My father was reminiscing today of his time as an apprentice in Crewe Works during and immediately after the Second World War. He spent some time working on the “element belt” where super-heater tubes were repaired, but he also mentioned the uses to which badly worn locomotive boiler tubes would be put. If a tube was impossible to repair to a standard so that it could be used in a steam-loco’s boiler again, then it would be used for various “fabrication” jobs. I’d heard of their use in welding up steps for signal-boxes and the like, and I may have heard of their use in making up tubular signal posts. What I’d never heard of was that they used to paint the inside of the signal posts.
Painting the inside of a signal post is not, now I think about it, a stupid idea. The post needs to be protected against rust and that applies just as much to the internal parts as the outside. Once it had been fabricated into the desired shape – several feet long and only a few inches in diameter – then the inside would be painted with bitumen. Naturally, there would be no niceties lost in doing this. The tubes would be racked up on a slope and bitumen poured down the inside. Once it reached the end of the tube, then the tube would be slowly rotated until the entire inside had been coated with the thick, black substance. Elegant, it was not, but then it wasn’t visible, either. Which accounts for why I’d never thought of the possibility before of painting the inside of tubular signal posts.