A kneaded eraser looks suspiciously like a lump of putty, but that's exactly what makes it useful. Unlike a traditional eraser that rubs across the paper, a kneaded eraser can be shaped, pressed, rolled, and dabbed to lift small amounts of pigment.
That's particularly useful with colored pencil, where completely erasing a dark area can be difficult or impossible. Instead of thinking of a kneaded eraser as an undo button, think of it as another drawing tool. It can soften an area that's become too dark, recover a highlight, reduce harsh pencil marks, or lift just enough pigment to let you work over an area again.
Before using it on a finished page, knead the eraser between your fingers until it's soft and pliable.
Then try changing its shape.
Roll it into a ball for larger areas. Flatten it into a soft edge for broader lifting. Pinch it into a tiny point for details. Roll it into a small cylinder when you want to lift a narrow strip.
That's one of its biggest advantages: you can make the eraser fit the mark instead of trying to make the mark fit the eraser.
On scrap paper, create a fairly dark patch using several light layers of colored pencil.
Now divide it mentally into four sections.
On the first, press and lift the eraser straight upward.
On the second, dab repeatedly.
On the third, gently roll the eraser across the pigment.
On the fourth, try ordinary rubbing.
Compare the results.
You'll probably find that pressing and rolling give you much more control. Vigorous rubbing can disturb the paper surface—and colored pencil generally responds better to persuasion than combat.
Here's where a kneaded eraser becomes especially fun.
Color a simple sphere, apple, ornament, eye, glass bottle, or other rounded object. Build enough color that you have a reasonably dark middle value.
Pinch your kneaded eraser into a small point and gently lift pigment where the light would strike the object.
Don't try to make the area completely white. Lift a little, look at it, and repeat if necessary.
Suddenly you've created light after coloring the area rather than having to perfectly preserve that highlight from the beginning.
That's a handy trick to have when your pencil gets enthusiastic before your brain catches up.
A kneaded eraser absorbs graphite and pigment as you use it. When the surface becomes dirty, stretch it, fold the dirty portion inward, and knead it again. A cleaner surface will emerge.
Eventually the entire eraser becomes saturated and stops lifting effectively. That's when it's time to replace it.
Keep it in a small container or wrapper when you're not using it. Otherwise, its remarkable ability to pick things up will extend to dust, crumbs, cat hair, and whatever mysterious substance happens to live at the bottom of your art-supply drawer.
Kneaded erasers work best on lighter applications of colored pencil. If you've applied many heavy layers or burnished the surface, much of that pigment has been pressed firmly into the paper and will be harder to lift.
That's another reason to build colored pencil gradually: lighter layers leave you more opportunities to change your mind.
Lift a little at a time. You can always lift again; you can't put the original pencil stroke back exactly where it was.
Use your kneaded eraser gently and deliberately. It's less about removing your work than giving yourself another opportunity to shape the light.