Not sure what to make of those comments..I've owned several modestly priced liquid filled compasses, plus one or two expensive ones and none had bubbles when bought..
I've read somewhere that a change in altitude and induce a bubble to form, but after flying with a couple in my kit over the years, I can't say I've seen it happen..
When (if) a compass does develop of bubble, I generally bin it and then replace... [/quote]
Actually Pete, liquid filled gauges of any sort will have a bubble to offset the expansion and contraction of the case allowing the air to also do the same as liquids do not compress. This saves the crystal and frame from warping and leaking in oil dampened gauges.
