A possible reason for air bubbles

[ThrillaMozilla]

I suspect that the method of storage of ink may affect the presence of bubbles in supply lines. Air is more soluble in cold liquid than at room temperature. If you refrigerate your ink, it will gradually dissolve more air, which will very likely come out very slowly in the form of bubbles after the ink warms up. Gassing and degassing can be very slow, so your ink can remain supersaturated with air for a considerable time -- possibly hours to months.

If it were mine, I would allow the ink to come to room temperature (or maybe slightly higher) before refilling, and I would shake it vigorously in the bottle to promote equilibration. You might worry that this could make the problem worse, but that's really not thermodynamically possible unless you warm the ink to a still higher temperature.

Obviously, there are also other possible reasons for air bubbles, but if I had that problem, I would consider the possibility.

I've been gone for some time, and I don't know about the extent of the problem, or whether you all have solved it. But I'm guessing you haven't.

 

[turbguy]

...or you can degas the ink before refilling by heating it slightly below the boiling point and cooling it before refilling (not recommended without testing, first).

 

[ThrillaMozilla]

That's a possibility, but I think it usually takes quite a bit of heat to nucleate bubbles in reasonable time. As you say, you might have to get it just below the boiling point. I would worry about ink stability and losing other volatiles.

I have to say that I've never tried degasing liquid by warming it and shaking it, but bubbling nitrogen through a liquid is a standard lab method for removing other CO2, so I think warming and shaking should also work to reduce the dissolved air. The idea is that all those bubbles give a lot of surface area to exchange the gas.

I don't know if people actually have that problem, but I'm guessing that they do.

 

[James Mike]

That's a possibility, but I think it usually takes quite a bit of heat to nucleate bubbles in reasonable time. As you say, you might have to get it just below the boiling point. I would worry about ink stability and losing other volatiles.

I have to say that I've never tried degasing liquid by warming it and shaking it, but bubbling nitrogen through a liquid is a standard lab method for removing other CO2, so I think warming and shaking should also work to reduce the dissolved air. The idea is that all those bubbles give a lot of surface area to exchange the gas.

I don't know if people actually have that problem, but I'm guessing that they do.

I guess a vacuum could be used to lower the boiling point of the liquid to prevent heat degradation of the ink however it does not solve the problem of other volatiles leaving the ink.

 

[turbguy]

On deaeration:

https://watertreatmentbasics.com/how-does-deaerator-work/