Resin lamps
I had a long phone call with my oppo, he of the Halifax rebuild, and he says he never heard of resin lamps. He is very knowledgeable, and told me that when he was in Italy, he designed an I.R lamp which would transmit a signal via aldis lamp, that was not visible to the human eye, but could be read by a two valve receiver some distance away . A thin sheet of ebonite ? was placed in front of the Aldis lamp, which then only emitted infra red, also known as black light, and was invisible. It was very successful, but when the C.O found out he was told to forget it, and get on with the work he was paid for.
Sorry CLIFFNEMO