Salem, Indiana
September 1996
POLLUTION PREVENTION PROJECT (Electrostatic Spray Painting Optimization)


Child Craft Industries is a nationally recognized leader in the manufacture of quality children's furniture. The company has worked with the Indiana Pollution Prevention and Safe Materials Institute (IPPI) for several years. This project involved the optimization of the company's two electrostatic finish coating lines. The objective of the project--to maximize coating transfer efficiency from the electrostatic spray guns--resulting in reduced coating use and reduced volatile organic compound (VOC) and hazardous air pollutant (HAP) emissions to the environment.


Child Craft Industries is a recognized leader in the design, construction, and surface finish of quality children's furniture. The furniture market is a fashion-oriented business. The children's furniture segment of the market is, perhaps, the most sensitive to changes in fashion. This fact requires Child Craft's designers to be finely attuned to the market and anticipate trends, not only in design, but also in function and color schemes. Child Craft's trend-setting designs and commitment to, and reputation for, quality has contributed greatly to their success. The trend-setting designs of the furniture often require the company to employ innovative approaches and methods to achieve Child Craft's high quality surface coating standards.


Many Americans, when children, slept in a Child Craft crib. Today, the company manufactures dozens of different crib designs. Some designs receive the traditional, rich, wood stain and lacquer process, while others are coated with pigmented, pastel stains or solid colors. The finish coating production line must be flexible in its ability to handle the variations in coating requirements, yet, it must be engineered to consistently achieve high quality at demanding production rates. Child Craft innovatively addressed these demanding requirements through the use of electrostatic spray coating technology.

The wood crib is dipped in a solution which allows the wood to accept an electrostatic charge. The electrostatic spray system induces two opposite high voltage/low amperage electrical charges--one charge to the wood article to be coated (the crib), and the other charge to the paint. This process results in an electrostatic attraction between the wood and the airborne coating particles. The coating, under electrostatic attraction, is directed to the wood's surface. Additionally, the electrostatic attraction, under correct conditions, will actually cause airborne coating particles to change direction, allowing the coating to wrap onto curved surfaces. Traditional, nonelectrostatic spray systems usually achieve a 20%-30% transfer efficiency. Consequently, only 20%-30% of the material sprayed actually contacts the article. Airless electrostatic spray coating systems typically achieve a 50%-60% transfer efficiency.

Child Craft Industries is among a select few in the wood furniture industry which employs the innovative, electrostatic spray coating technology. The technology's ability to "wrap" a coating around curved surfaces makes it perfectly suited to coat the rungs and spindles of Child Craft's cribs. The challenge is to properly treat the wood so that it will consistently conduct the electrostatic charge.


The 1990 Clean Air Act Amendments (CAAA) mandates a federal air pollution permit program, which is referred to as Title V air permitting. The federal program is being phased into each state's legislation. The states will bear the responsibility of enforcing the program. Indiana has accepted the federal Title V air permit program, and permits go into effect as of December 1996. The Title V section of the CAAA regulates criteria pollutants and VOCs, while the Title III section regulates HAPs. The regulations are structured so that newly constructed air pollutant sources are subjected to more stringent air pollution emission limits than existing sources. Therefore, companies are motivated to optimize and reduce the emissions from their existing plants. This provides optimal conditions to accommodate future business growth at existing sources, without exceeding maximum threshold emission limits.

These considerations have inspired Child Craft Industries, Inc. to optimize the efficiency of its finish coating systems to limit emissions so that the company can continue to expand and also maintain its compliance with its air emission permit.


The Child Craft/IPPI team reviewed and analyzed the electrostatic painting operations in its two plants. Plant One uses a Ransburg/Devilbiss electrostatic system, and Plant Two uses a Nordson electrostatic system. The review involved trouble-shooting both electrostatic lines, including updating of the electronics, adjustment of spray pressure, optimizing spray velocity, spray-tip size, and atomization efficiency, etc. The polarity of the coating materials was also reviewed and optimized with the electronic electrostatic equipment. The object was to achieve a 15%-20% improvement in the process.


The Child Craft/IPPI team reanalyzed the electrostatic process after the completion of the optimization project. The team found that the project's objectives were met and that the transfer of sprayed coating to the wood crib did, indeed, increase. The team found that electrostatic coating use and, thus, emissions had been reduced approximately 17%. This decrease resulted in an annual, VOC/HAP emission reduction of 2.5 tons and a raw material cost savings of $10,000 per year.


It is important to understand that this P2 project involved the optimization of an existing, innovative, extremely efficient, coating method which, in and of itself, exemplifies pollution prevention.

This optimization project increased the performance of the electrostatic system by extracting (from an already productive process) an additional, yearly reduction of 2.5 tons of VOC/HAP emissions and $10,000 in savings.

Child Craft Industries exhibited great foresight by investing in electrostatic coating technology. Electrostatically sprayed coatings improve productivity, reduce coating use, reduce VOC/HAP emissions, and save money.

1 (c) Purdue University Research Foundation, 1996