I did not think of this idea. I got it off gimpology.com .Ok I've made an instructable for creating fire writing, but I didn't tell you how to make the fire. all I told you was to use an image so this instructable will tell you how to actually create the flames from scratch. For the easier one click Banana's.
Step 1: Opening a New Image
Okay, now alot of people tell you what size to use for your image but it doesn't matter, I use 640 by 400 pixels. Once you have a blank page bucket fill it black.
Step 2: Text
Next step is to write in your text. For some bizarre reason I wrote GIMP in capitals? you don't have to though
Step 3: Preperation for "The Smudge"
Ok so this is a short as step but who cares there's no law against it! Select the smudge tool and set the settings the same.
Step 4: "The Smudge"
There are several things you will need to do in this step,
The first is: Layer -> Layer to image size.
Next: enlarge the picture 2 or 3 times and smudge as in picture 1
Lastly(Is that a word?): Make the flame like motion in picture two.
Do this with all the letters.
Step 5: Final Step
Now what's a fire without colour? nothing so we gotta add some.
First merge the fire layer with the background(right click the fire layer in the layers box and click merge down)
Then click: colour -> colour balance.
Use these attributes: Shadows 100,30,-30