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Re: high vacuum refill

Gary Schnabl wrote:
> Someone wanted to know why high vacuum (very low absolute pressure)
> refilling was bad... If the absolute pressure of a liquid decreases,
> the boiling point temperature decreases. Gases (vapors, in this
> two-phase case) occupy greater volume than their liquid phases. When a
> cartridge is evacuated (near zero absolute pressure), the first few
> drops of entering refill ink will vaporize (boil), taking up space. It's
>  not air, but ink vapors. The ink is boiling! I suspect that this
> boiling will be more detremental with low-speed high-vacuum refilling....

I pull a vacuum 2-4 times before filling with ink. Then 2-4 times
more after the first fill (with about 5ml of ink in the syringe, to
fill in that extra evacuated air). Then the excess ink on the top of
the cartridge (about 0.5-2 ml) is removed by syringe and needle. For
color inks, which I refill with the WeInk Ultra Fill kit, I omit the
post fill vacuum pulls.

The "high vacuum" achieved with multiple pulls on a 60ml syringe is
not sufficient to reach the effect described by Gary. When you clamp
off the tubing between the cartridge and syringe, remove the
syringe, purge the syringe by pushing on the plunger, reattach the
syringe to the tubing, and declamp the tubing; there is sufficient
air in the set up to prevent a super high vacuum.

If you add isopropanol to the ink, and warm the cartridge in a hot
water bath, and pull a strong vacuum with the syringe, some of the
solvent mixture does boil (this applies to pulls after the first
fill). This helps purge out trace amounts of air. The space occupied
by solvent vapor vanishes upon return to atmospheric pressure and
room temperature. Then I remove the excess ink from the top of the cartridge.

Gary's concerns may be valid if one uses a fancy vacuum pump with
air tight valves instead of 60 ml syringes.

-- Ben Haskell

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