Black shadecloth definitely blocks more light than does white. There may be
some "quality" reduction on a 1-1 basis, but it would take at least 2 [and
I'm afraid maybe more] similarly-rated layers of white to provide the shade
of 73% black [what we started with, for phals, and had to add more shade to,
here in So. Fla.]

Second-hand: Aluminet has a number of customers buying its red and gray
products, or so they told me when they were here trying to sell me ... Not
so much orchid growers, mostly growers of flowering terrestrials. According
to Aluminet, these big growers move blocks of plants under different colors
of shade to time their flowering. FWIW. Kenni

"blass" wrote in message
...

I found a site (http://tinyurl.com/8znl8) selling shade nets. And this
is what they have to say or warn (darn, why now?) before buying their
shade nets:


*-Caution-

Green and black shade nets behave like filters. Essential radiation for
photosynthesis is reduced.
Thus, the growth is reduced. A green and black shade net decreases the
light's quantity and spectrum quality.

White shade nets :
They decrease only light's quantity, without altering luminous'
spectrum quality. As a consequence, the plant's growth is faster with a
white shade net.*


--
blass