I just had the kitchen fireplace remortered. It was so old it was the old burnt crushed limestone mortor and it was just blowing out of the layers. I figure I had my money's worth out of it, it had built in 1882. No, thats not a misprint.
Wanted it to come back looking original. I won't bore you with the story of hows and whys but once it was all done, the applied a coating of this.
It stinks like all get out for a few days but its supposedly what they always use on chimneys to seal 'em up after remodeling.
This fireplace used to be outside the back wall ogf the old house. I started to just tear it down but it just wouldn't been the same come the holidays.
Thats right it was the first stove in the house.....
Still just looks as old as it did, its just functional again and not continiously bleeding motar dust.
I assume if it works on a fireplace, well your grill might be hotter...... <shrugs>