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If a window was coated with a fluid film it could remain clean
To achieve this the window has a fluid outlet extending along
top edge. Fluid runs out of the outlet and down the window. At
the bottom of the window a gutter collects the fluid. A pump
pumps the fluid back
to the top via a filter.
If the fluid remains laminar as it flows down the window then
fluid would be a transparent film. Occasionally losing the
flow would be OK (e.g. due to wind), but this could be
minimised (e.g. using fluid of higher viscosity).
To ensure laminar flow several parameters would need to be
carefully chosen such as: viscosity, speed, outlet cross section.
Glass treatment apparatus and methods of treating glass
Youll need something like this to create laminar flow [kdf, Aug 11 2020]
Self cleaning windows
Titanium dioxide coatings [kdf, Aug 11 2020]
||Honey would be viscous enough! But you might end up with too many bees stuck to your window.
||Also, if "indefinitely" means "for an ... unspecified period of time" or "not certain in amount or length" then I would say that my windows already remain clean indefinitely, just not very long.
||See linked patent for how you might create
laminar flow over a glass surface. Glass coated
with titanium dioxide is somewhat self cleaning
when exposed to sunlight and normal humidity,
your idea might enhance the effect.
||But... how do you keep the INSIDE clean?
||^ :waiting for [8th] to offer mildly toxic high-pressure fire
hose-delivered chemical-laced solution:
||If it's any comfort to him, the process of extracting the Ti02 from
mineral sands involves some highly toxic fumes.
||As usual, I would go one step further:
Use a transparent thermoplastic, extruding quite thick from
the top slot/nozzle, which is then collected at the bottom,
melted, filtered, pumped to the top again, cooled, rinse &
No "fixed" pane at all.
||I never did get around to posting it, but years ago I had an idea for
something like this on car windshields, flowing UP and back.
Thought it might help reduce damage from rocks and splatter from
insects, and MAYBE reduce wind resistance a tad. [+]
||Open to pranks of dyes and soap solutions, depending on the fluid.
Such a small cycle open to the environment, I just can't see it staying pristine.
||The device could have a sensor to detect significant
impurities (bird poop, dyes, soap) and could divert the
impure fluid to a waste reservoir.
||The recirculated fluid will eventually become visibly impure
(even with the diverter). The sensor could alert the user
when it is time to replace the fluid. The fluid would be
relatively cheap to replace.
||I would estimate it costs about $10 per window per year to
keep windows clean (i'm thinking multistory office
buildings). As long as the running costs of the system is less
than that, it should be a viable product.
||//Honey would be viscous enough!//
||My honey has turned vicious. Perhaps I should start putting
the toilet seat down. Me cleaning the windows might help
||^At least your putting the toilet seat up.
||Out of all of the things in the world, glass is about
the easiest to keep clean. We hold it to high
standards because it's totally clear and we have
outstanding visual perception. Still, glass has
excellent cleanability properties, it's often totally flat,
non-porous, chemically inert & temperature stable.
It's also super hard and difficult to scratch while
being made of one of the cheapest possible
materials. Amazing really.
||To improve upon that, you propose a liquid filtration
system open to the elements. My aquarium is a
reasonable analog of that. If someone offered to
keep that as clean as my windows for $10/year I'd
bite their hand off. The hard part is choosing the
liquid. It can't evaporate, can't be compatible with
life, can't be hygroscopic, must be as clear as glass,
cheap, non-toxic, the correct viscosity etc.