Answer to Question #2246 Submitted to "Ask the Experts"

Category: Consumer Products — Watches, Clocks, and other Glow-in-the-Dark

The following question was answered by an expert in the appropriate field:

How are gas mantles manufactured for Petromax without using thorium nitrate?

First of all, there is nothing unique about the mantles used by Petromax. The same type of mantle is also used in Coleman gas lantern mantles. The mantle fabric is initially saturated with a mix of yttrium hydroxide and cerium hydroxide. The ratio is approximately 3 parts cerium to 100 parts yttrium. When burned, these compounds are converted to the metal oxides.

As I understand it, yttrium-containing mantles have a lower light output than those that employed thorium but they aren't as fragile and they have a longer life.

For details, check out U.S. Patent 4,533,317, patented August 6, 1985, by the Coleman Company (filed August 29, 1983).

Paul Frame, CHP, PhD

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