Yesterday I had a solo mooch around some of the more remote bits of Upper Flood Swallet with the aim of testing for the presence and strength of draughts. Long story short, I tried using kiddies bubbles and it was pretty effective, if crude. If you just want to roughly confirm the rough direction and strength of a draught, then its a winner. 

Not as good as Maplins canned Disco Smoke 

Doesn't Disco smoke dissipate really quickly though? Another advantage with the bubbles is that they're tiny and therefore barely noticeable to carry any distance underground.

If the air is faint, might not blowing the bubbles obscure the direction of flow?

Not really. If you blow bubbles in still air, their air resistance soon cancels out the initial force of you blowing them in the first places for they remain relatively static. If they're moving after the first few seconds, then it's almost certainly due to an air current being present.

If you could put a bubble film right across a passageway then a draught and its direction would be obvious

Gerbil007 said:

Not really. If you blow bubbles in still air, their air resistance soon cancels out the initial force of you blowing them in the first places for they remain relatively static. If they're moving after the first few seconds, then it's almost certainly due to an air current being present.

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Hm. Might try it. I like smoke since it's so responsive, but I don't like to befoul the air with incense, which is what I most commonly use to hunt elusive air.

I thought the bubbles idea was good. If I can find some material might try it in a couple of days in our dig.

OMG. Foam pouring out of the dig. Remember the ruddy gap filling stuff.  :

Caving - The Bubble Theory.



Well we gave it a try and if anything it made me realise how hard it is to take photos of bubbles in a cave. This is near the end of our dig some 40 metres down. We have a moderate outward draught here with CO2 still around %2. Whether that effects bubbles I have not a clue. The bubbles aimlessly drifted into the dig then aimlessly drifted back out again. Many stuck to rocks in the high humidity. To my mind this confirmed not a sausage other than preparing Mr O'Doc for further sessions of grand parenthood. It may well be back to the smoke though we don't need it at the moment as the draught is ruddy freezing.

A selfie between bubbles this week. I thought it looked a bit spooky. Maybe the CO2.