There's a Welshman in the waterworks

I am glad to welcome back once more Dr Rudolf Reinhardt, the expert on bathroom science, who will answer all your questions about the strange scientific phenomena which occur only in bathrooms and nowhere else. All yours, Doctor!

Can you tell me why the bottom of our feet sometimes stick to the bath when, for instance, we are having a shower. I have occasionally nearly fallen headlong through not realising that I couldn't easily lift my foot from the enamel!

Dr Rudolf Reinhardt writes: Oddly enough, this is a relic of our primitive days as hunter/gatherer/ fisher-men. Our forebears used to spend hours motionless on the rocks with spear aloft, waiting to skewer a passing fish, and their balance was considerably helped by the ability of the feet to exert a gentle suction effect on the stone surface. Some of us still retain this ability in the bath.

Speaking as a man who still enjoys the good old-fashioned wet shave, with brush and shaving block, I often wonder why we bother to put so much foam on our faces. It is only the foam which is in contact with the skin which has any effect on it, so we might as well forget the rest. It would make more sense just to draw a thin layer of foam across the face and then shave it off. But we don't! We insist on creating a huge bundle of foam, ending up looking like Father Christmas, which all has to be removed and which drags out the shaving process no end. Why do we do it?

Dr Rudolf Reinhardt writes: Oddly enough, this is a throw-back to the time when beards were the rule not the exception. As far as we can make out, primitive man used to shave once a year, that is, when the beard was getting too matted and unruly, and when he wanted to start all over again. So every time he shaved, he shaved the whole beard off. Our modern shaving technique is an echo of that - the modern faceful of foam is a replica of the whole beard and it gives us a feeling we are again removing the whole beard!

You know when you turn on a hot tap in a bath or basin and it runs cold for a while then starts running hot? Well, I can always tell when it is changing from cold to hot because the sound changes - there is definitely a different noise made by cold water from the noise made by hot. But why does running hot water sound different from cold ?

Dr Rudolf Reinhardt writes: Oddly enough, there is no difference in the actual sound of water - there is only a difference in the way we hear it. One of the primitive attributes of man was an ability to hear better in cold conditions, when danger was more acute, and a gradual shutting down of the hearing faculty in hotter, safer conditions. So it is the actual change of the temperature of the water, which warms the air in the room and therefore affects the way you hear things, not any change in the noise.

Why does bathroom soap so often get veined with black lines of dirt, ingrained in it like, well, like black lines of dirt ?

Dr Rudolf Reinhardt writes: Oddly enough, this goes back to the time when the only way we could clean ourselves was by rubbing ourselves with rock (as we still do with pumice stone), and soap ingrained with dirt is very reminiscent of a smooth piece of rock. We don't think of dirty soap as dirty soap but, rather comfortingly, as a large veined pebble - the atavistic memory of cleaning ourselves with rock prevents us from cleaning the dirt out of the soap.

I have been given a present by a relative who has just returned from Japan and which I am told is very good for you. It looks like a slightly rough flannel and is used to rub yourself after a bath or shower in order to get rid of all the dead skin which flakes off in daily life. Do you recommend this from a scientific point of view ?

Dr Rudolf Reinhardt writes: In theory, yes. Oddly enough, however, I should point out that after generations of rubbing away at themselves, the Japanese are now on average smaller than most people.

Why have so many of the recent crop of Irish comedians got Welsh names? Sean HUGHES, for instance. And DYLAN Moran. And ARDAL O'Hanlon sounds a bit like ARWEL Thomas ....

Dr Rudolf Reinhardt writes: What on earth has this got to do with bathroom science ?

Nothing. I'm just fed up with all this pseudo-palaeontology bathroom stuff, so I'm trying to change the subject.

Dr Rudolf Reinhardt writes: Well, you're on your own, mate !

Dr Rudolf Reinhardt will be back again some day, if he is not too offended by that last questioner.