Several months ago, we were sent a box of Covid tests by the government, because we live more than 20 km from the nearest testing station. They expired in December, and we had never so much as opened the box, so I let the school children experiment with them. They tested all sorts of things… lemon juice, kombucha, whey, broth, mud, cow poo, the cow’s nostrils (the milk cows were right outside our windows that day). Much to their disgust, nothing tested positive! I enjoyed watching them write down their predictions and the results they got.