I have cleaned with all prod and seales the fire place and still have this problem
The bricks are at least 25 years old
We dot not use the fireplace
Help
Thank you

Ed

It can be sweating,condesation and most likely a ventalation problem. I have the same thing in a cottage I maintain and every spring it comes back. There may be a small leak at the chimey and roof area that will cause this powder to form. I do have some picts somewhere of the white powder and if I can find them I will post them.