Although this does look like a greyish-black blob, it actually shows a technique I have discovered and I love. As always, click on it and it should enlarge for you. Hopefully it will show enough detail so you can see.
How did I do it? I started with a piece of white cardstock, which I then 'painted' with a fairly uniform coat of white glue (you aim for a nice coating, but not too thick). I then proceeded to my laundry tub where I had easy access to water! Put a candle in a substantial holder (see now why I suggest being close to water?) and I put it right into the laundry tub for safety. Then you simply run the wet glue side of the paper over the candle flame until it turns black and bubbly. I tried to vary the distance I held it over the flame in order to vary the coloration in the finished product. Set aside to dry. I think my coating of glue was a trifle too thick because it did take quite awhile to dry. The instructions I worked from said that you should wipe any soot off afterwards, but I found my piece didn't have any. I think it would make a fun background for an atc or any piece of artwork.