Radium silk

As the deleterious effects of radium on the human body became better known in the middle-1920s, the use of the word as an adjective gained a negative connotation and fell out of favor among advertisers and consumers alike.

[1] The term apparently originated in the fashion markets of Paris in association with particularly lustrous fabrics, with reference made to the newly discovered element radium, first identified in 1898.

A September 1906 syndicated plate, appearing in dozens of newspapers around the country, enthusiastically described the "exquisitely toned material which has had such vogue in Paris for the last few months.

Heavier and finer weaves than the latter, it has all its graceful clinginess, with greater durability, while the softness and simple patterns of the former are enhanced by a high sheen, caused by being woven of organzine so fine that the single thread is barely visible.

A pink will have the soft blush of the heart of a shell; the tint of the sky shining through a fleeting cloud on a sunny day is seen in the blues, while the lavenders, greens, yellows, and even the darker colors all have the soft undertones that gives them a beautiful iridescent effect.Although many consumer products of this era were made containing radium, which was initially believed to have highly salutary properties, bright and shiny radium silk did not.

Radium silk was particularly popular for use in women's loungewear and undergarments. It was also used in gowns for weddings and evening wear and for fancy garment linings.
The product name "radium silk" was already in common enough use for a California department store to lead with it in this July 1903 sale advertisement.