Let both doughs rest for about 1 1/2 hours or until doubled in size.
Turn each dough onto lightly floured surface and divide and shape as follows:
Divide each dough into 4 even sized pieces. Roll each piece with a rolling pin an oblong about 5 inches by 8 inches long. Stack light rye with a dark rye, light and then dark. Roll this stack up into a batard and seal the bottom. Repeat with the remaining loaves to make 2 loaves.
Place the loaves in parchment lined or greased loaf pans. Mist with spray oil and cover with plastic wrap. Let rise for 60-90 minutes or until nearly doubled in size.
Preheat oven to 350 degrees. Whisk egg with 1 teaspoon water. Brush evenly over top of loaves. Bake for 45 minutes. If using a thermometer temperature should reach 190 degrees F and loaves should make a hollow sound when tapped.
Remove immediately from pans and let cool on a rack for at least 1-2 hours before slicing.