I'm not at the stage of coloring the edges yet but I will surely be carefull not use use to much water.
Edge colouring is important to hide the white paper on cut edges and joins.
Personally, I use marker pens and watercolours. Which type, depends on the subject, and the position of the joint.
Sometimes, I make the edge darker than the print colour, this enhances the join. Otherwise, use a LIGHTER colour than the print, if you want to 'blend' the joint. I say lighter because I have found that the glue darkens the hue slightly. I aslo colour the tabs along the colour edge too.
As you correctly stated, do not use too much water when edge clolouring with watercolour pencils. The edge soaks up the moisture real quick, and when you run the pencil along it, the action will turn the edge to mush. The technique I use involves letting the TIP of the pencil soak in water for about 15 seconds, shake the water off, wait a minute, then colour the edge. BE CAREFUL as you apply, the tip of the pencil will be soft and release a lot of pigment quickly as a paste. I then lick my finger, or thumb, and GENTLY run it along the edge to blend the pigment into the fibers of the paper. I then lick my thumb and finger and run the paper between my thumb and finger, using gentle pressure, running away from the edge. See motion depicted in the photo.
This helps to sharpen the edge and also remove any excess pigment on the print. The amount of moisture you need with your 'lick' depends on the print ink type. You want just enough to allow the moisture to pick up the excess pigment in your fingerprint, so to speak, but not damage the printed surface. The technique does work better on satin or glossy paper.
Repeat the process as necessary. Of course, you could use a DAMP cloth to moisten your fingers instead of your tongue (I walked around the city for 2 hours a few months ago, with a blue tongue.

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Reload the tip of the pencil with moisture as required.
Remember, you want the majority of the moisture in the pigment,
not the paper.
But, my best advice: PRACTICE!!!!! Until you get the feel for it.
Good luck, and dont be afraid to ask!! :mrgreen:
Oh, one other thing, edge colouring does add a heck of a lot of time to the build process, especially on intricate designs, as I well know with my current project: :mrgreen:
http://www.zealot.com/forum/showthread.php?t=173891
See you around the Forum.
