I have been working on this print trying to experiment with the contrast controls using my new enlarger with a variable contrast light source which consists of two neon tubes in a grid.  One neon tube emits a green light which lowers contrast.  A print using light only from this tube would be similar to a 0 filter.  The second neon tube is blue and controls higher contrast if this light is used alone the contrast would be similar to using a 5 filter.  If both are used at the same setting contrast is similar to a 2 filter.  This particular image was taken with infrared film and the paper I printed on was Ilford VC warmtone semi-gloss.  Semi Gloss has a pure white base color.   This combination produces a contrasty image and I was trying to soften it.  The clouds though appeared pure white and deep shadows and certain colors like blue and red print out as pure black.   I decided on a particular start point which was E F which I assumned would be equivalent to a 2+ a higher "hard" contrast setting then the "soft" setting.  I then tried to determine the time of exposure by doing a test print in 2.5 second or exposure unit intervals hopefully going from hardly any exposure on one end and too much on the other. This was much easier with this "higher tech" timer that measures time down to 1/10th of a second and can hold the exposure rather then having to be reset and only having one second intervals like the old fashioned Gra-Lab timer which I have always used.  Also this timer measures exposure units rather than seconds so changes in light intensity change the duration of each exposure unit.  My goal was to produce a print with a good range of middle values, various grays and a pure black and less than pure white.I proceeded to reduce the "hard" settings leaving the "soft" settings alone.    The problem is the sky which was coming out pure white.  This may have been an issue because exposure was made for the light reflecting off the area below the sky retaining shadow details but over exposing the sky and bright surfaces.  The infra red film doesn't absorb the blue light so the sky comes out black, but the clouds are over exposed.  Pure white in a print should be reserved for a light source or glare of a light source off a reflected surface. Film though can only cover a limited range of values.  Since there were areas in the picture where no light was reflected I was okay with a pure black but I wanted the clouds to be the lightest value of gray rather than pure white.   Once I get all the middle values the way I want them I'll leave the darkest areas of the print alone and then "flash" the paper to shift the clouds from pure white to the slightest exposure possible or the lightest shade of gray. Flashing paper or pre exposing paper to eliminate Zone 10 or paper base is one way of manipulating the tonal range in the finished print by eliminating it.  This should be easy to do with the new t timer that can reduce exposures to a fraction of a second.  When you flash paper you want the minimum exposure possible to eliminate paper base where no exposure of the paper is made.