I'm reading the book: automating hydroponics, from Cerreto Rossouw.

He wrote, p46, "you shouldn't use aluminium foil because it's quite poor at reflecting light (...) A practical alternative (...) matte white paint, wich is 75-80 percent reflective"

well, I wonder why aluminium foil is poor at reflecting the light in comparaison of matte white paint. Is it the same for an aluminium mirror ?

  • $\begingroup$ the paint scatters the light so it gets spread nicely around the room. $\endgroup$ – PhysicsDave Mar 13 '19 at 18:38
  • $\begingroup$ I think that the author means that matte white paint may be better as a diffuse reflector of light, which is the property of interest for this hydroponics application. A flat aluminum plate or foil is of course a better specular reflector of light than matte white paint surface is. $\endgroup$ – user93237 Mar 13 '19 at 21:36
  • $\begingroup$ your comments make sense $\endgroup$ – The Unholy Metal Machine Mar 15 '19 at 16:12

The statement is untrue - aluminium reflects around 90% of the incident light.

The difference between aluminium and white paper is that aluminium is glossy and acts as a mirror. Therewith is "shows" the darker objects in the surrounding which may appear as being darker.

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