I recently began removing and re-chinking a log home in Door County, WI. I used a recipe of 6 parts silica sand and 4 parts type M mortar. The logs were kept dry and much of the work was done in the sun. The next day we had several hair line vertical cracks. What causes the cracks? How do I need to change the recipe to prevent the cracks? Do I need to redo the chinking?