Talking of coal fires, we used to have an open fire which used Glowco (not sure of the spelling) My mum used to use crumpled newspaper to light the kindling wood to light the coke. Usually this was OK but about that time the newspapers started coloured pages, which, when removed from the bulk of the paper were 4 pages which were covered in ink and completely different from all the other sheets. The issue was, that for some reason, the coloured sheets just didn't burn the same way as the plain ones and caused issues starting the fire. Try is I might to explain to my mum that she shouldn't use the coloured sheets, it fell on deaf ears.