The weather has turned cloudy and cool which has put the experiment on hold.

A couple of recent nights showed the effect of the dew point.  The first night the temp was 35 and the box was 32 and covered with heavy dew.  The next tight the temp was 36 and the box was 20 but no ice.  The bottom of the box was covered with frozen dew.  The third night the temp was 34 and the box was 17 with the water frozen hard and the saline mix slushy.  The box was dry.

It is looking like a dT of 17 degrees is attainable under the right conditions which would allow ice formation at 47-49 degrees.  Hope to resume the experiment in January.

This morning the "box" was 20 F with the ice frozen hard.  The outside temp was 35 F. with calm winds.  This 15 degree temp difference should get me close to my goal.

Recent trials included building a Styrofoam chimney around the box but this actually raised the interior temps above the outside air temps.  Adding a small amount of salt water brine to the pvc cap and using a small enamel cup for the distilled water definitely improved the ice formation.  An identical cup placed inside the box did not freeze.  The improved conduction must have overcome the phase change energy requirements. (I must credit my brother for this idea.)

Next step is to add some insulation to the outside of the box and raise the pvc cap up in the box to improve circulation.  Then I just need to wait for the perfect night with clear skies, low humidity, calm winds and the right temperature profile.

A fun experiment with no practical use...at least for now.