If you have journeyed along Lake Michigan through Chicago's North Shore suburbs, you could not have missed seeing the awesomely beautiful Baha'i Temple, symbol of hope for a united and peaceful world. Often called the "Taj Mahal of the West," the nine-sided structure forms a temple of light- sunlight streaming into its interior by day and temple lights glowing through the dome by night. The jewel-like building, known as the House of Worship, is recapturing the original radiance it displayed earlier in the century. The Baha'i Temple began to "take a bath" last fall to restore its natural pure whiteness. Traditional methods of cleaning concrete, such as sandblasting and acid applications, proved to be erosive to the unique design and delicate surface of the temple. What was finally used was a special solution blended of 23 components developed by a Montreal laboratory. According to the building superintendent, the ingenious method of applying this secret solution, called RC-3, is the key to the cleaning project. No harm is done to the structure as a 600 pound pressure jetstream quickly neutralizes whatever acid is contained in the solution. After the structure is cleaned, a clear water-repellent coating is applied. This protects the exposed aggregate and smooth concrete surfaces against such elements as ultraviolet rays from the sun, dirt, soot and other atmospheric and industrial pollutants. Officials of the Baha'i Temple selected a coating based on a methyl methacrylate formulation, which, they feel, will provide the best protection on the temple's exposed aggregate surfaces.