Sparkling Fireplace Glass - cooking recipe

Ingredients

1 cup wood ash
4 cups water
window cleaner

Preparation

IMPORTANT NOTE: after posting this recipe, I tried another time and was disappointed in the result. An additional important step for this to work is to do this while the glass is still warm from a fire. The creosote is softened at this point and it will wipe off easier.
Prep: lay down newspaper if you are worried about sludge dripping on your floor. Our area is all brick or cement so it isn't an issue for me. Wear gloves! I got lazy the last time and my hands are still recovering. Use a sponge with a scrubber that is about to be thrown out since it will be black beyond repair when you are done. I have had some light scratching from the scrubber so if you are concerned, use one that has the plastic scrubber for teflon.
Do NOT clean the inside of the fireplace first. You need the ashes that are inside!
Fill a bowl with plain warm water. Only use plastic if you don't care about it getting dirty.
Wet the sponge in the water. Dip the scrubber side into the whitest ashes of the fireplace. Rub the scrubber lightly over the black, baked on glass. I've noticed that it works best if you let that first application set for several seconds and then scrub it. You will see a bunch just melt off. There will be more that takes more scrubbing. Use the water to rinse the sponge occasionally and redip the sponge in the ashes as needed. I find the water has to be replaced with each pane of glass.
After you feel that the pane of glass is clean you will have to spray it with window cleaner and wipe with a paper towel, otherwise there will be a cloudy film left behind.
Double-check that you didn't miss anything since the cloudy film can mask some spots the first time.
Why does this work? It turns out that lye is made from wood ashes -- hence the reason to wear gloves!