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Opaque Colors


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I asked David Allaway, a marble collector and amateur glass historian, these questions.

His detailed answer is below.(with his permission)

Hi David,
Where can I find verification about the German opaque colors (other than white or yellow) being post 1900?
Also, do you know the component of glass that makes it opaque?
There's been some discussion about the black lined color splotches on the brightly colored German clowns being a reaction of the color with selenium in white glass.
I don’t have any references, just personal observation. From the beginning of my marble collecting, I always noted that most antique glass marbles have only opaque white and opaque yellow. These are cleverly combined with transparent red, transparent blue and transparent green. The threads in threaded glass marbles are opaque white and opaque yellow, and sometimes these are overlaid with transparent red, transparent blue, or transparent green. Similarly, the cores of divided-core or solid-core marbles are opaque white or opaque yellow, or both, often overlaid with transparent red, transparent blue, and/or transparent green. The same is also true of “Onionskins” which have a base coating of opaque white or opaque yellow, or segments of each, with an overlay of chunks or streaks of transparent red, transparent blue, and/or transparent green. These are what I think of as “classic” transparent swirls and onionskins, and comprise the vast majority of antique handmade glass marbles. This includes most large swirls and examples with ground (faceted) pontils, and can be classified as early-mid period.
The exceptions to the above, using collector names, are the so-called “Bristol” or “English swirls”, “Lutz” marbles, and opaque marbles including “Opaques”, “Indians” and “Clambroths.” These have a wider variety of opaque colors (red-orange, turquoise, pale green, etc.) which are unknown in earlier swirl marbles. From catalogs, the Lutz marbles date to approximately 1910-1914. The so-called English swirls, in addition to their vivid opaque colors, are noted for the clarity of the glass, and lack of impurities. This would be the result of more modern furnaces using natural gas, or recirculating coal gas, as opposed to wood-fired or less-sophisticated coal furnaces. The newer furnaces, increasingly in use after 1900, would produce much higher temperatures, and would force bubbles and impurities from the glass, and introduce less soot and ash, resulting in much clearer glass. The clearer glass, and the use of opaque colors other than white and yellow, seem to go hand-in-hand. I believe that the “English” swirls were produced in Germany, but dominated the English retail market post-World War I, after the U.S. had largely converted to domestically-produced machine-made marbles. I would classify those marbles using a variety of opaque colors, and impurity-free transparent glass, as being late-period.
The primary ions used to produce opaque glass are: Tin, Antimony, or Arsenic. Looking at the periodic table, Germanium might have worked as well, but was undoubtedly too rare and expensive.
An intriguing question is where the colored glass came from. Because it was mostly in threads, it is possible that they were imported from Venice, as it still is. A clue can be seen in close examination of Lutz marbles, where the bands are composed of two or more individual threads. The colored solid cores are composed of multiple rows of colored threads, giving a washboard appearance. It is possible that the introduction of clearer base glass (locally-produced) occurred in the same general time frame as the availability of a wider variety of opaque colored rods. The uniformity of the opaque colors seen in Lutz, Indian and Clambroth marbles, for example, would indicate that these colors were not locally-made in random batches, but were sourced from a wholesale supplier of opaque glass rods, with standard catalog colors, and subject to good quality control.
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Interesting. The opaque yellow in 'old' handmades is a Naples Yellow or lead antimonate yellow. Other possible opacifiers include lead arsenate and calcium phosphate / bone ash. The transparent red used in 'old' handmades is gold ruby. Think red stripes on peppermint swirls. The gold based color pallet is so distinct compared to selenium and copper.

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For some reason I thought old handmade swirls/onionskins COULD have opaque green blues and reds (almost an oxblood red), which was an indication they were from the earlier part of the handmade period and not later? Probably semantics (or exceptions to the rule) and not to dispute the info above which is very interesting by the way.

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Those almost look modern

I'd wager a CAC it isn't.:)

The German's used opaque glass before the 'Bristol/English' handmades (argued to be from the later end of the German handmade era).

I believe they could and did, some of the best examples most often seen in the single pontil hand gathered marbles that many used to think were Leighton transitionals ie: oxblood, eggyolk etc.

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You are correct, The early German opaque colors were not very bright colors, dull and earthy except for the lapis blue. I've always called it opaque cobalt LOL. notice the white does not react with the yellow or red.

Kind of strange, all those bright colored "English types" seem to be in such good condition, also as of late their available quantities seem to outnumber the old ones.

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