What Thaws Out First?

[Springfield Acer]

There has been threads about partially frozen sap in buckets and that if it does not get too cold, only the water freezes leaving concentrated sap.
When completely frozen sap thaws partially, does it happen in the reverse sequence?
I had an inch or so completely frozen in my buckets. Now that it is thawing, I'm reluctant to toss the ice.
Any thoughts?

[Gary R]

This is just a guess, I have drained my flue pan twice this season and the buckets have frozen solid. As they start to unthaw (over a couple of days), the most sugar comes out first. If you let it thaw more a little less sugar comes out. The color of the ice block eventually is crystal clear. Another thing to note, if for say, one gallon thaws from a solid 5 gallon block, the sugar settles to the bottom of what melted. If I sampled the top liquid without disturbing it might read 4%. Give it a stir and it might read 10%. When is it not worth thawing the ice any more? I have a couple of blocks laying in the yard if you want to play:)