I have had this and Silva say if the bubble is small (below 1/4" iirc) it's ok. It's due to atmospheric or temperature changes. Having said that, I always carry a spare compass after once leaving mine sitting on a rock on Skye!
In reply to Flinticus:
I've had similar issues with silva compasses, again, I had two with me and both had the same problem.
I was also told by silva that it was due to atmospheric pressure and temperature. This would seem to make sense as the bubbles only appear on very cold clear days.
In reply to Flinticus:
I noticed last weekend for the first time that my Suunto compass has a (very) small bubble - it's around 15 yrs old.
My original compass (inherited off my Dad) had a big bubble and TBH so long as you jiggled it so the needle wasn't resting on the bubble there was no problem with reliability/accuracy
Someone told me the bubble was quite normal, that it allowed for expansion or contraction as temperature changed and avoids the compass bursting - gas being compressible but not liquid.
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