[HN Gopher] What Is the Transparent Material at the End of a Gel...
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       What Is the Transparent Material at the End of a Gel Pen Refill?
        
       Author : thomas
       Score  : 16 points
       Date   : 2021-05-02 13:50 UTC (9 hours ago)
        
 (HTM) web link (unsharpen.com)
 (TXT) w3m dump (unsharpen.com)
        
       | EricE wrote:
       | Nothing beats a Fisher Space Pen!
        
       | bernulli wrote:
       | "Gel ink is viscous, but it's not thick enough to prevent it from
       | flowing. This means it can evaporate over time"
       | 
       | These are three different, unrelated phenomena. In a Newtonian
       | fluid, no matter how large the viscosity, the fluid will flow
       | when a shear stress is applied (think honey).
       | 
       | A gel is instead typically a non-Newtonian fluid, i.e. a certain
       | threshold stress has to be reached before motion sets in (think
       | toothpaste).
       | 
       | I don't really see why the author then relates evaporation to
       | viscosity. Shielding the fluid of interest from mixing with the
       | surroundings will prevent evaporation (close the bottle of water
       | and it will remain full, leave it open and then it will evaporate
       | eventually).
        
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       (page generated 2021-05-02 23:02 UTC)