|"Actually the mirror will reflect more light than paint most mirrors are over 90% efficient and some near 100%, and I've never had a plant catch fire from aluminum foil."[/QUOTE]|
Actually you are wrong mirros eat light just like glass only worse,
with a mirror the light is sent through the LEADED glass and then hits a reflective LEADED backer which it then bounces off of and passes once more through the LEADED glass, then it may proceed to you plants leaves.
If you really want to know what the efficiency of a given surface is you need a spectroradiograph, gl.
The hotspots I was refering to were not in reference to a fire, they were in reference to burning your plant with too much light and excess heat, the uneven suface of tinfoil does not reflect light uniformly and is thus extremely inefficient.It also reflects heat back into an enclosure this is why mylar is prefered it has reduced capacity to relfect heat due to its physical qualities.
This is really the only thing I recommend Aluminum foil for, http://zapatopi.net/afdb.html.
Hehe, its my favorite site. [img]http://www.**********.com/iB_html/non-cgi/emoticons/wink.gif[/img]
Glass does not "eat" (absorb) very much light, in fact most glass has a very high transmittance (photons pass through unaltered, near 100% transmission). This is why you can clearly see though a pane of glass. The photons of light are unaltered, they do not change direction, and very few are absorbed. The reflective surface on the back of a mirror is very efficient, if it absorbed a high % of the photons it would not work to view your image in it. By having a high reflectance of the light it does not impose its own physical coloration on the wavelengths of light reflecting off of it (which gives materials of high reflective value a silvery or metallic look). Once again this is why an image in a mirror appears clear and undistorted. White paint on wood is a good reflector but not as good as a mirror. A simple test with a flashlight will prove this, at night shine a light onto the paint at an angle vs. a mirror or aluminum foil at an angle, there will be much more visible light reflected back onto your plants from a mirror or tin foil (or mylar I not arguing with that) than the paint. Your forgetting that its not just a white paint but also the texture of wood underneath it, and both absorb many more photons than a silvery reflective surface.
As for hot spots, the tinfoil has tiny creases but no major indentations (there are no parabolas to condense light and therefore burn the plants), and any heat forming in the layer of tinfoil itself is fine in my setup as temps are not a problem.
01-18-2003, 04:27 PM
Im sorry but i still disagree with you, I would like to see some one with a quality light meter, or quantum meter for that matter, run a comparison I can gaurantee you your not going to see 100%.
First of all your speaking in terms reletive to the human eye not a plant. The human eye can only interpret a very narrow portion of the spectrum. Plants have been designed to absorb light over centuries. The fact of the matter is that the Human eye absorbs more green that any other portion of the spectrum and that is the main protion relfected by plants. So regardless of the fact that you think you are recieving more light, you are not. This is the same reason why Lumens dont mean anything to plants.
"there will be much more visible light reflected back onto your plants from a mirror or tin foil "
Keyword visible, thank you for re-enforcing what i just stated.; )
PAR is what needs to be messured in order to get an accurate measure of usable light for plant growth, not a flashlight and a mirror.
Photosynthetically Active Radiation (PAR): *A measure of visible light intensity (400-700 nm) obtained by using a quantum meter. * PAR is simply a count of photons falling upon a surface in a given time and is reported as “micro Mols per square meter per second” (µMols·m2·sec). *Quantum meters report all wavelengths between 400 and 700 nanometers. * However, they report only light intensity and do not account for spectral quality. * Generally, maximum solar PAR values are 2,000 – 2,100 µMols·m2·sec. * PAR is something of an outlaw in the scientific community; it is not recognized as a standard unit, however most major works in the field (notably Kirk (1983), among others) state compensation and saturation points in PAR units. *(Since PAR is a relative new-comer to science, it has not been recognized by CIE (Commission Internationale de L’Eclairage) or the International System of Units (SI) – both had already adopted standards for measuring light intensity. * Lack of recognition by either of these committees should not undermine the importance of PAR measurements. * Incidentally, divide µMols·m2·sec (of sunlight) by 4.6 to convert to watts per square meter per second (which is a SI-recognized unit.) *A quantum meter is better suited for reporting light intensity than lux meters. *Lux meters are photometric in their response, that is, they “see” light as the human eye does and have a maximum sensitivity to green wavelengths. The human eye is not especially sensitive to those wavelengths known to promote photosynthesis (violet, blue and red). * Generally, noontime lux measurements made on cloudless days in the tropics range from 100,000 – 120,000 lux.
I used to have several graphs tracking chlorophyll production at differing wavelengths, but i cant findem anymore.
Here are some links if your interested.
If you ever wanted to do some of your own testing heres some equipment to learn about.
Id also Like to know when lead stoped absorbing radiation of any kind.
As for the tinfoil It was just a general warning, in a glass enlosure its not much to worry about. As glass is such a poor insulator.