On Mar 27, 8:02 pm, "Joe" wrote:
On Mar 27, 6:08 pm, "Remi" wrote:

My wood burning fireplace has a lot of missing mortar between the bricks
right behind where the logs go. I went to Home Depot and they sell fireplace
mortar in a tube (the kind you need to use with a caulking gun). The area
that needs the mortar has a lot of soot around it. Would I need to clean the
soot off before applying this mortar stuff? If so, how does one clean years
of soot? Thanks.

I might be all wrong about this, but given that problem here's a way I
would try: first, wire brush , scrape, whatever to get as much loose
crud off as possible. Then open the damper, bring in the propane tank
and weed burning torch, and slowly, gently, bring the affected areas
up to a temperature that would blue steel nicely. We're assuming that
the firebrick has no hidden crevices exiting to flammable structure,
but it would pay to check. This should work, because carbon deposits
will slowly oxidize somewhere around 800 F IIRC. Following this, the
firebrick mortar should adhere perfectly to the clean area.
For more ideas on cements, mortars, techniques, and such, try
contacting folks who work in ceramics and build kilns for their wares.
HTH

Joe

Just scrape it clean and brush off the dust and point the joints with
2 parts sand and 1 part portland cement. Not too much water. Just
enough to make the cement the consistancy of stiff putty. Do not put
a fire in there with severely cracked mortar joints. You don't know
where the smoke will go.