And indeed life was like the churning and stinking of the butter-making process. "Brains turned crystals full of clean deal churns"; this is the poet saying that living and thinking was a process like making butter; you have to have something of substance to begin with, then you have to make sure it is "clean" and finally, it is complete.
Poetic form "is both the ship and the anchor," Heaney stated in his Nobel lecture. Poetry holds the power to "persuade that vulnerable part of our consciousness of its rightness in spite of the evidence of wrongness all around it." And when a poem like Churning Day is presented, it helps the reader in 2007 - while shopping at Safeway for a pound of butter in neat quarters - remember that butter was once made at home in an elaborate and smelly process, and that mothers got blistered hands and aching arms so the family could enjoy their meal.
While war was very much in evidence in young Heaney's life, it is also very much a part of the news in present day life. And though it is a very different war fought for very different reasons than WWII was fought, the taste of butter has remained the same.