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Chads93GT wrote:Its an oil. throw it in the freezer so it expands and the bubble will disappear.
Lol I think I have it backwards.........heat will make it disappear. did you have the compass out in the cold? that generally causes air bubbles.
fr73ed wrote:I refilled with some light oil, jet A or somethin, don't remember , and attempted to seal it back up with several types of epoxy.
Never could git it to stay closed.
The oil prevented a good adhesion.
I can describe the basic ideas.
You (and the original makers), want something clear and non-yellowing,
moderately viscous, and harmless to metal and paint.
Mineral oil is pretty good in that regard.
100% Isopropanol would not be terrible, but it is not very viscous and
leaks and evaporates.
Glycerin is viscous and will not corrode metal (might even dissolve small
amounts of water leaking into the case, protecting metal from corrosion).
However it is a strong solvent and kills most paint in the not-too-long run.
It does the same thing brake fluid does to auto paint, but slower.
Fluorocarbon oils are entirely safe for paints, but it is overkill, and I
am sure that is not what was used in 1943.
Silicone oils can be harmless too.
At this time, you want something mutually soluble with the old oil.
so you need to get some of the old oil out of the compass to try it.
Put a drop into each clear glass of:
- water,
- drug-store mineral oil, (or maybe vegetable oil is quicker for you)
- 91%-grade rubbing alcohol (91% isopropanol, 9% water)
- drug-store glycerin
and let them sit still a while,
and watch to see which one bends to near-invisibility first, instead of
staying in a sharply-defined glob.
Only wiggle or shake if it takes longer than an hour to dissolve.
If shaking makes the solution cluttered or milky, that is bad, very insoluble.
My guess the mineral oil will dissolve first and smoothest.
I might keep all the old oil that can be poured out in some tiny bottle,
and fill the compass with the new mineral oil.
The most conservative way to clean out old oil is to refill with you
chosen new oil and shake or soak, then pour out and refill again.
If you wish to do a quicker or more thorough clean-out of old oil or new,
then 100% Isopropanol is your safe universal solvent that can evaporate to
dryness.
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