Answer: glass product, oven product or "grandma's recipes"!
There are many possibilities for cleaning an insert or closed hearth window. You can try to clean the glass with ordinary glass product, but it will have to be done while hot. And even in this way, the result is not guaranteed. Otherwise, there is the oven product which works rather well, although it was not at all intended for this purpose at the start. But, in the end, the old "grandmother recipes" remain the most effective solutions! Dip a damp cloth in the ashes of the fireplace and rub the glass with it! Alternatively, soak a cloth this time with a mixture of white vinegar and salt. Then rinse the glass with clear water. The result will be impeccable. Our practical decoration videos