By: Blonde Two
I often (well sometimes) wonder whether we should give up spending so much money on waterproofing ourselves against the rain, and just go out in our skin. I also wonder sometimes whether or not I am a bit odd. However, if you want to find out more about hydrostatic head, outdoor gear and tent waterproofing, read on.
But think about it. Skin must surely be waterproof; if only we could find a way to give it better thermal properties, we would be onto a winner. I am obviously sparing no thought here for those who would have to look at us wandering the hills in the buff (not the tubular scarf thingy we all love so much!) Skin’s waterprooficity (Blonde word) is apparently down to lipids with two tails and one head (Blonde science); if you want to find out more, read this New Scientist report.
What is Hydrostatic Head?
Theo outdoor retail world is very keen on its waterprooficity ratings. For example if you were buying a tent, you might consider its hydrostatic head. This is sadly nothing to do with many-headed monsters. It is, however, to do with a column of water. Imagine a test tube with no bottom; to measure the hydrostatic head of a tent, you would place this otherwise useless test tube against the canvas and fill it with water (not apple juice) You would then watch for when the water started to seep through the canvas, and measure in millimetres, how tall the column of water was when it started to do so. Hey Presto! Hydrostatic head!
Waterproofing IP Codes
Another waterproofing measurement is written in code. I don’t think this is because it is a secret; but I think someone really important must have invented it. IP Codes were created to avoid the vagueness of the term ‘waterproof’. For example, one could argue that cling film is waterproof; but you wouldn’t want to sleep under it in the Brecons would you? IP (unless you are a computer) stands for “International Protection Marking” or sometimes “Ingress Protection Marking”. In the outdoor world, you might see this in a dry bag. IP66 for example would mean “dust tight” (the first 6) and “protected against powerful jets of water” (the second 6). If you wanted your dry bag to be fully immersible, you would probably go for IP67 or IP68.
And finally, most of us know that stockings come in different deniers (the thickness/weight of the thread); but did you know that other fabrics do too? Take my Exped Dry Bag for instance, it is quite old now and has taken some knocks, but it has served me well. Its fabric is 70D, enough to keep things dry in my rucksack, but not enough to take kayaking. This OverBoard Dry Bag is much thicker; at 600D, it should keep my kit dry even if I dropped it in a bog and stamped on it.
I am not going to do that though! It is far too pretty!