The production of insulators rapidly increased in the late 1860s and 1870s, until by the 1880s most of their production consisted of glass insulators for telegraph and telephone use. The great majority of the insulators from this time period are found in a light blueish-aqua color. Brookfield was second only to the Hemingray Glass Company in the sheer number of insulators they manufactured. For a period of approximately 57 years, huge quantities of insulators marked "W.BROOKFIELD", "BROOKFIELD", and later, with just a "B", were produced. Some of the very earliest types that were made, circa 1865-1868, were evidently unmarked. Brookfield made insulators for various utility companies, and these are found with a variety of embossed names on them. Brookfield maintained business offices in Manhattan throughout most if its history, and these office addresses were embossed on many of the earlier insulators. 55 FULTON ST (1868-1882); 45 CLIFF ST (1882-1890) and 83 FULTON ST (1890-1893) are embossings found that may help date a particular example, although some molds may have been used for a time after the office changed locations. Brookfield made more than 100 different types of insulators during it's history, and some types that are illustrated in their 1912 catalog have never been found (assuming they did actually exist).
The first factory location was in the Bushwick section of Brooklyn, New York and was known as the Bushwick Glass Works throughout the early period, and evidently into the later years as well. A second glass plant was built in Old Bridge, New Jersey, and from recently discovered evidence by collector/historian Bob Stahr, that plant seems to have commenced production in about 1906. The exact time when the Brooklyn plant was closed is still open to question, but it may have been around the same time the new plant started production. Brookfield Glass Company was officially incorporated in 1898 and (again!) in 1908. I am not certain if this business name had been in use unofficially for a long period beforehand, but in any case, no insulators have been found that are marked "Bushwick Glass Works"!
Much of the later production at the New Jersey location tends toward the darker shades of aqua, "teal", and shades of dark green, including emerald and olive greens. Production of glass at Old Bridge ended in either late 1920 or early 1921 (sources of info vary) but the corporation was officially dissolved in September 1922.
Sources of information for this webpage include N.R.Woodward (The Glass Insulator in America: 1988 Report), Bob Stahr, Alice Creswick and Helen McKearin.
(Pictured: CD 102 embossed "BROOKFIELD//NEW YORK"; CD 112 embossed "B"; CD 103 embossed "B").