From Newsgroup: uk.d-i-y

The mild steel collar between the wood-burning stove and stainless steel
flue split at the back (hidden from view of course) and some of it was
lost through rust. A chimney leak a few years ago had allowed rain to
trickle down to the stove, and I guess was enough to rust and weaken the collar.

Dealing with the split and lost metal was a bit of an issue. The collar
did not appear on the stove spare parts list, and a previous repair to
the stove outlet pipe had required the services of a HETAS engineer. It
wasn't cheap. There was no way I was going to change the collar, so
decided to repair it with fire cement, and got a 1kg tub from B&Q. I'd
checked the info at <https://www.diy.com/departments/bostik-cementone-buff-fire-cement-1kg-tub/147432_BQ.prd>,
and it stated: "This fire cement from Bostik is ideal for repairs to
fire backs, internal flue pipes, solid fuel heaters and boilers."

It was only when I read the label small print after purchase did I find
out that it was not suitable for repairing metal! I wonder how many
"internal flue pipes" are not made from metal. The technical info
available at the Bostik website states: "Bostik Fire Cement is suitable
for repairs to a wide range of applications where heat resistance is
required, including fire backs, chimney linings, solid fuel heaters,
broken bricks in grates & stoves, boilers and other surfaces which may
be exposed to extreme heat and are not made of metal or plastic."

What nonsense! Are there many surfaces which may be exposed to extreme
heat and are made of plastic?! It also adds "Do not use in metal joints
due to movement & vibration". Despite this, I decided to use it, but
reinforce it somehow which would help prevent bits cracking off with
expansion movement. I used a small amount of rockwool insulation from
the loft, and mixed it in with the cement. This was then smeared
liberally over the SS flue pipe beneath the crack. I opened the steel
collar crack some more and jammed in more of the cement/rockwool
material. Finally, I fitted a couple of 115 - 140mm SS jubilee clips
over the cracked collar and tightened them until the collar was back in position. This forced out a lot of the cement, but I used it to build up
a layer over the collar split. This was allowed to dry for 24 hours, and
then I lit the fire. That was yesterday and so far all seems ok.
--
Jeff

--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/01/2026 09:40, Jeff Layman wrote:

What nonsense! Are there many surfaces which may be exposed to extreme
heat and are made of plastic?! It also adds "Do not use in metal joints
due to movement & vibration". Despite this, I decided to use it, but reinforce it somehow which would help prevent bits cracking off with expansion movement. I used a small amount of rockwool insulation from
the loft, and mixed it in with the cement. This was then smeared
liberally over the SS flue pipe beneath the crack. I opened the steel
collar crack some more and jammed in more of the cement/rockwool
material. Finally, I fitted a couple of 115 - 140mm SS jubilee clips
over the cracked collar and tightened them until the collar was back in position. This forced out a lot of the cement, but I used it to build up
a layer over the collar split. This was allowed to dry for 24 hours, and then I lit the fire. That was yesterday and so far all seems ok.

Our wood burning stove has a flue coming out of the top. The joint
between the stove and the outer lagging of the flue (*not* that part
that carries the hot gases which I'm sure is still gas-tight) was filled
with ceramic filler. This lasted a few months before crumbling. Each
time we got the chimney swept we got the gap filled again.

This time, we used a different sweep and he noticed that the stove was
able to rock slightly, so he adjusted the legs to make it more stable.
The filler is still perfectly intact; it would have failed by now in
previous years.

So the "do not use in metal joints due to movement & vibration" warning
seems to be very true.
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/01/2026 09:40, Jeff Layman wrote:

"Bostik Fire Cement is suitable for repairs to a wide range of
applications where heat resistance is required, including fire backs, chimney linings, solid fuel heaters, broken bricks in grates & stoves, boilers and other surfaces which may be exposed to extreme heat and are
not made of metal or plastic."

What nonsense! Are there many surfaces which may be exposed to extreme
heat and are made of plastic?! It also adds "Do not use in metal joints
due to movement & vibration". Despite this, I decided to use it, but reinforce it somehow which would help prevent bits cracking off with expansion movement. I used a small amount of rockwool insulation from
the loft, and mixed it in with the cement. This was then smeared
liberally over the SS flue pipe beneath the crack. I opened the steel
collar crack some more and jammed in more of the cement/rockwool
material. Finally, I fitted a couple of 115 - 140mm SS jubilee clips
over the cracked collar and tightened them until the collar was back in position. This forced out a lot of the cement, but I used it to build up
a layer over the collar split. This was allowed to dry for 24 hours, and then I lit the fire. That was yesterday and so far all seems ok.

I think the only issue is lack of stickiness to metal. You could
probably used the glass rope used to seal wood burner doors and wound it
round and smeared with anything that would take the heat.

Or bought an exhaust bandage kit....(e.g. 'gun gum')
--
"When one man dies it's a tragedy. When thousands die it's statistics."

Josef Stalin


--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/01/2026 10:44, The Natural Philosopher wrote:

On 11/01/2026 09:40, Jeff Layman wrote:

"Bostik Fire Cement is suitable for repairs to a wide range of
applications where heat resistance is required, including fire backs,
chimney linings, solid fuel heaters, broken bricks in grates & stoves,
boilers and other surfaces which may be exposed to extreme heat and are
not made of metal or plastic."

What nonsense! Are there many surfaces which may be exposed to extreme
heat and are made of plastic?! It also adds "Do not use in metal joints
due to movement & vibration". Despite this, I decided to use it, but
reinforce it somehow which would help prevent bits cracking off with
expansion movement. I used a small amount of rockwool insulation from
the loft, and mixed it in with the cement. This was then smeared
liberally over the SS flue pipe beneath the crack. I opened the steel
collar crack some more and jammed in more of the cement/rockwool
material. Finally, I fitted a couple of 115 - 140mm SS jubilee clips
over the cracked collar and tightened them until the collar was back in
position. This forced out a lot of the cement, but I used it to build up
a layer over the collar split. This was allowed to dry for 24 hours, and
then I lit the fire. That was yesterday and so far all seems ok.

I think the only issue is lack of stickiness to metal. You could
probably used the glass rope used to seal wood burner doors and wound it round and smeared with anything that would take the heat.

Good point. I've got some spare rope.

Or bought an exhaust bandage kit....(e.g. 'gun gum')

I think from the MSDS that Gun Gum is also sodium silicate - like the
fire cement. Not sure if the bandage has the heat resistance, though. I
doubt that exhausts reach even 300-#C, whereas the fire cement is rated
much higher, perhaps over 800-#C.
--
Jeff
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/01/2026 11:25, Jeff Layman wrote:

On 11/01/2026 10:44, The Natural Philosopher wrote:

On 11/01/2026 09:40, Jeff Layman wrote:

"Bostik Fire Cement is suitable for repairs to a wide range of
applications where heat resistance is required, including fire backs,
chimney linings, solid fuel heaters, broken bricks in grates & stoves,
boilers and other surfaces which may be exposed to extreme heat and are
not made of metal or plastic."

What nonsense! Are there many surfaces which may be exposed to extreme
heat and are made of plastic?! It also adds "Do not use in metal joints
due to movement & vibration". Despite this, I decided to use it, but
reinforce it somehow which would help prevent bits cracking off with
expansion movement. I used a small amount of rockwool insulation from
the loft, and mixed it in with the cement. This was then smeared
liberally over the SS flue pipe beneath the crack. I opened the steel
collar crack some more and jammed in more of the cement/rockwool
material. Finally, I fitted a couple of 115 - 140mm SS jubilee clips
over the cracked collar and tightened them until the collar was back in
position. This forced out a lot of the cement, but I used it to build up >>> a layer over the collar split. This was allowed to dry for 24 hours, and >>> then I lit the fire. That was yesterday and so far all seems ok.

I think the only issue is lack of stickiness to metal. You could
probably used the glass rope used to seal wood burner doors and wound it
round and smeared with anything that would take the heat.

Good point. I've got some spare rope.

Or bought an exhaust bandage kit....(e.g. 'gun gum')

I think from the MSDS that Gun Gum is also sodium silicate - like the
fire cement. Not sure if the bandage has the heat resistance, though. I doubt that exhausts reach even 300-#C, whereas the fire cement is rated
much higher, perhaps over 800-#C.

Exhaust manifolds can easily get red hot.

Glass - esp silica glass- can get to 1500-#C OK.
Although it gets a bit soft in the 900-#C area and beyond
--
"I am inclined to tell the truth and dislike people who lie consistently.
This makes me unfit for the company of people of a Left persuasion, and
all women"

--- Synchronet 3.21a-Linux NewsLink 1.2