Copic makes a thick white paint, called Opaque White. This is great tool to add final touches to any work. When working with markers, it is usually best to start light and go dark, mostly because it is easier to leave an area white than to try and fade it back out to white with a colorless blender.
However, sometimes the white touches you want to leave are so small that it would be next to impossible to leave them white. Some people use a white colored pencil to add final highlights into their work, but a colored pencil is not always as opaque as you need it to be. This is where Copic Opaque white comes in.
Opaque White is a very thick, water based paint that works best when applied with a fine paintbrush or toothpick. Being waterbased, you can thin it if you need to, but I prefer it thick for best opacity.
Here are two drawings of a grove of redwood trees (for a complete tutorial, click here)
This is a very nice picture by itself, but because the image is so small, it is hard to leave any areas white. This is where the Opaque white comes in.
By adding white back into my work it changes the feel of the image. Notice how the branches and trunk of the foreground tree seem to stand out more simply by adding the opaque white.
The branch clusters are catching the sunlight more, and you can tell that the trunk is wrinkled and has depth. I thinned the paint in a few spots on the trunk to lighten some areas less than others. Now that I have added white, I can't add marker, as the opaque white absorbs ink differently than paper and it will look strange.
Is the second tree example better than the first image? No, it is simply different. You may prefer it with the white or like it better before white was added.
Here is another example of Opaque white. I drew this scooter, leaving some areas white, but still, I needed to add the final reflective highlights.
Opaque White allowed me the precision and opacity to quickly and easily finish my piece.
Since this picture involves a lot of reflective metal, the scooter definitely looked flat and lifeless without glints of light reflecting off the chrome and shiny paint.