Volume 34, Number 3, March 1999

Mirrors for the New Millennium

by Joy Manna

What awaits the mirror industry in the new millennium? Unfortunately, none of us have the benefit of consulting a magic mirror for our answers, but one truth is apparent. Today as never before, we are faced with intensified competition from an increasingly global market. Mirror manufacturers who form partnerships with their chemical and paint suppliers are able to respond quickly to the rapidly changing needs and demands of the global marketplace. Astute industry insiders must consider ways in which they can improve products and/or processes to ensure future success. Where will these improvements emerge and who will be driving them? Some of these improvements will be environmentally driven, while others will be created by those mirror manufacturers and coatings suppliers with the resources and technical expertise to deliver products that will leapfrog current technology and quality.

Technological Improvements

As this century draws to a close, we note that the chemistry of mirror manufacturing has made remarkable improvements in the areas of quality and production efficiency. During the past 20 years, mirror production has seen the process grow from air spray techniques with poor application controls to high-speed curtain coating systems with precision control of the applied paint film. Likewise, today’s airless spray systems have high efficiency, improved chemical knowledge and proper engineering that allowed the industry to control and monitor the deposition rates of silver and copper films.

Strides are being made right now for further improvements. A new technology has emerged that expends significantly less pollution than current manufacturing processes utilizing copper film by providing a mirror with enhanced performance and added value by dramatically reducing black-edge corrosion. This process replaces the copper film coating that has long been associated with mirror manufacturing. In fact, as of its introduction in 1995, this process has been overwhelmingly accepted as the new quality standard throughout Europe. Our company is introducing a patented process this spring—Silver Seal. We developed this process because of several identified key benefits that make this not simply another product, but a significant leap in technology and the process of mirror manufacturing.

Eliminating Copper Film

Deposition of copper over silver film has always been a necessary step, but there are a number of problems associated with this chemistry. First, the elimination of copper film in today’s mirror manufacturing process improves the quality and life expectancy of a mirror. The use of a copper film, layered between a silver film and paint film, develops a reactive galvanic cell that may cause the silver film to degrade quickly when subjected to ammoniated cleaners and water. The literature on the care and installation of mirrors published by the North American Association of Mirror Manufacturers clearly warns not to use ammoniated glass cleaners to clean a mirror. The ammonia dissolves the copper film easily, causing the paint to delaminate and shortly thereafter, the mirror darkens forming black edges.

Pollution Due to Copper Film Use

Secondly, there is a pollution problem associated with the use of copper. Abundant quantities of pure water need to be used in this process, especially in the rinsing and removal of iron or zinc which manifests when the copper film is applied. The high copper concentration and acidic pH of this waste effluent stream require a high degree of engineering controls to reduce the copper in the stream to acceptable levels. Today, many mirror manufacturers need to achieve a copper level below one milligram per liter and a neutral pH within their stream. Controlling this system, analyzing the waste stream daily to avoid costly fines, maintaining the necessary equipment and dealing with copper sludge continues to be a major issue and investment for most mirror manufacturers.

Copper Film Reduces Silver Adhesion

Finally, the galvanic system of depositing a copper film reduces the adhesion of the silver film from the glass substrate. Up until now this has been unavoidable because the protective paint film needs copper in order to achieve total adhesion. Without a copper barrier coat, the paint film will adhere poorly to the silver film exponentially increasing the occurrence of black-edge corrosion of the mirror.

The new copper-free process does not adversely affect the silver to glass adhesion. It also provides an inert barrier film that chemically protects the silver film and adds to the protective properties of the paint film. This new process technology opens the door for future paint improvements as well. There are a number of paint issues that are environmentally-driven (see page 90) which measure the lead content that may be released from mirror scrap. The new copper-free process technology encompasses various paint products that meet the demands of these environmental issues, while at the same time enhancing the quality and durability of mirrors.

Joy Manna is marketing director for the composites and glass coatings strategic business unit of Lilly Industries Inc., of Rocky Hill, CT.

 

Defining Characteristics

Toxic Characteristic Leaching Process

An Environmental Protection Agency (EPA) test that determines the amount of a toxic heavy metal chemical that might be leaked out of the waste material if this waste was placed in a public landfill. Based on this test result, a waste will be classified as a hazardous waste if it exceeds the established limits and disposal is restricted.

Volatile Organic Compounds

A group of chemicals that react in the atmosphere with nitrogen oxides in the presence of heat and sunlight to form ozone. This does not include methane and other compounds determined by the EPA to have negligible photochemical reactivity. Examples of VOCs include gasoline fumes and oil-based paints.

Hazardous Air Pollution Substances

Any of those chemicals listed by the EPA as being hazardous when released into the air.

 


USG

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