I have a recently acquired mercury manometer which, I have read, is commonly referred to as a "stick" manometer. It is a Pyrex model 6952 and has an glass inner tube (gets filled with Hg) that fits into an outer (partially filled) graduated (mm) glass tube. I followed the filling instructions to a tee: attatch rubber tube to inner tube, pour in Hg, tap to get Hg into inner tube, heat inner tube gently to remove air (with filling tube still attatched) etc. I don't have any instructions for the use of this manometer, but according to Zubrick the level of the outer tube is subtracted from the level of the inner tube. The problem I have is that when I take a vacuum reading with it the level in the inner tube goes below the level in the outer tube (just slightly- maybe 1mm). Zubrick says there must be air in the inner tube. So I repeat the filling procedure but pretty much get the same reading. Am I not heating the inner glass tube enough to remove any trapped air? I tried to heat it just enough so as not to start to melt the silicone rubber filling tube attatched to the end. Any ideas anyone has are appreciated. -Zero