capacity for air and ice (which is the most common item included in “stuff”) is vastly different by a factor of about 1000. I’ll use the Wikipedia notations, where specific heat capacity is $c$ ($\frac{J}{kg K}$) and volumetric heat capacity is $c \rho$. The volumetric heat capacity times volume is the heat capacity (denoted $C$) so for the entire freezer we have the following.

$$C = \left(V c \rho \right)_{air} + \left( V c \rho \right)_{stuff}$$

The heat capacity matters because should you insert some mount of heat into the freezer, $Q$, then after equilibrium is reached, the temperature will raise by:

$$\Delta T = \frac{Q}{C}$$

So if we don’t consider the work of the freezer thermal cycle actively cooling the air, then the freezer with more stuff in it will cool the item faster because the temperature of the air+stuff changes less, so the $\Delta T$ in the Newton cooling model will be greater and it will cool faster and cool to a lower temperature.

Air Cooling

It is relevant to note that the air is actively cooled by the freezer systems and the stuff is not. This is interesting because it will have relevance to the heat transfer mechanisms (more later). Although this isn’t entirely correct, we could assume that the cooling device takes some flow rate of air continuously, $\dot{m}$ (kg/s), and cools with some enthalpy change, $\Delta h$ (J/kg). That enthalpy change removes heat from the system, but that doesn’t change from one case to the other.

But that can’t be the full picture. Heat is only removed from the freezer if the temperature drops below a certain value. So, another way to do this may be to assume that the cooler keeps the air at a certain temperature, but that may defeat the purpose of the problem. It is also possible that the thing being cooled, in fact, outpaces the cooling device and heats the air faster than it can be cooled. In that case the air temperature would rise above the programmed setpoint and stay there until the item being cooled started to approach the freezer temperature.

Heat Transfer Mechanisms

There are two mechanisms of heat transfer between the item you are freezing and other stuff in the freezer.

  • Convection with the air
  • Radiative heat transfer with other items and the walls
  • Conduction with the bottom surface (same for both and I won’t discuss)

Obviously, the 1st one transfers with the air and the 2nd one transfers with the stuff. I would like to propose several simplified models such that we can talk more specifically about predictions.

  1. The freezer cools the item faster than the active cooling is relevant
  2. The item quickly equilibrizes with the air, then the stuff and the active cooling then slowly lowers the temperature
  3. The air is kept at a constant temperature

As I’ve said already, number 1 clearly has the freezer with more stuff win. Number 2 could potentially go in the direction of the freezer with less stuff because of the larger heat capacity of air (which will only work for a small item), but the radiative heat transfer still advantages the case with more stuff. In number 3 the freezer with more stuff clearly wins unless the flow path for convection is restricted.

The exact one that will win does depend on the specific values for the system, so that’s in the hands of the experimentalist. Generally though, the higher heat capacity and the ability to transfer heat through radiative transfer is likely to favor the freezer with more stuff in it.

When you need ice cubes the most is usually the one time you forget to fill your ice cube trays with water. This is especially inconvenient if you’re having guests over and need ice to put in their drinks. Luckily, you do have some options when you need to make ice fast.

Try out these tricks the next time you need ice but can’t afford to wait for it to freeze.

How Long Does it Normally Take to Freeze Water?

swiggle1 dot pattern2Source: LiveScience

Normally, it takes anywhere from three to four hours for water to freeze in your freezer at home. Water freezes after its temperature reaches 32 degrees Fahrenheit, though this can depend on a variety of factors, including:

  • The size of the cubes
  • The air temperature in the freezer
  • Whether there are any food items at room temperature in the freezer

How Increasing the Water Surface Area Can More Quickly Freeze Water

swiggle1 dot pattern2Source: The Chuggernauts

Increasing the surface area of the water in contact with the cold air of your freezer can make it freeze faster. The optimal way to freeze ice is by using ice trays specially designed for this purpose. The water in an ice tray designed to make small ice cubes will also freeze faster.

swiggle1 dot pattern2Source: newair

Also, ice trays with an empty space between each cube allows the water to freeze faster due to increased contact with the cold air.

The Mpemba Effect and How it Works

swiggle1 dot pattern2Source: Digital Trends

Another way to freeze water fast is by using hot water instead of cold. This should only take about two hours compared to three or four hours. Believe it or not, hot water actually freezes faster than cold water under the same conditions. But how exactly does it work?

swiggle1 dot pattern2Source: Science Alert

The process is named after Erasto Mpemba, the Tanzanian student who discovered it. The phenomenon actually goes back further than that to Aristotle in the 4th Century AD, though Mpemba was the first person to actually study it, along with his professor, and write a paper about the effect in 1969.

The way the Mpemba Effect is thought to work is through the faster freezing rate created by currents and temperature gradients that form in the heated water. These currents and gradients allow the water to cool much faster because it contributes to the quick release of heat from the water’s surface.

Other Explanations for the Mpemba Effect

swiggle1 dot pattern2Source: Tech-Faq

In addition to the above-mentioned explanation for the Mpemba Effect, there are some other theories as to why this rapid freezing occurs, including:

  • Evaporation: One theory holds that evaporation of the hot water reduces the overall mass of the water to be frozen. And while some feel this is a contributing factor, it does not account for the whole effect.
  • Dissolved Gases: Cold water is said to contain a higher number of dissolved gases, which contribute to its slower cooling process when compared to hot water, which contain fewer gases.
  • Hydrogen Bonding: The rate of hydrogen bonding is another factor that is believed to contribute to hot water freezing faster as compared to cold water. This reduction in the hydrogen bonds found in hot water means temperatures are more evenly distributed as the water freezes, making it freeze faster.

Use an Ice Maker to Make Ice Cubes Fast

swiggle1 dot pattern2Source: Compact Appliance

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If you really want to make ice fast without having to use hot water, buy an ice maker. An ice maker freezes water by exposing the water in the metal ice tray directly to the compressor coils. This in turn results in a faster production of ice as opposed to using a standard ice cube tray.

Source: One Good Thing by Jillee

Cheryl Knight [email protected] Cheryl Knight is a contributor at Home Hacks.

We Had No Idea THIS Is The Right Way To Make Ice

We just found out we’ve been making ice the wrong way our entire lives, according to science. Apparently filling your ice cube tray with hot water can really cut down on freezing time. It’s a bit counterintuitive, we know, but this is a real scientific phenomenon known as the Mpemba effect. The paradoxical effect was named after Erasto Mpemba, a Tanzanian student who noticed that a hot ice cream mix froze faster than a cold one. He then published a paper on this scientific anomaly in 1969. No one has ever been able to definitively explain why hot water freezes faster, but there are several theories. Some scientists believe faster evaporation of hot water reduces the volume left to freeze. Others say the formation of a frost layer on cold water acts as an insulator, which contributes to a slower freezing rate. No matter what the actual scientific explanation is, we’re eternally grateful to Erasto for this beyond helpful tip. (Mic) Want more R29 Food?
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How Does This Even Work?

The phenomenon of hot water turning into ice faster than cold water is known as the Mpemba effect, named after a Tanzanian student who observed his hot ice cream mix freezing more rapidly than the cold version.

Separating homemade ice cream into ice cube trays also speeds up freezing. Image by J. Kenji Lopez-Alt/Serious Eats

A recent study by Xi Zhang, Zengsheng Ma, and Chang Q Sun at Nanyang Technological University, Singapore, helps shine some light on a possible reason why this phenomenon occurs.

A water molecule is made up of two hydrogen atoms and one oxygen atom which are bound together by the sharing of electrons, known as a covalent bond. Water molecules are then connected to each other by intermolecular forces known as hydrogen bonds, which happens when a hydrogen atom from one water molecule is near an oxygen atom from another.

H2O: Just one big happy family. Image via Lightbulb Books

As you can see from the above illustration, the three atoms together form an angle. A hydrogen bond is the result of this structure and is responsible for giving water its unique life-giving properties and its ability to expand when frozen.

According to the Nanyang study, these bonds are behind the Mpemba effect, when hydrogen bonds do their job and bring water molecules into close contact. However, the molecules have a natural repulsion to one another. This action by the hydrogen bonds makes the covalent bonds move apart and store energy.

As liquid is heated, the hydrogen bonds stretch and water molecules are forced to be farther apart. Correspondingly, the covalent bonds within the water atoms shrink and lose energy. This process is akin to cooling off.

On a molecular level, this water is already cooled off. Seriously. Image via The Dabblist

Essentially, hot water already closely resembles cool water on a molecular level. The energy in hot water is wound up so tightly that when it is released, it cools and freezes faster than cold water.

Determining whether or not hot water can freeze faster than cold water may seem like a no-brainer. After all, water freezes at 0 degrees Celsius. And wouldn’t water hot enough to kill E. coli bacteria (about 120 degrees Fahrenheit or 50 degrees Celsius) take a longer path than cooler water at a fall New England beach (about 60 degrees Fahrenheit or 15 degrees Celsius) towards a frigid future as ice? While a logical assumption, it turns out that hot water can freeze before cooler water under certain conditions.

This apparent quirk of nature is the “Mpemba effect,” named after the Tanzanian high school student, Erasto Mpemba, who first observed it in 1963. The Mpemba effect occurs when two bodies of water with different temperatures are exposed to the same subzero surroundings and the hotter water freezes first. Mpemba’s observations confirmed the hunches of some of history’s most revered thinkers, such as Aristotle, Rene Descartes and Francis Bacon, who also thought that hot water froze faster than cold water.

Evaporation is the strongest candidate to explain the Mpemba effect. As hot water placed in an open container begins to cool, the overall mass decreases as some of the water evaporates. With less water to freeze, the process can take less time. But this doesn’t always work, especially when using closed containers that prevent evaporated water from escaping.

And evaporation may not be the only reason the water can freeze more quickly. There may be less dissolved gas in the warmer water, which can reduce its ability to conduct heat, allowing it to cool faster. However, Polish physicists in the 1980s were unable to conclusively demonstrate this relationship.

A non-uniform temperature distribution in the water may also explain the Mpemba effect. Hot water rises to the top of a container before it escapes, displacing the cold water beneath it and creating a “hot top.” This movement of hot water up and cold water down is called a convection current. These currents are a popular form of heat transfer in liquids and gases, occurring in the ocean and also in radiators that warm a chilly room. With the cooler water at the bottom, this uneven temperature distribution creates convection currents that accelerate the cooling process. Even with more ground to cover to freeze, the temperature of the hotter water can drop at a faster rate than the cooler water.

So the next time you refill your ice cube tray, try using warmer water. You might have ice cubes to cool your drink even sooner.

This answer is provided by Scienceline, a project of New York University’s Science, Health and Environmental Reporting Program.

Follow Life’s Little Mysteries on Twitter @llmysteries. We’re also on Facebook & Google+.

How Icemakers Work

Only a century ago, ice was hard to come by in most parts of the world. In hotter climates, you had to buy your ice from a delivery service, which imported hefty blocks from a colder climate or from an industrial refrigeration plant. The price of ice was relatively steep, but if you wanted to keep your food cold, you didn’t have much choice. In the hottest parts of the world, ice was a rare luxury. In an equatorial country, you might live your whole life and never even see a piece of ice.

This all changed in the early 20th century. Compact, affordable refrigerators brought the means of food preservation and ice production into the home and corner store. In the 1960s, new automatic icemaker machines made life even easier. These days, most Americans take ice completely for granted, even during the hottest days of summer.

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In this article, we’ll find out what’s inside a typical home icemaker, as well as the larger commercial icemakers you might find at a hotel or grocery store. As we’ll see, the basic process of making ice is very simple — you just freeze water — but spitting out perfectly shaped ice cubes is a fairly elaborate process.

The home icemaker’s predecessor was the plastic ice tray. It’s fairly obvious how this device works: You pour water into a mold, leave it in the freezer until it turns to a solid and then extract the ice cubes. An icemaker does exactly the same thing, but the process of pouring water and extracting cubes is fully automated. A home icemaker is an ice-cube assembly line.

The home icemaker is a miniature ice-cube assembly line.

Most icemakers use an electric motor, an electrically operated water valve and an electrical heating unit. To provide power to all these elements, you have to hook the icemaker up to the electrical circuit powering your refrigerator. You also have to hook the icemaker up to the plumbing line in your house, to provide fresh water for the ice cubes. The power line and the water-intake tube both run through a hole in the back of the freezer.

In the next section, we’ll look at the cycle an icemaker goes through to make ice.

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I started thinking about faster ways to make ice cubes after our automatic ice making contraption broke and the repair guy told me it wasn’t worth fixing. So I won’t go into all the things I didn’t know about freezers, just the stuff I didn’t know about making ice cubes.

The Tray

I remember having metal ice cube trays with a lever when I was a kid long ago and far away. Now they seem to be mostly plastic, but lately some are made of silicone. For speed, metal is the way to go because of its little insulation, although it tends to cost more.

Water Quality

Dissolved minerals in water tend to lower the freezing point. The surfaces tend to freeze first because this is pure water. The impurities concentrate in cloudiness in the middle. Water in Vancouver is soft, so it has fewer minerals. Our ice cubes are still cloudy in the middle, but I see bubbles in there, probably from trapped gases. Commercially produced ice is made with a flowing source of purified water so the bubbles get washed away as the ice forms from below.

Water temperature

I assumed that colder water would freeze faster (and of course it is cold just before it freezes). But the Mpemba effect says that warmer water placed into the cold can freeze faster.

In the 1960s, a high school student in Tanzania named Erasto Mpemba wondered why, when his class made ice cream, warm milk froze faster than cold. He questioned his teachers and did experiments with water to verify that it happened. I think this is an awesome example of asking questions of authorities. The tricky thing is that it doesn’t always happen and it seems difficult to control just the variables you want to compare.

Brownridge found that hot tap water had a higher freezing point and froze faster than cold distilled water, but that isn’t just changing temperature. Here are some suggestions for why:

  1. Evaporation – If you use hot water, then it evaporates more quickly so you have less water left over, which can then freeze more quickly. But the Mpemba effect can occur with closed containers.
  2. Supercooling – Hot water is less likely to undergo supercooling when it is below 0 degrees Celsius.
  3. Dissolved gases – Hot water may lose some of the dissolved gases, and the resulting water might freeze faster. If you used boiled water to make ice cubes they are supposed to be clearer.
  4. Convection – Hot water could result in more circulation of the temperature and result in more rapid cooling.
  5. Surroundings – If you have a freezer with frost and you put something hot on it, that will defrost it and then cool more effectively. This might be especially true with metal ice cube trays and old fridges with the little ice cube making compartments that get all frosted up.

So why warmer water would freeze faster is still open to discussion. I just found that the Royal Society of Chemistry in Britain and Hermes 2012 offered a prize of £1000 (over $1500 Cdn) this summer for the best explanation for the Mpemba effect (sorry, it’s too late to enter!). They received 22,000 responses and at the time of this post, were still processing them.

All this investigation has given me pause. Am I so busy that I cannot even let my ice cubes freeze as they will? I’ve decided that it is me and not the ice cubes that need to chill.

Nonetheless, if you have ice cube freezing tips, let me know.

​What’s Happening:
Most people believe water always freezes at exactly 32°F or 0°C. While it is true that pure water ice always begins to melt at 0°C, liquid water- even pure water- does not necessarily freeze at this temperature, and can remain a liquid at much colder temperatures (see the link below). This is called supercooled water. The reason this can happen (not just for water, but for many substances that form crystals in their solid state) is that molecules of a liquid behave a little differently than those in either the solid state (where they are tightly locked into an orderly arrangement or crystal lattice) or gas state (where they are completely independent). All that is needed for a solid to melt is heat, which provides the energy for the crystal lattice to break apart and become liquid. On the other hand, simply cooling the molecules in a liquid does not make them form a solid. The molecules must begin to arrange themselves and form an orderly crystal lattice, and this takes a little more energy (this sort of “borrowed” energy is called the latent heat of fusion). Think of it this way: it’s much easier to destroy a boat than it is to build one from scratch. It takes some thought and care to start building your boat from the individual pieces. Forming a solid from individual liquid molecules is similar, the first few molecules must move into proper position and alignment to start building correct crystal lattice. Once this lattice begins to form, it becomes much easier for other liquid molecules to attach and continue growing the crystal lattice. The colder a liquid becomes, the more likely it is that some of the molecules will form that first crystal, but if they are not moving around much it may not happen. That’s why we were very careful not to disturb the bottles until we wanted them to freeze. Tapping or shaking the bottle got the molecules moving around so that it became more likely that a few would move into the proper arrangement and form a crystal (called a seed crystal), then the rest of the molecules quickly attached, and the entire bottle froze.

The freezing or melting point of a substance is actually defined as the temperature at which the liquid and solid phases are in equilibrium. For pure water this means that ice is melting at exactly the same rate that liquid water is freezing so that the net amount of each stays about unchanged, and that occurs at exactly 0°C. This perfect equilibrium might seem very difficult to achieve, but actually as long as your bath contains plenty of both ice and water, and you are not adding or removing too much external heat (i.e. the cooler is well insulated), the phases will find their equilibrium and the temperature stabilize ayt 0°C. That’s why you should have measured 0°C (depending on the accuracy of your thermometer) in step 2. When the water in a bottle is supercooled (below 0°C) it is not in equilibrium, since there is no ice. But once the first solid crystal forms, the amount of ice increases as more water freezes and the mixture quickly reaches equilibrium at 0°C- i.e. the temperature actually goes up as the water freezes, releasing the latent heat of fusion (see Additional Experiments below). That’s why the ice in the bottle is very soft and slushy, rather than frozen hard. To freeze the bottle hard you must remove this extra heat somehow, perhaps by placing it back in the cooler.
To supercool a water bottle you lower it’s temperature below the normal equilibrium freezing point by removing heat. Since heat only flows from hotter objects to colder ones, you need to place your bottle in contact with something colder, such as the cold air in a freezer. But most home freezers are typically set at about -20 to -40°C, so leaving the bottle in the freezer too long will lower the temperature so much that it is almost certain to form a seed crystal somewhere then freeze completely. Unless you can put a thermometer inside the bottle, you must check it often and remove it once it is supercooled but not frozen, which can be tricky. Another problem with this method is that most freezers use motors which cause vibrations, and just like when you tapped the bottle, can form a seed crystal and freeze the water. You could use the ice water bath you prepared in Step 2 to cool the water, but this bath is in equilibrium at 0°C, so you can only cool your bottles to this temperature, which is not cold enough to instantly freeze the water. To supercool your bottles you need an ice-water bath that is much colder than 0°C.
Fortunately liquid water (or any solvent) has another very useful property- the freezing point of a solution (anything dissolved in a solvent) is always lower than the freezing point of the pure solvent. In our case this means that dissolving salt in water (the solvent) lowers the freezing point of the salt-water solution, i.e. you must get it colder than pure water before it will freeze. This is why it is much harder to freeze sea water than fresh water. Note that this is not the same as supercooled water; the salt-water is a solution, not pure water. This is also why you sprinkle salt on an icy road to melt it. The salt dissolves into the thin layer of liquid water that is usually present on the surface (unless the icy is very, very cold), lowering the temperature required for the ice to remain frozen. The more salt you dissolve, the lower the freezing point. It doesn’t matter what kind of salt (or anything else) you use, only how much you dissolve in the water. This is called a colligative property, meaning that it depends only on the number of particles, not their type. Since solid ice is usually much colder than 0°C (you measured that in Step 1), adding ice to a salt water solution lowers the temperature of the solution. And since the freezing point of this salt-water-ice solution bath (the temperature where freezing and melting is in equilibrium) is lower that that of a pure water-ice bath, we can use this to supercool our bottles of pure water. By adding enough salt it’s relatively easy to prepare a bath that is -10°C or colder.
Variations and Related Activities:
There are other interesting ways to instantly freeze supercooled water. Very carefully unscrew the top from one of your bottles without freezing the water. Drop a small piece of ice into the water and watch as it instantly initiates freezing in the bottle. Since this piece is already solid, it serves as the seed crystal to which the liquid molecules can easily attach. You can also try slowly pouring liquid supercooled water from the bottle onto a dish with a small piece of ice. The water will freeze as it hits the ice then continue freezing right up the pouring stream and into the bottle. For another experiment, carefully place a thermometer in the bottle of supercooled liquid water. It should read a temperature well below 0°C. Now drop a small piece of ice into the bottle to initiate freezing and observe the temperature rise as the water freezes, until it finally reaches 0°C. As water freezes it releases heat (called the latent heat of fusion), and this heat has nowhere to go except into the rest of the water and ice in the bottle, which actually remelts some of the ice that has just frozen. This is why the bottle doesn’t freeze into hard ice, but forms a very wet, slushy ice. Since the ice and water is now in equilibrium, its temperature must be at the freezing point, or 0°C.

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