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Jeff Liebermann Jeff Liebermann is offline
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Default weather instrument barograph ink resource and pen modification?

On Mon, 27 Jan 2020 15:40:47 -0800, (Dave
Platt) wrote:

In article ,
Jeff Liebermann wrote:

To make a slow dry ink, I would guess that the ink should be high
viscosity so that it doesn't drip or run. It should also be high
surface tension to slow evaporation. The high surface tension is easy
enough by adding a few drops of a wetting agent such as Kodak Photo
Flo 200:
https://www.bhphotovideo.com/c/product/28195-REG/Kodak_1464510_Photo_Flo_200_Solution.html


As I recall (and as that page states), Photo Flo is a surfactant,
which _reduces_ the surface tension of the water. This makes it
easier for the water to "wet" the surfaces to which it's applied. The
water spreads out more quickly and (as the page says) "promote[s]
faster, more uniform drying."

Probably not what you want, if you want ink to stay liquid.


Oops. Surfactants and wetting agents are used to reduce evaporation
is correct. However, mangled everything else. To reduce evaporation,
surface tension should be lowered, not raised. Surfactants and
wetting agents lower surface tension. Adding Photo Flo to the ink
will still reduce evaporation, but not in the manner that I originally
described.

Study of Surface Tension, Natural Evaporation, and Subcooled
Boiling Evaporation of Aqueous Surfactant Solutions
https://commons.erau.edu/cgi/viewcontent.cgi?article=1304&context=edt

Of course, nothing is simple:

Surface Tension and Evaporation
https://chemistry.stackexchange.com/questions/61813/surface-tension-and-evaporation

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