Our beloved kitchen product – the aluminum foil – has two completely different faces! One side of the sheets shines as if it is the moonlight itself, the other not so much. This gives rise to two questions:

  • Why are there two sides that look exactly the opposite of each other?
  • Which side should you use in the kitchen?

Why

People will give you all sorts of theories to explain why this is so. One popular one that has been making its rounds is that the reason household aluminum foil has a dull and a shiny side is scientific. The shiny side will reflect the heat on to whatever you have in the oven. This is also supported by the scientific principle of light and heat reflection by shiny surfaces.

If that were true, turning on your kitchen grill and placing your hand on its side would not prove that the dull side reflects heat equally well. Hold the piece of aluminum foil to reflect the heat from the heating element in the grill to your hand. Repeat the experiment with both sides of the foil and you will have your answer: both sides reflect heat equally.

The real reason behind this is nothing more than the way aluminum foil is produced. To roll the foil down to the cooking-appropriate thickness (approximately 0.01 mm), a rolling mill is used. This mill presses down two coils simultaneously by a process called ‘doubling’. The side that encounters the rolling mill is the external side while the inner surface stays safely tucked in. That is why the external side is shiny and the internal is matt for both the coils.

Which

With the short experiment above, it is plain for anyone to see that while some cooks might prefer to use one side or the other during cooking, both sides reflect heat equally. In another experiment, two baking pans were used. One had bacon that was covered with the foil, shiny side up while the other bacon bundle was covered with foil shiny side down. To the center of both meats was added a probe thermometer. On baking the piece of bacon, it was discovered that both took the same amount of time to reach the same temperature. When the foil sheets were cracked open, both revealed crisp bacon in all its golden glory!

Final verdict for all foil-lovers: use the side you want!

Drop by to tell us which side of foil you prefer to use and why! Symintec, we bridge the gap between you and success with quality aluminum!

The ever-amazing aluminum foil actually contains between 92-99 percent aluminum and is made from an alloy of the metal. Depending upon its usage, this product is manufactured in varying thickness that can range from 0.00017 to 0.2 inches.

Some of its many uses include:

  • Air conditioner fin stocks
  • Television and radio capacitors
  • Thermal insulation
  • Transformer electrical coils
  • Decorative items
  • Packaging and Containers
  • Storage Tank Insulations

 

If you want to know more aluminum foil uses, please check the articles:

1. Aluminum foil — A Product With a Million Uses

2. The Magic Continues — Aluminum Foil Treatments For Diseases

3. 5 Reasons Aluminum Foil Might Be Advancing Science

4. Ten Uses of Aluminum Foil You Never Knew Existed

5. All That Glitters — Which Side of Aluminum Foil Should You Use

What makes aluminum foil so popular and its uses so widespread is that the raw materials required to manufacture it are present in abundance.

Another advantage is its relative inexpensive nature that makes it affordable to almost everyone. Other qualities, such as its durability, non-toxicity, and being greaseproof also add to its charm.

Often used in science labs because it is resistant to many chemicals and can be used to shield apparatus and appliances from both electrical and magnetic interference.

HOW IT IS PRODUCED?

SUMMARY

To extracting pure aluminum, the bauxite ore is used. The extraction is essentially a two-step process.

In the first step, bauxite is separated from the impurities that it may contain. These include:

  • Silica
  • Iron oxide
  • Titanium

 

When purified aluminum oxide is produced, it is then smelted so that only aluminum is left behind.

Then the aluminum will be rolled and the result is the foil that you purchase from the market.

REFINING

This procedure is completed in four steps, which are digestion, clarification, precipitation, and calcination.

In the first stage or digestion, the bauxite ore is first ground to a powder. It is then mixed with sodium hydroxide. After that, this mixture is pumped into huge tanks, called digesters, which are pressurized. In the digesters, the combined mixture of bauxite and sodium hydroxide is broken down by the action of heat and pressure. The ore transforms into its next state i.e. sodium aluminate saturated solution. Any contaminants that are insoluble will settle down at the bottom.

Now starts the next phase of clarification.

In this process, the saturated solution of sodium aluminate, as well as, the contaminants are both sent through a set of presses and tanks. The filters that are present in those tanks will trap the contaminants. The contaminants will then be disposed off, leaving behind a clean solution of sodium aluminate. This solution is filtered once again before it is sent to a cooling tower.

The third stage or precipitation entails that the aluminum oxide solution be sent to a large silo. When that happens, aluminum oxide is then seeded with hydrated aluminum crystals. This leads to the formation of aluminum particles. Soon the seeding crystals will attract the other crystals and soon they will join. These huge aggregates are actually made of aluminum hydrate. The aluminum hydrate clumps will first be filtered out of the solution before being rinsed.

The previous step leads to Calcination, which is the final step of the refinement process. In this phase, the aluminum hydrate is exposed to heat. The extreme temperature will result in dehydration of the material until all the water is dried. The residue will consist of aluminum oxide, a fine white powder.

SMELTING

During smelting the aluminum oxide that was produced after refinement is used to produce pure aluminum metal that can be used to make foil.

The first step in this procedure involves the dissolving of aluminum oxide in a smelting cell. This cell is actually a mold made out of steel and its depths, as well as, walls are lined with carbon. A heated liquid cryolite solution fills that cell.

Cryolite is a conductor and also an aluminum compound.

When an electric current passes through cryolite, it will result in the formation of a crust atop the molten aluminum oxide. More and more aluminum oxide is added and stirred into that mixture, which breaks the crust and it then becomes a part of the mixture as well.

The dissolving aluminum oxide then decomposes electrolytically to produce pure, molten aluminum. The metal keeps on forming white layers at the bottom of the smelting cell. The oxygen that is released from the breaking aluminum oxide will combine with the carbon lining the cryolite cell to produce carbon dioxide gas.

The molten and purified aluminum can now be extracted from the cells. It is transported to crucibles and poured into furnaces. This is the part where the manufacturers may add other elements to the molten form of aluminum. They do this in order to produce aluminum alloys. Each alloy will have specific characteristics depending upon how the end product will be used.

Next, this liquid – with or without additions – will be poured into casting devices. These devices can directly chill the aluminum into large slabs or “ingots”. The ingots, however, cannot be used to produce foil before being annealed. This means they are treated with heat to improve workability. After annealing, the ingots can be rolled into foils.

Heavy rollers are used to where the aluminum ingot is rolled to produce foil. Since two sheets of aluminum are rolled at the same time by one rolling machine, both sheets will come out in the same way. One side will have the natural finish that is bright while the other side will have a matte finish. Knives in the shape of circles will then be used to cut the foil that emerges from the rollers into rectangular sheets.

ROLLING

The rectangular sheets emerging from the rollers are not the final product.

Instead,

they are called foil stock and must be reduced in thickness before they can be called the end product.

To make the foil, a rolling mill is used through which the material gets passed more than once. The metal rolls of the rolling mill are called work rolls and they squeeze the aluminum sheets or webs until they get thinner.

These sheets are then extruded through gaps found between the rolls.

After the work rolls, the job falls to the backup rolls that are heavier. The backup rolls will again apply pressure on the work rolls to increase their stability. Both pairs of rolls rotate in opposite directions and produce foil that can tolerate a wide variety of conditions. For an effective and smooth rolling process, lubricants will be added to the rollers. While the aluminum is undergoing rolling, it must be annealed continuously so that it stays workable because of the heat treatment.

The foil sheet reduction can be controlled by the following factors:

  • Speed of the rolls
  • Viscosity
  • Quantity of the foil
  • Rolling lubricant temperature

 

How thick or thin the foil will be determined by the gap between the rolls. To adjust this gap, the upper work roll can be lowered or raised. Some foil sheets also have patterns on them. These patterns can be produced by different mechanical finishing methods. These methods take place during converting operations.

When the foil sheets exit from between the rollers and are cut with circular razor like knives that are a part of the rolling mills, they are also trimmed and slitted. Trimming is done on the foil edges while during slitting, aluminum foil is cut into sheets the foil into several sheets.

After all these steps,

the foil that is produced has narrow coiled width and is the familiar rectangular shape that we see in the market. The foil may also be from laminated or coated stock. There are also some converting and fabricating operations where the aluminum webs break during the rolling process.

In that case, the broken webs need to be joined through splicing.

There are a few types of splicing that are used in the industry to join plain or backed foil. These include a heat-sealing tape, ultrasonic, electric welding, and pressure-sealing tape. When using the ultrasonic splice, overlapped metal is welded in the solid state by an ultrasonic transducer.

FINISHING

When the usage requires that foil be used in combination with other materials, it will be in different forms.

Aluminum foil may be coated to make it heat-sealing, protective, or decorative uses. The coating can be a variety of materials:

  • Resins
  • Polymers

 

Alternatively, aluminum foil can be laminated to

  • Plastic Films
  • Paperboards
  • Papers

 

Yet another way is to give the foil different shapes. This means aluminum foil can be:

  • Anodized
  • Cut into different shapes
  • Embossed
  • Printed
  • Slit into strips
  • Etched
  • Made in the shape of sheets

After the final shape has been given to the foil, it is ready to be packed and transported to the customer. Both the ways of packaging and transporting will depend on the state of the foil.

QUALITY CONTROL

While factors like time and temperature are controlled in-process, certain requirements must be met when it comes to the finished foil product.

For a product that performs satisfactorily, the foil surface needs to have a particular degree of dryness, depending upon its use. This is ensured by using different converting processes during manufacturing and then tested with a wettability test.

To determine the degree of dryness, the final product is tested with ethyl alcohol solutions. Using distilled water in different volumes so that every solution has ten percent more alcohol, the solutions are poured in a uniform stream on the surface of the foil. Wettability is considered zero, if no drops form and the experiment is continued until the alcohol solution that wets the foil surface completely can be found.

Similarly, properties like tensile strength and thickness are also tested because they will affect how the product can be used.

To test such important properties, standard test methods have been devised.

For instance,

when it is thickness that needs to be determined, a sample of the foil is weighed.

Then its area is measured and the density of the alloy is noted down. The weight is divided by the product of the area and alloy density for the final answer.

To keep the tensile strength of aluminum foil                 in check, special care is taken that no rough edges or even the smallest of defects are prevented.

Testing the tensile strength involves gripping the foil sample in some sort of a vise and applying tensile/pulling force. The force is increased until the sample fractures.

This force is then measured as the tensile strength of the foil sample.

While the Industrial Revolution was promising better literacy for the modern people, advertising and showcasing how it was increasing our ability to better read the “Book of Nature”, the leaders of the new mechanical age realized that the metal that made their world (Iron) lacked certain qualities.

It was not perfect.

This became apparent when we moved from the “horse-carriage” age to that of automobiles and mass consumerism.

One wonders why the leaders did not realize what their reading classes at the industrial plants were pumping into the environment. We only realized climate change in the environment after a hundred years.

But this post is about industrial grade Aluminum and what makes it the universal choice for so many industries.

 

WHAT EVERY PERFECT MATERIAL SHOULD LIKE

So, what would the perfect material be for our new age? Obviously its properties would be defined by the new production line developed in USA and its inherent values of increasing marginal utility for the industry.

First and foremost, the material should be relatively inexpensive and plentiful. The engineers stepped in and claimed: It should be light-weight, strong, resistant to corrosion and heat, and should be a good conductor for electricity. And ofcourse, because we love to experiment, it should readily combine with other materials.

That material was aluminum, the third most plentiful element on the planet.

Now it’s the second most popular metal for creating things (right after steel/iron). It is so predominant that most of us use it every day without thought (and also because of smartphones and social media).

 

 

 

WHAT MAKES ALUMINUM THE CHOICE FOR SO MANY INDUSTRIES?

Aluminum offers the following properties that grant it such universal acceptance:

  • Durability — Aluminum offers a high strength to weight ratio. Hence for every unit of weight, aluminum is known to absorb nearly twice the strain/stress compared to steel.
  • Corrosion Resistant — Aluminum naturally forms an extremely thin layer of oxide by reacting with the atmospheric oxygen. The layer provides excellent corrosion protection, and is self-repairing! If damaged, the aluminum reacts to recreate it.
  • Malleability — Aluminum easily combines with other metals without reacting with them, making it a great metal for creating alloys that are stronger than it.
  • Formability — Aluminum can be molded and worked into innumerable shapes with ease. This allows aluminum sheets and foils to be easily used to a diverse range of shapes. Coupled with its inertness to corrosion, resistance to heat, and durability, aluminum has made its way into around the globe as aircrafts and automobiles, and as toasters, watches, and other household items.
  • Conductivity — Aluminum weighs half as much as copper while offering excellent conductivity for heat and electricity. Hence it has become the choice for heat sinks in electrical and electronic components, overhead wires, and within electronic circuitry.
  • Ease of recycling — Aluminum is one of the most inert metals on the planet. This property prevents it from readily and permanently bonding with other materials. This makes it easier to separate aluminum from other components, making it a highly environmental friendly metal.
  • Energy efficiency — Molding aluminum takes a significantly less amount of energy.  For example, using aluminum to replace steel in traditional vehicles is expected to saves the equivalent of 108 million barrels of crude oil in energy!

After experiencing rapid destocking in the past few years, LME aluminum stocks have been at a low level. At the end of September this year, stocks fell below 1 million tons for the first time since 2008, and began to slowly return to 1 million after mid-October. Tons above. Different from a few years ago, although the inventory is at a low level this year, the destocking speed is also moderated. From the inventory data, as of October 31, LME aluminum inventory was 1.05 million tons, which was only down from the beginning of this year. About 5%, significantly lower than the 46% and 26% slowdown in the same period of the past two years.

The main reason for the slow decline in overseas inventories is that this year’s global demand slowdown and China’s large exports have made up for some of the overseas supply gap. According to WBMS statistics, global demand in the first nine months of this year totaled 44.7 million tons, down 1.5% year-on-year. At the same time, the global aluminum supply gap also narrowed from 643,000 tons in August to 206,000 tons, while the annual supply gap in 2017 was 117.5. Ten thousand tons. Some time ago, Hydro also lowered its estimate of global aluminum demand growth in 2018. Of course, there must be a decline in China’s consumption, which accounts for 56% of global demand, but there is no doubt that consumption in overseas markets is weakening. The author believes that the slowdown in global demand is mainly due to the global macroeconomic instability and the weak global auto market.

Different from the domestic aluminum consumption structure, the automotive industry is the largest giant in aluminum consumption on a global scale. As the world’s largest auto market, China’s auto production and sales in January-October decreased by 0.4% and 0.1% respectively, showing the first negative growth this year. The negative growth for the whole year seems to be a foregone conclusion. The end of the tail has ended the “seven consecutive increases”, and Trump intends to use the knife on the import tariffs to make the US auto market worse. Recently, the US automaker GM, a large automaker, said that in response to the decline in traditional auto sales, the company was promoted. The transformation will close 7 production bases worldwide at the end of next year; while Europe is affected by the more stringent new emission test (WLTP), European car sales in September fell 24% year-on-year, although this round of sales fell sharply. The reason is that due to the new emission regulations, many unsuccessful vehicles have been banned and delayed delivery, but in the long run, car companies need to spend more money to develop new technologies to cope with higher standards. Undoubtedly will increase the production pressure of manufacturers and reduce the purchasing power of consumers, the European car market will continue to be under pressure in the next few years. The world’s top three auto markets have stalled, and the global auto market seems to have entered a cold winter.

In Japan, according to Japanese trader Marubeni, as of the end of October, aluminum stocks in Japan’s three major ports were 317,000 tons, an increase of 32% over the same period last year. Some time ago, it was also reported that some Japanese buyers agreed to raise the water price by US$103 per ton in the fourth quarter, down 22% from the previous quarter. The decline in the premium shows that the Japanese spot market is weak, and Japan is the largest aluminum importer in Asia. The country has, to a certain extent, reflected the consumption levels of other regions in Asia except China.

On the other hand, near the overseas Christmas holiday, coupled with the instability of the macro environment, many overseas traders said that their willingness to hold the spot is not large, which is another reason for the weakening demand.

Benefiting from the slowdown in demand and China’s strong exports, as of now, the spot trade premiums of the world’s major consumer destinations have fallen from the highs at the end of April, Europe, South Korea and Japan have all dropped to the lows of the year, including Europe and Japan. The high level of the month dropped by more than 50%, while the United States was limited by the impact of steel and aluminum tariffs. The spot premium was very limited, and its spot premium was still more than twice that of the beginning of the year. From the data released by LME, the LME warehouse inventory in the US only accounts for about 5.6% of the total LME inventory. Although there is a certain amount of invisible inventory in the country, as the world’s second largest aluminum consumer, the United States needs more imports. Sources of supply or restart of domestic idle capacity, but for a long time, excessive electricity costs have made local smelters uncompetitive, and steel and aluminum tariffs have increased import costs, and the continued decline in US spot premiums has been difficult.

Although global demand is slowing down, overseas supply shortages remain unchanged. According to CRU forecasts, the market deficit is expected to reach 1.77 million tons in 2018 due to continued demand growth and limited supply. Overseas markets still need more capacity to put into production, but under the current low aluminum prices, 40% of the global smelters are expected to be at a loss, which makes overseas new capacity limited, and Rusal has been affected by sanctions. Delayed the commissioning of the Taiset aluminium smelter in Siberia until 2020, and shut down the Nadvoitsky aluminium smelter in August, and recently announced that if the sanctions are not lifted, the Swedish Kubal smelter will be shut down, the smelter has been with the Nordic Power The exchange suspends trading. Although RUSAL sanctions have been repeatedly delayed, overseas traders also believe that the possibility of sanctions being lifted is too large, but according to foreign media reports, in the current situation, overseas traders are generally reluctant to hold RUSAL goods, which will surely Affecting RUSAL’s production plan for the coming year. In the future, overseas supply will remain limited, overseas inventories will continue to decline slowly, and the situation of internal tightness will continue.