Michelle S. Lee
13 March 2014
The Life Cycle of Mirrors: The Materials
The invention of mirrors resulted from the human fascination of reflections thousands of years ago. Modern mirrors are coated, reflective surfaces made from both glass and metals. The earliest mirrors, however, were made of black volcanic obsidian, eight thousand years ago in Anatolia, present-day Turkey. Since then, the Ancient Egyptians began the use of polished metals such as copper into the production of round, ornamental mirrors for the upper class. As civilizations discovered methods of producing metal alloys and blowing glass, mirror production continued to revolutionize into the modern glass mirror. The Romans engaged in glass fabrication for manufacturing mirrors in the first century AD in which lead was employed as the reflective coating. In the middle ages, mirrors simply consisted of convex metal disks of bronze, tin, and silver with glass in which major influences came from the Venetians who were known for their techniques in glasswork. From then on, the process of producing the highly reflective material diffused across various regions to which a German chemist is credited today with the formulation of the modern mirror, a method in which contemporary factories have adopted (“History” 1-7).
Mirrors have a wide range of purposes varying from functioning as a household gadget to their applications in scientific experiment and observations. Materials invested into fabrication of mirrors and processes can be altered for the purpose the mirror serves. However, in the consideration of the household mirror, the basic elements of mirror production today remain the same despite its purpose. Rather, one must consider the contemporary technology has allowed us to utilize more resources in our favor to mass-produce mirrors for decoration, an idea that dates back several millennia ago.
The full life cycle of mirrors consists of the gathering of raw materials and the transportation of them to factories that produce glass. Because glass is the capital material in the production of mirrors, the full cycle must take into consideration the production of glass, which is a secondary material. Following the cycle, mirror manufacturing takes place. The final component of the life cycle is the reduction of the mirror as waste. The waste management is not that of an effective one, since the mirror, through its various processes, contains too many chemicals to be deemed as glass and recycled, which results in landfill waste. Energy, emission, and byproducts complement the full life cycle and are considered as well.
Glass is a secondary material in the overall process of producing mirrors. Known for its transparency, rigidity, ability to be polished, and its simple production, glass consists of sixty percent silica, otherwise known as sand, soda ash, dolomite, limestone and broken glass, termed cutlets. Silica is obtained through mining or refined from sand and it exists abundantly in nature as quartz. Locations of silica mining takes place in the northern portion of the United States, such as Minnesota and Wisconsin and also in other various parts of the world. Silica has the ability to be produced synthetically and has been a chemical compound known for centuries. Limestone consists of calcium carbonate, in which is used in the refinement of glass, and is found in the form of remains of plant organisms and as rocks in caves. Dolomite holds similar properties as limestone; it is a mineral that consists of carbonate, calcium, and magnesium. The addition of glass cutlets supplements the production process and could be obtained from glass trimmings produced in the end process. Other primary materials, or materials derived from nature, include metals such as tin, silver, and copper which would in end serve as part of the reflective material in mirrors. These are obtained through mining and the creation of metal alloys. In the acquisition of primary raw materials, the use of fossil fuels plays a significant role in mining, refining, and transporting (“Emissions Estimation”10).
After the acquisition of the raw materials and glass cutlets necessary in the production of glass, these materials are grinded in a grinder to produce float glass, a type of flat glass known for its smooth surface. Its high quality serves many purposes for both household and industrial uses. Float glass begins with the melting of silica, sand, soda ash, cutlets, limestone, and dolomite. The silica is known as the “former” for its importance in the formation of glass whereas soda ash and glass shards are known as the “flux” due to their ability to lower the amount of energy required to melt the silica to form glass. Finally, the limestone and dolomite are known as the “stabilizer” for its properties of polishing and increasing the strength and stability of glass. The melting process includes the use of natural gas and superheated air in a tank furnace that reaches 2900 Fahrenheit. Limestone is the final addition for a strong finish of the glass. At this moment, the molten glass leaves the furnace and pours onto a layer of molten tin in a form of a ribbon at about 1100 Fahrenheit. The flat glass is called the glass ribbon. On a flat conveyor belt, which in turn is powered by electricity, the glass perfectly paralleled the ground surface and becomes evenly spread out to a desired thickness over tin. Tin helps retain the liquid glass by refraining the glass from spreading thinner. The addition of hydrogen and nitrogen in the atmosphere prevents the tin from oxidizing. Next, the glass undergoes the annealing process where it is cooled to prevent damage from cracking until the temperature reaches 200 Fahrenheit (Figure 1). The glass continues to be run on a conveyor belt in which the edges are trimmed, perfected, and finally, inspected for defects (Figure 2). As the glass gets trimmed, the leftover shards are reused in the process of making glass for reducing the amount of energy required to melt silica. Finally, the glass is finished off with the application of protective powder transported to factories specializing in mirrors (GANA) (“Emissions Estimation” 4-10) (Glass 4).
With the acquisition of the glass, the process of mirror making begins. First and foremost the glass is placed onto a conveyor belt, powered by electricity, to be cleaned off from any residue and contaminants such as oils. Excess residue will influence the final quality of the mirror. Polishing includes the use of cerium oxide, a chemical known for its ability to polish, and hot deionized water is used for rinsing to prevent any leftover minerals that may react with metals (How It’s Made) (Patent).
The remaining process includes the plating of metal silver back that serves as the reflective material, a process that transform glass to a mirror. However, the chemical properties of silver does not allow it to adhere to the glass and therefore, tin, is applied first. Liquefied tin is poured onto the cleaned glass to serve as adhesion. Next the liquid form of silver, with the addition of a chemical activator, is poured onto the back of the glass, on top of the tin layer. The addition of the activator allows the silver to adhere to the tin. Excess silver from this step is rinsed off, filtered, and reused again later. At this point, as part of the final quality, another metal must be added to protect the silver metal that serves as the reflective material. The use of copper accomplishes this purpose well. Copper is sprayed onto the backside of the mirror on top of the silver to protect the reflective material because paint itself will not be sufficient. The excess copper is rinsed off and the product is run through heat to vaporize any moisture before the final step, the addition of paint. The first layer of paint is then added to the dry mirror. Once again, the mirror is heated of 160 F again to cure the paint, in which after, the second layer of paint is added and this time, the mirror is run an even higher temperature of 210 degrees Fahrenheit. The paint used in this process consists of polymers, carbon, lead, and various heavy metals. Finally, the finished product is inspected for defects from manufacture. When the process of mirror fabrication is finished, the mirrors can be cut or shipped elsewhere to be fashioned for décor (Figure 3) (“How It’s Made”) (Patent).
Considering the entirety of the process of gathering materials, producing glass, and finally, producing mirrors, a crucial aspect to consider is the impeccable amount of energy required. Much of this energy is in the form of heat and derived from fossil fuels such as petroleum derived from natural resources from underground and offshore drilling. Additionally, mining requires energy for gathering vast amounts of materials from the natural environment. The transportation methods include land, air, and water depending on the origins of the materials, but all accounts would require fossil fuels. Finally the entire production process requires vast amounts of heat to maintain furnace temperature and vaporize water in the addition of metals and paint onto the mirror.
This energy intake is not without consequences due to the material consumed. Three categories of emissions should be taken into consideration: the handling of raw materials and production, the pollution from energy, materials, and waste, and the maintenance of production and waste management plants (“Emissions Estimation” 9). The emissions begin at the extraction of raw materials through mining. This process impacts the environment ecologically and requires fossil fuels for both the extraction and transportation of materials to glassmaking plants. The handling of both primary and secondary materials involved in the production of mirrors include the melting of silica and materials in glass, the formation of the mirror from glass and application of metals and paint, a secondary material, and the finishing steps of the manufacturing process. The process of glass production, specifically the melting heating of carbonates, results in emission of carbon dioxide (“Emissions Estimation” 4).
There are also manufacturing byproducts that result from inputs of raw material. Glass production results in the emission of fluoride particulates, sulfur dioxide, nitrogen oxides, carbon monoxide and various solvents through vents or open vessels in a factory. These pollutants spread into the atmosphere, water, and land. In the production of mirrors, the byproducts include metallic oxides that derive from the application of various metals such as tin and silver to the back of the mirror (“Emissions Estimation” 10).
Because mirror made with glass and a metallic reflective material, they cannot be recycled with glass. Glass itself is a highly upcyclable material, lasting for nearly three thousand years and reserving the same quality each time. However, mirrors are a different matter. The main method of recycling is simply to reuse the material for another purpose, such as crafts and refurbishing to create something else such as a portable mirror (Figure 4). Most of the time, these household mirrors will not be accepted by recycling centers and must be treated in a different way (“Recycling Mirrors”). The mixture of contaminants of glass, such as the reflective exterior will degrade the glass in the recycling process and pose a threat to the equipment. Only a few places accept mirrors and they are recycled to make fiberglass and glass for decorative purposes.
The overall full life cycle of mirrors begins at the acquisition of raw materials and ends with the mirror. Mirrors consist of chemically treated glass and contain several other metals that make mirrors unrecyclable. This shows mirrors consume a lot of energy in the production, emit byproducts, and result in as significant waste because energy and resources cannot be extracted from it to be allocated elsewhere. The end life would be in the landfill. In addition, mirrors would take a million years to degrade due to the upcyclable property of glass.
Therefore, taking into the consideration of the materials put into the production of mirrors, designers may consider resorting to find alternative ways to produce household mirrors that reduce the amount of waste produced and energy consumed. One way this could be accomplished is by differing the materials that lead to better recycling and overall waste management. This could include the production of a mirror whose recyclable glass could be separated from the metal and therefore, both the glass and metals could be recycled. This would result in a more efficient use of energy and overall more productive life cycle of an object that reduce the impact on the environment and result less consumption of non-renewable energy.
In the process of researching the materials involved in the production of glass, there were difficulties distinguishing what kind of glass are used in mirror due to the various types of chemical changes that could be made to better suit the purpose of the glass. Therefore, in the research of mirror production, we concluded the most plausible type of glass involved in mirror production is float glass, which is a type of flat glass. However, the basic steps involved in glass making are the same, as they have been for thousands of years. Some more difficulty was encountered in the research of waste management of mirrors. Glass is known for its upcyclability but mirrors contain other metallic elements that would affect the recycling process. Therefore, methods involving the use of mirrors after it has become waste are not well documented, but the byproducts and emissions of the process are. After researching the entirety of the production, many resources were not directly relatable to mirrors, but rather required us to compile an overall process that included the manufacturing of glass before mirrors.
Glass. Rep. United States Environmental Protection Agency, Feb. 2012. Web. 11 Mar. 2014
This source is especially valuable because it contains information on the acquisition of raw materials and manufacturing. Not only does it provide information on what raw materials are used in the production of glass, it also includes numerical data involving the use of materials and its emissions. This source also provides information about recycling and emission factors.
Emissions Estimation Technique Manual for Glass and Glass Fibre Manufacturing. Manual. National Pollutant
Inventory, Aug. 1998. Web. 11 Mar. 2014
This source highlights the process of glassmaking and its materials. The process is described and different diagrams are used to clarify the process of making glass. This source includes the emissions and byproducts of this process by the handing of materials, facilities, and processes.
"GANA Videos: Float Glass Manufacturing Process." GANA Videos: Float Glass Manufacturing Process. N.p.,
n.d. Web. 11 Mar. 2014. http://www.glasswebsite.com/video/fgmd.asp
From the Glass Association of North America, this video describes the process of producing float glass, a type of flat glass, beginning with the raw materials involved. However, this source does not describe the energy involved in the process nor does it comment on energy emissions.
"How It's Made Mirrors." YouTube. YouTube, 22 Apr. 2010. Web. 11 Mar. 2014.
This source derives from a television show that specializes in documenting how everyday items are made. They provide an easy to understand method and explain the production of mirrors with the adhesion of various layers to finalize glass into a reflective material. Additionally, the patent addresses the various sources of partic
Czanderna, Alvin W., Pitts, John R., Thomas, Terence M. “Method of bonding silver to glass and mirrors
produced according to this method” US Patent 4547432A. Web. 13 March 2014.
This patent describes the method in which silver is added to a piece of glass to serve as the reflective material. The patent includes various metals that are involved in the adhesion of silver and the particulates released. Though this source describes a method slightly varying from that we describe, much of the details remain the same regarding the materials used in producing mirrors.
"The History of Mirrors and Mirror Facts." Invention of the Mirrors and Its Origins. N.p., n.d. Web. 11 Mar. 2014
This website provides the history of mirrors from its beginnings to contemporary times. Additionally, this site includes information on how mirrors are made and is a good starting point in beginning to understand the process of mirror production and its revolution.
"Are Mirrors Recyclable?" Can You Recycle Mirrors? N.p., n.d. Web. 13 Mar. 2014.
“Keen for Green” gives a direct answer as to whether or not mirrors are recyclable and why they are not.
"Recycling Mirrors." Recycle San Diego. N.p., n.d. Web. 13 Mar. 2014.
Because mirrors require special treatment in recycling, this source states how and methods of recycling and refurbishing mirrors to reduce waste. Mirrors can be given to special centers that accept glass parts. This source states that mirror recycling requires special treatment centers.
Clarise De Borja
13 March 2014
Embodied Energy in Mirrors
Before the need to make a mirror, pools of water were used as a natural way to view ones reflection (Enoch 1). Then, a rock or clay bowl was used as a way to make the pool portable (History 1). Later, highly polished obsidian volcanic rock was used to provide a mirror image (Enoch 1). Afterwards, the Egyptians used various sheets of metals to create reflective surfaces used as mirrors (Enoch 2). They were curved and highly polished brass or bronze as an example (Made). In Sidon, metal coated glass mirrors were first discovered (History 2). The Romans fabricated a technique using blown glass with molten lead (History 2). The Renaissance brought the use of tin-mercury amalgam to coat the glass for mirrors (History 3). Then, by the seventh century, mirrors and their frames increased in importance to home decoration with first Venice and then London and Paris producing them (History 3). Later, in the 1800s, Justus von Liebig invented the method of coating glass with silver (History 7). His methods shaped modern day affordable mirror manufacturing by using silver’s nature of chemically reducing to adhere to glass in a line layer (History 7).
Due to the accessibility of materials, hand mirrors came before larger full-body mirrors until the ability to produce a large enough reflective area. Thus, materials used in the creation of a mirror changed with the availability of resources at the time. Along with the change in materials, the size of production increased as energy sources with higher densities were discovered. In modern day, mirror production has become commercial industry from mining of the raw materials, float glass manufacturing, manufacturing of the mirror, and repurposing mainly running on fossil fuels.
Mining is used in the acquisition of raw materials used in the production of mirrors. Even though the raw materials can be mined from around the globe, in looking at the energy costs, the United States will act as the sample of study. The United States is the leading producer of soda ash and the second-largest in copper (BCS 6-9). Soda ash comes from Wyoming, California, and Colorado (BCS 11). Copper comes from Arizona, Utah, New Mexico, and Montana (BCS 12). Silver comes from Nevada, Alaska, Idaho, Arizona, and Utah (BCS 12). Limestone and dolomite come as crushed rock from Texas, Florida, Illinois, and so on (BCS 12). Silica comes as sand from Minnesota, Wisconsin, Iowa, and Illinois (Richards 1). However, Tin (as an ore cassiterite) is not mined in the United States but instead from China, Malaysia, Australia, and so on (Tin 3).
In order to excavate the materials, many types of energy and machines are used. For instance, industrial drills, equipment, explosives, blasting agents, and oxidizers are ways of extracting (BCS 14). Then, commercial grade trucks are used to haul the materials not their next destination. Heavy-duty commercial grade drills and equipment run on petroleum based fossil fuels. The explosives, blasting agents, and oxidizers comprise of fuel oil mixtures, emulsions, and so on (BCS 14). In quarrying, nonmetal, and metal mining, about two trillion British thermal unit (1 Btu equals about 1055 Joules) of explosives, blasting agents, and oxidizers were used (BCS 16). The energy requirement to run the United States mining operations is about 1.125 quadrillion Btu (BCS 16). The refinement stage alone accounts for about two-thirds of the energy needs (BCS 18). Refinement also produces pollutants that get released into the atmosphere.
Additionally, before any materials can be extracted from the earth, the site for mining needs to be prepared (BCS 18). The use of fossil fuels is needed in drilling and transportation either to run the machines directly or provide electricity (BCS 18). In total, the extraction, refinement, and transportation use about 68.6 trillion Btu for soda ash, pot ash, and borate; 46.6 trillion Btu for copper and nickel; 0.6 trillion Btu for silver; 47.8 trillion Btu for crushed rock (including limestone and dolomite) (BCS 19). This is a total of 163.6 trillion Btu used in the entire process of mining the raw materials for mirror production, with the exception of tin, in the United States alone. Then looking at the global perspective of mining as a whole, the energy use is an astonishing amount that numbers cannot provide an accurate perspective. Also, the burning of all the fossil fuels and explosives causes carbon dioxide emissions.
The production of float glass includes the mined raw materials of silica, limestone, soda ash, dolomite, and glass culets (which are remaining glass pieces from past productions). Silica is the primary base for the glass plate making up about sixty percent of the batch (Float). Limestone and dolomite are used to strengthen the glass (Float). These materials are called stabilizers (Energetics 36). Soda ash and glass cutlets are used to lower the temperature and energy needed and quicken the melting process in the furnace (Float). These materials are called fluxes (Energetics 36). In preparing this batch per ton of glass made, the amount of energy used is about 1.2 million Btu (Energetics 27). All the materials are then poured into a 2900 degrees Fahrenheit furnace to be mixed and melted (Float). To run this furnace, natural gas and super heated air are needed to be able to reach that high of a temperature. In the melting and refining phase, about 8.8 million Btu are used per ton of glass (Energetics 27). After heating up in the furnace, the liquid glass (or the ribbon) is poured out into a layer of tin, which is higher in density than the ribbon (Float). This layer of tin always the glass to be thick since it prevents the liquid glass from spreading out too much due to acting has a mold for the glass to follow (Float). To thin out the ribbon, rollers are used to gently stretch it out (Float). The forming of the glass takes about 1.5 million Btu per ton of glass (Energetics 27). After the tin bath, the ribbon is placed into the annealing layer where it hardens (Float). The amount of energy required in the post forming phase uses about 4.2 million Btu (Energetics 27). The ribbon is slowly cooled and then cut to remove the uneven edge and to ordered size (Float). The finished glass ribbon is coated in a protective powder and shipped to its next destination (Float). Throughout the whole production process, the ribbon and then finished glass are moved by rollers, automotive conveyer belts, and robot arms (Float). Electricity is used to power these machines. However, electricity is a secondary form of energy. Fossil fuels are ultimately burned to create electricity unless the plant uses alternative forms of energy, such as hydropower, solar, or wind. Additionally, the transportation uses refined petroleum to power the specially equipped trucks and ships to move the glass to its new destination domestically and globally (Float).
One of the places that the produced float glass can end up is a mirror manufacturing plant. The glass is laid out on a conveyer belt and taken to the washing station where sprayers shoot a solution of water and cerium oxide at it (TRR59). Brushes polish the top and bottom to remove any oils and contaminants (TRR59). Another set of sprayers shoot very hot demineralized water at the washed glass to rinse (TRR59). Demineralized water is used since the minerals and ions found in regular tap water would damage the metals put on the glass (TRR59). First, liquefied tin is sprayed on to the back as an agent for the silver to adhere to since silver cannot chemically bond to glass (TRR59). Second, liquefied silver and chemical activator solution is sprayed on top of the tin (TRR59). The silver layer hardens immediately after interacting with the tin (TRR59). Silver is the main component that gives clear glass a reflective coating, which makes a mirror (TRR59). Sprayers of demineralized water rinse off the excess silver that is recycled back into the system (TRR59). The silver layer is protected by a layer of liquefied copper that is sprayed on next (TRR59). Another set of sprayers rinse off the excess copper with demineralized water (TRR59). The glass with multiple metal layers is passed through a dryer that is about 160 degrees Fahrenheit evaporating the leftover moisture on the surface (TRR59). Next, the panel passes through one paint coater copper side up and through an oven that is heated to 210 degrees Fahrenheit, which cures the paint layer (TRR59). Then, the panel passes through another paint coater and is cured for a longer time and at a higher temperature, which is about 245 degrees Fahrenheit (TRR59). The finished mirror passes through a final acid wash to remove any remaining metal residues (TRR59). The mirror is then inspected, cut to desired size and shape, and transported to its next destination (TRR59). To make a beveled edge, the beveling machine first cuts the edge and polishes with concentration cerium oxide (TRR59). Similar to glass production, the panel of glass is run on conveyer belts to undergo the layering process to be become a mirror. These conveyer belts are also powered by electricity, which is a secondary energy source originally fueled by the burning of fossil fuels. The scouring and beveling machines that cut, bevel, and polish the mirrors also run on electricity. However, the production plant could be using alternative energy sources to get electricity. For the ovens used in the curing process and the heating of the demineralized water, natural gas and fossil fuels are used to reach the high degree of heat. For the transportation with trucks and ships, refines petroleum is burned to send the mirrors domestically and globally.
After the mirror has been sent to its new destination and enjoyed for many years, it either gets broken or the owner wants to switch it out. However, there is a problem with throwing away the mirror. For instance, plain glass is able to be recycled and its purity and quality will not degrade over time (Glass 1). The reason for this is that glass itself is used in the production of more glass (Glass 2). Thus, the difference between plain glass and mirrors is that mirrors are chemically treated; therefore, this makes mirrors difficult to recycle (Are 1). This difficulty is due to the multiple layers of tin, silver, copper, and paint that need to be stripped away before glass recycling could even happen and very few centers take them (Are 1). Thus, the best way to “recycle” a mirror is by repurposing it. For example, one could give the old or broken mirror to a refurbishing center to extend its life for a new owner. Another way is that the owner can keep the mirror and use it in crafting or reframe it. However, repurposing also requires the burning of more fossils fuels to create something new from the mirror. This differs from recycling because in the recycling process the materials and energy are able to go back to same production line that it was created from and make more of the same item instead of creating a completely new product that may not be in as high demand. On the other hand, despite a mirror’s ability to be repurposed, it will eventually end up in a landfill. This outcome leads to a glass mirror sitting in an overfilled landfill until the glass itself will biodegrade in the next million years that is not taking into account the chemical layers stuck to the glass.
The ultimate outcome of the glass mirror sitting in a landfill for millions of years until it eventually will degrade back into the earth shows that all the energy put into creating the mirror just ends up being wasted. The reason for this is that trillions of Btu is put into producing a product that cannot even be completely recycled for another use. Thus, just as the product made with energy becomes waste, the energy used in its production also lost. Furthermore, more mirrors need to be made to meet the demand for the use in bathrooms, decorating, and buildings since mirrors themselves cannot be recycled. This process shows that there is a never ending cycle of waste. With the earth reaching its capacity in providing for overpopulation and their energy demands, there needs to be a change in the process of manufacturing this product. Mirrors need to become more able to be recycled. So, all the energy and materials that go into the production of a mirror go to waste since there is not infinite supply of fossil fuels and natural gas to power machines and vehicles and raw materials.
From an energy standpoint, the production of mirrors is wasteful. There is a large amount of fossil fuels and natural gas being burned in the mining of raw materials, float glass manufacturing, manufacturing of the mirror, and repurposing. In an effort to combat the massive energy waste and materials, it would be beneficial to rethink the manufacturing process to invent a more sustainable design for the mirror. So, humanity can continue to stare at their reflection and appreciate the allusion mirrors give to enlarge a small room with a more lasting product.
In research this topic, it was shown that not all the details on a product have been published or shared with the public. Thus, the assumption of local mining is similar to global mining and most machinery was run by fossil fuels. Furthermore, some of the information would be publish, but pieces would be withheld, such as looking up an estimate of fuel oil consumed in the extraction of soda ash from Energy and Environmental Profile of the U.S. Mining Industry. Additionally, there was a difficulty in find information just on mirrors. The topic had to be broadened to include the manufacturing of glass, which is a major part of the mirror, since there was more information available on glass than mirrors. The lack of information on a particular product of mirrors proves that consumers are left blindsided in knowing the all factors of the products, which they invest in. The privatization of certain information on products may be there to protect the profit of the manufactures and business that work with the products. However, consumers should not have information withheld from them. There should be transparency between the producer and consumer, in which it is the consumer’s right to make a decision on his terms will all the options and their histories laid out in the open.
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Enoch, Jay M. OD, PhD, FAAO. “Historical Perspective: History of Mirrors Dating Back 8000
Years.” Optometry & Vision Science. 83.10. (2006): 775-781. Print.
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