I had worked with charcoal before in primary school and knew what the material was like. I'd bought some for myself in my early teenage years to experiment with it but due to it always leaving prints everywhere I gave up on it pretty soon. About 12 years later we were told to go outside of school and draw something with charcoal on location on a paper 3,5 times the size of an A4 paper sheet, which was very inconvenient as there was nowhere you could lay your paper on. I can't remember drawing these cubic houses at all but they are located about 500 meters away from school and for a quick sketch they came out quite nice