Hi. I live in a 35 year old wood frame construction home, 600 feet above sea level on the West Coast of canada. I have been noticing, 'white' deposits, on the inside of my bare concrete block chimney, below the level of the existing concrete wall, as well as on the outside of the form wall next to the chimney, but only on the exposed outer wall towards the front. Recently , we had some heavy rain, and now there is a 'water trail', that has followed the fireplace bricks, to the floor, and is also white in color. I cleaned everything off with a wire brush, and then 'painted' the inside basement bottom chimney bricks, the rest of brick works in basement attached to chimney, as well as those on the fireplace chimney where the water 'track' was, with Thompsons Water Seal. Today, there was a fresh, brush away, track of 'new' white 'stuff' where I had painted the water seal on, inside, downstairs, chimney, and on the foundation support wall that attaches to the chimney on the inside. There are 3 'flues' in the chimney, one for downstairs wood stove, next to it, upstairs fireplace, (not in use), and the last one, which is above the problem area, has the top 'sealed', and does not function. Today I went outside and pried the metal cover off of the side of the chimney where that capped flu is, and there is 'deposit'..(ash, chimney 'junk'), in it,but down below the level of the "door' by about 3 feet, so I left it open to the air....but, what is this 'stuff', that forms so quickly, and is white in color, and usually forms, on the mortar lines between the 'concrete blocks' on the inside of the chimney, and how can I fix this problem?