Shards of Indiana, Pennsylvania - A Second Look - by Jerry & Cleo Kudlac
Transparent Colored Glass Samples – Part 2
Part 2 continues with transparent yellow, green, blue and red molten glass samples that were mixed in with the glass shards. The colors yellow, green and blue are discussed together because they share some of the same colorants. Yellow and several shades of green glass could also be grouped together since they all contain high levels of uranium oxide as evidenced by a Geiger counter and a bright glow under a black light. The colors are grouped based on their predominate color when viewed under white light rather than their chemical makeup.
Yellow - Four shades of yellow (yellow to greenish-yellow) glass were found.
Yellow glass was made by the addition of uranium oxide to clear glass and was referred to as Canary (now vaseline). Depending on the conditions of manufacture and the amount of uranium used; the color can range from black, to bright yellow 7-A & B, to yellowish-green 7-C, to greenish-yellow 7-D, to olive green, to green and even red (patented in 1927). Northwood and Dugan both made canary opalescent glass, but very little canary glass was iridized. During 1897 and 1898, Northwood introduced the “Gold Rush Patterns” of “Klondyke” and the “Alaskan” in canary opalescent. Uranium oxide was also mixed with other colorants to produce various shades of green and blue transparent glass, custard glass (opaque) and opalescent glass. These will be discussed in their respective sections.
Examples shown in photo 8 are: 8-A Spanish Lace Rose Bowl in canary (cased) opalescent, 8-B Coin Spot Compote in canary opalescent and 8 – C Windflower (carnival glass marigold over vaseline). About 5 % of the Dugan/Diamond carnival glass patterns have been reported in canary/vaseline. Carnival glass patterns found in vaseline are: Adams Rib, Cherry, Cosmos Variant, Four Flowers, Target vase, Wide Rib vase and Windflower.
Green (10) – Ten different green glass samples were found.
Chrome oxide was the primary colorant used for green, but additional chemicals such as copper metal and cobalt blue were also used for a vivid green 9-A. Green could also be made using cobalt blue and uranium (yellow), possible example: 9-C. Lesser amounts of colorants resulted in various shades of green 9-B, D & E. Iron was added to make the olive green color, examples: 9 F-J. Minor chemicals such as lead, arsenic, and antimony were used to intensify the color. Uranium oxide was also present in olive green glass, examples: 9 G, H and J. Slight variations of each colorant can result in a different shade of green.
The color green (9-A) was a very popular in the early production of glass by Northwood and Dugan with patterns such as Louis XV and Cornflower (10-A) water sets, etc. About seven shades of non-iridized green water sets can be seen on pages 84 and 85 of William Heacock’s book “Dugan/Diamond – The Story of Indiana, Pennsylvania”. The popularity of colored glass waned and was replaced by other types of glass. Very little of the vivid (dark) green glass was iridized; in September, 2007, Mickey Reichel sold a dark green Farmyard bowl for $13,000. In 1928, the Diamond Glass Ware Company advertised Green Afterglow glass and Rainbow Luster. About 8% of Dugan/Diamond carnival glass patterns have been found in a light shade of green with marigold overlay. The green color varies from lime green - to olive green - to a very light pastel green.
Samples 9-C, G and J glowed bright yellow under a black light and had detectable amount of uranium by a Geiger Counter. Sample 9- C was similar in color under white and black light and uranium content as the Windflower Nappy shown in 10-B. Other examples of Carnival glass patterns in a light green are: 10-C Coin Spot Compote, 10-D Mary Ann Vase - an olive-green that glows and 10-E Question Mark Compote –a yellow green that does not glow.
Blue – Six shades of blue were found.
Cobalt oxide is considered one of the strongest colorants since it is detectable in amounts as little as 1 part in 500,000 and intense at one part in 10,000. Copper metal, lead, arsenic and uranium oxide were used as a toner to impart brilliance or subtle shades of blue, examples: (11 B-F). In 1896, Dugan developed several formulas for the “Royal Blue” (11-A) color that was used for pressed glass, casing glass and Venetian glass which had about one-half the amount of colorants as the Royal Blue, possible example 11-B. Transparent blue glass was produced by Northwood, Dugan and Diamond, but it has been reported that Diamond produced the greatest quantity of iridized blue glass. It was found that uranium was also added to blue glass. Sample 11-C glowed under a black light and the uranium was confirmed by a Geiger counter. Other variations of blue were Cerulean Blue in 1916, Harding Blue in 1921 and Vesuvius Blue in 1924.
About 36% of Dugan/Diamond carnival glass patterns are found in blue. Examples of blue glass are: 12-A Twigs vase in blue opalescent (non-iridized), 12-B Stork and Rushes mug with Lattice Band, cobalt blue, 12-C Double Stem Rose in Celeste Blue (courtesy of Jeanne and Dick Hostetler), 12-D Beaded Basket in sapphire blue (glows) and 12-E Candlestick in Harding Blue.
Red (Gold-Ruby, Selenium Ruby, and Selenium Pink)
Dugan’s gold-ruby glass formula of 1900, listed the ingredients, but not the details on how it was made. The actual process involved dissolving gold in a solution of hydrochloric and nitric acid with red iron oxide, lead, manganese, borax, antimony and tin which was then mixed into the sand batch to be melted. Patents were issued to other individuals for gold-ruby glass in 1902 and 1918. Unlike the previously described colored glass, gold-ruby glass was heat sensitive and colorless to a light-yellow when gathered from the pot. It had to be cooled and then reheated to strike the red color. Gold-ruby glass was about seven times more expensive to make than other colored glass; therefore, it was used primarily as a casing glass. Joseph Locke and E. D Libby received patents for a casing process in 1883 and 1886. Casing is when the glass-maker applied a thin layer of gold-ruby glass (or colored glass) over clear or opaque glass and formed it into the desired shape. Cased glass may have as many as four layers of glass. During the off-hand work of forming the glass, the glass cooled causing the gold to begin crystallization or dispersion. Re-heating at the proper time would develop or “strike” the red color. Cased glass may have a thin layer of red on both the inside and outside of the clear glass giving it a dark pink color which is referred to as Cranberry, (see 14-B for a side view of gold-ruby cased glass).
The first selenium red glass (13-A, B) was made by French chemist J.T. Pelouze in 1865, with patents issued in 1892 & 1894. A similar selenium ruby red glass formula was listed in Thomas Dugan’s batch book. Dugan’s formula called for iron, cadmium, sulfur and selenium which resulted in “instant color formation” upon melting (red). Appropriate annealing temperatures were required to maintain the red color. There are two kinds of selenium red glass. The second kind (formula) is known as “delayed color formation” which was heat sensitive and required reheating to strike the red color. In either case, improper handling could result in the glass being colorless, yellow, orange, sealing-wax-red or even brown. Making selenium red glass was a complex process; and as a result, additional patents for improved formulas were issued in 1934, 1940 and 1947. In 1924, Diamond Glass introduced a line of glassware with metallic iridescent tones such as the vivid iridescent Ruby Luster which is only found in candlesticks and console bowls (14-D). A process for producing a similar metallic luster (silver) on glassware was described in patents issued in 1878 and 1889.
Several pieces of gold-ruby (red cased glass) and selenium red glass (13-A & B) with yellow/orange edges were found. Selenium/cadmium red glass was also used extensively in that era (1920s) by some glass companies to make red traffic light lens. A piece of a red traffic light lens similar to the molten red glass samples was found in the shards (14-C). The glass samples edges and the lens surface both glowed to the same extent under a black light (due to the cadmium). It is not known if Diamond Glass Ware Company made traffic light lens or was it just a coincidence that ended up in the glass dump.
Selenium pink glass (13-D) contains about 1/10 the amount of selenium as the selenium red. Since early pink glass formulations were somewhat heat sensitive, the pink color can range from light to dark pink (13-C) and even a orange/pink (salmon). Diamond Glass introduced a pink glass advertised in 1928 as Pink Afterglow. To date, twenty-two different Dugan/ Diamond carnival glass patterns have been found in various shades of pink glass with a marigold overlay which is about 16% of the patterns produced.
Examples of various types of red to pink glass are: 14-A Daisy and Fern Cranberry opalescent (cased) Rose Bowl, 14-B side view of a piece of gold-ruby cased glass, 14-C Traffic light lens, 14-D Console Bowl in iridescent vivid Ruby Luster and 14-E Round Up Bowl - iridized marigold over pink glass.
Note: Selenium in smaller amounts (1/200 of the amount for selenium red) was also used as a decolorizing agent to replace manganese. A process that was first described in a patent issued in 1897.
Color Summary:
In 1900, Dugan noted the various costs of making glass in his batch book. The addition of colorants increased the clear glass costs 1.5 to 2.5 times and gold-ruby 10 times. The clear glass (least expensive) along with the popularity of the “Golden Glow Iridescence” could explain the abundance of marigold carnival glass that was made.
Why are there so many colors? The introduction of new products (colors) to increase sales/profitability and be competitive in the glass market place would be a major factor. Technically, you can state that making colored glass is a complex chemical process and any variation in temperature, oxygen, acidity, secondary chemicals and impurities during production affects the final color of the glass. But in reality, it is known only to those individuals who were skilled in the art of glass-making of that time.
The next article Non-Transparent Glass Samples will continue by covering, Opaque, Opalescent, Granite (Frit), cased glass and slag or end-of-the-day glass.