One edge of the paper is slipped under an enlarging easel blade and five clean metal
washers are distributed along the exposed area. With an enlarger or very small bulb set to a
distance, lens opening, etc. that is recorded and repeatable, the whole strip is given exposure
X. Then the first section is covered with an opaque sheet and the remainder given exposure X.
The sheet is moved to cover the second section and exposure 2X is given. Subsequently as a
section is covered, the next gets 4X, then 8X. As a result, the sections get total cumulative
exposures of X, 2X, 4X, 8X, 16X; a five stop range. The case at hand used a 6x6 enlarger
with lens 24 inches above the easel and the lens on f/32. This was Arista.EDU RC Grade #2
and the X value was 0.2 seconds; the obvious sections had a total of 1.6 and 3.2 seconds
exposure; the center section had 0.8 seconds (it may or may not show, depending on your monitor).
As such, we chose to use 0.7 seconds in pre-flashing the paper to be used as film.