Whenever I make a fresh cup of coffee I tap my teaspoon on the top of the mug to shake off the froth.  The resultant sound increases in frequency with each tap. Does it have something to do with the sudden increase in temperature of the china mug?

Julie Newport

Brisbane, Australia

when im in the shower i touched the cold tap and my finger stuck to it and the same with the hot

In the past it seemed that men enjoyed standing around the barbecue turning the steaks.

Later everyone came to learn that this was bad, because turning the steak before it was fully cooked on one side allowed the juices to "get out". Legend has it that the meat must be "sealed" on one side to stop the juices getting out.

What are the juices that "get out" and where do they get out to?

If cooking on one side "seals in" the juices then why wouldn't it be better to quickly turn the meat to seal both sides before cooking?

Is there some advantage in only turning the meat once?

I've just opened a (paper) packet of flour that is 16 months past its sell-by date. It looks and smells OK and there are no visible signs of insect or fungus attack. What hidden dangers could lurk within it, or is it safe to eat?

I was photographing landscapes in a field under high tension power lines (see photo) when I discovered my metal tripod was delicately vibrating. I could only feel the vibrations if I rested my fingers lightly on the metal and they were clearly related to the high tension wires (not the gentle breeze). When I moved the tripod away from the lines the vibrations stopped, but returned when I took it back beneath the wires again. What was going on? More importantly, if the lines did this to a metal tripod, what might they have been doing to my body?

Alistair Scott, Gland, Switzerland

 Is the squirty cream from a can a solid, liquid or gas?

My wife and I use soya milk instead of cow's milk. It is fine when added to tea, but when added to coffee it curdles horribly. Why?

I order a coffee in Planetbucks. It comes as a cup of black coffee and a little jug of cold milk. I decide to postpone drinking it for 5 minutes. Should I put the milk in immediately or just before I drink it in order to have it as hot as possible?