Color curve chart

There's a chart listing ambient temperature, surface temperature and
color that composite builders take as gospel. I'm trying to get more
information about it

http://hallert.net/cozy/images/ColorCurveChart.gif

It originally comes from the Long EZ plans, Chapter 25, page 1 in the
plans and there's a handwritten note on the chart that says "Soaring
Sept 1975."

I have a call in to SSA, and they haven't been able to find a copy of
that issue. Does anyone have a copy?

In the testing that I'm doing, these temperatures seem high. White
surfaces don't seem to be more than about 10 degrees F higher than
ambient, the chart shows a white surface on a 30 degree day at 85
degrees. Yesterday it was hot in So Ca, 90 degrees ambient - but
black surfaces were coming out at 185, not 210.

If anyone knows what methods were used to gether these numbers, I'd be
thankful.