Black on outside of insert glass?

[johnblacksox]

I have a Lopi fireplace insert that I've been using for 5 years now. I use it nightly in winter, more for ambiance than for heating my house.

This week, I noticed a patch of rough black marks on the outside of the glass. It's about 3 inches by 1 inch, and it looks and feels like the top of creme brule', as if something like sugar was burnt onto the outside of the glass.

Now, some details...

- Nothing ever comes anywhere near the glass, so no chance I accidentally brushed against the hot glass with some material.
- I don't burn crazy hot fires. I use bone dry wood, and I only burn for like 4ish hours a night.
- I clean the inside of the glass regularly, and it stays nice and clean.
- I tried scraping the black mark with my fingernail, and nothing came off. I tried a wet cloth and nothing came off. I haven't tried glass cleaner yet.

It's almost like the outside of the glass burned. But again, I've been burning fine for years, and my fires are absolutely not crazy hot.

Any ideas what happened here?

Thanks...

 

[begreen]

It sure sounds like something brushed up against the hot glass. Check polyester and nylon pant legs, pet's fur, etc.

 

[johnblacksox]

Hm, I can't imagine how that could have ever happened, but yeah, I can't think of any other possibility.

If that's the case, how do I get it off? Razor blade?

 

[EbS-P]

carefully use the blade. Then I just let the rest burn off.

 

[stoveliker]

You can round the corners of the blade if you're concerned about scratching the glass

 

[johnblacksox]

Update: I burned a long hot fire last night, and today, at lot of the black on the outside of the glass has burned off. There's some slight ash there. So I think I can forget the razor blade, and it will eventually go away on its own.

 

[30WCF]

My wife had on a knee length puffy coat and bent down to clip a leash on the dog near the front door (and stove) to take the pooch out for the PM pee. When she bent over the long coat lifted in the rear and hit the glass. Looked
Like black paint with brush marks on the glass.