Greg Merkel, research fellow at Corning Incorporated answers the question of the difference between Royal Purple and amethyst.

Good question! And not a simple answer. But fortunately (and contrary to the assumptions of some) research continues to be conducted into Steuben’s colored transparent glass, with the hope of being able to make statements based upon facts rather than long-held opinions. Here is what can be said at this point, based upon records written in Carder’s hand:

Royal Purple contains manganese oxide as the sole colorant, as do the colors listed as Pale Purple, Light Purple, and Pale Amethyst, the latter three having lower amounts of manganese. The color listed as Amethyst actually has two identities. In some batch formulas, Amethyst, like Royal Purple, is colored by manganese, but in even higher amounts. I think that the formulas for manganese-Amethyst disappear at about the time the first formulas for Royal Purple show up, and I suspect (opinion, not fact) that the name may have been changed from one to the other coincident with the reduction in manganese.

In other batch formulas, Amethyst is found to be colored by gold (red) + cobalt (blue), not by manganese (although there is a small amount of manganese in the batch, it is there to help promote the formation of the gold crystals, as are the small additions of antimony and tin oxides). Often, but by no means always, these formulas go by the extended name “Amethyst Ruby” because they contain this gold ruby component and were “struck” by reheating in the same manner as a gold ruby glass.

From my limited experience, it appears to me that Royal Purple was used as “solid” objects or components of objects, commonly optically ribbed. From what I can tell, Amethyst Ruby was used as a casing on crystal, such as perfume bottles and engraved plates and stemware, and also in Matsunoke decorations. Royal Purple tends to be a darker, less “pure” color, sometimes almost with a little brownish or grayish tint. Amethyst Ruby is, to me, a truer violet. I have not come across the names “Light Amethyst” or “Dark Amethyst” among Carder’s formulas, which isn’t to say that I might not have overlooked them. I do not know whether that which some would call “Dark Amethyst” represents Carder’s early, high-manganese Amethyst glass.

Perhaps other readers will have some information on the names Light Amethyst and Dark Amethyst, and we hope that they will be based upon written records and not hear-say.

Thank you, and I hope this what somewhat helpful.

Greg M.