I plan to use an ornate, framed cast-iron coal furnace door from the early 20th century over a reduced opening on my Grande. The iron frame was made with a slight outward bow, to fit the side of some enormous, coal-fired basement furnace. Once installed, there will be a curved, chord-shaped gap at the top of the frame where it meets the brickwork. How best to close that gap, so all the smoke goes up an equally-ornate cast-iron chimney stack? I really want this to work, because with its gold highlights, the door will be an eyeful.
How big is the gap you need to seal?
Ditto w/ @ kgondoly!
We recommend Grapho-Glass high-temp gasket rope, and they have some rope that is up to 7/8" thick!
It will be crescent-shaped and likely 1.5" at the widest in the center, tapering on either end. The gap will be horizontal, not vertical.