1. Black Pencil Cores Are Made of Graphite and Clay
The core of a black pencil is made from graphite and clay. The ratio in which these two materials are mixed determines the hardness, labeled as H or B [1][2]. Graphite has a structure of thin, overlapping layers that slide easily against each other, which explains why writing feels smooth [4]. The color of graphite is a blackish-gray with a slight lead tint.
After the core is shaped, it is fired at high temperatures of over 1000°C (about 1832°F) [5]. However, graphite can only produce black to gray colors. To create red or blue colored pencils, different base materials are required.
2. Colored Pencil Cores Use Pigments, Wax, and Talc Instead of Clay
Colored pencil cores do not use clay. Instead, they are made from pigments to create color, talc and wax to improve writing texture, and adhesives to hold the mixture together [1]. The Japan Pencil Industry Cooperative also explains that colored pencils mix dyes or pigments, talc, wax, and other materials, without using clay [2]. Both organizations describe the composition in generally the same way.
In black pencils, graphite serves both as the "black color" and the "writing core." In colored pencils, there are mainly materials for creating color and materials for writing texture and hardening the core. This means that to change the color, manufacturers simply swap out the coloring material. The specific ratios vary by manufacturer and color. One reference notes an example where talc makes up about half of the mixture, but this is just one example [11].
3. Colored Pencil Cores Are Dried at 50°C for About 3 Days, Not Fired
To make colored pencil cores, water is added to the raw materials and mixed. The mixture is extruded to the thickness of the core, cut into lengths of about 20 cm (about 8 inches), and dried in a machine at 50°C (about 122°F). According to Mitsubishi Pencil, the drying time averages around 70 hours [3]. Seventy hours is nearly 3 days, though "average" means the time is not always exactly the same.
The major difference from black pencils is that colored pencil cores are not fired in a furnace [2][3]. Mitsubishi Pencil states that because they are not fired, the cores remain soft. The method of hardening the core is different from that of graphite pencils.
4. Pigments Give Colored Pencils Their Color Because They Do Not Dissolve
Color sources are divided into dyes and pigments. Dyes dissolve in solvents, while pigments do not. Pigments are used as small particles scattered throughout the core without dissolving [6]. Mitsubishi Pencil explains that colored pencils use pigments because they offer better color vibrancy and lightfastness than dyes [7]. Lightfastness is the property of resisting color change when exposed to light.
However, "pigment" does not guarantee that a color will never fade. The company notes that for some colors, pigments with lower lightfastness are intentionally chosen to preserve the specific hue, even if they fade faster than other writing tools [7].
5. Layering Colored Pencils Makes the Colors Look Mixed
When mixing colors with colored pencils, Sakura Cray-Pas explains that you are not blending them like paint. Instead, you are layering them. The fine color particles that land on the paper surface appear mixed to the human eye [9]. The appearance also changes based on how hard you press. With light pressure, you can apply color thinly; with strong pressure, you can apply it darkly. However, pressing too hard can dent the paper, making it difficult for colors layered on top to adhere later.
Sakura Cray-Pas also notes that holding the pencil upright allows color to enter the dents in the paper, while laying it on its side makes the paper texture more visible. The basic rule is to start applying light colors first [9].
6. Why Colored Pencils Are Hard to Erase: Wax Soaks into Paper
Returning to the initial question: why are colored pencils hard to erase? QuizKnock cites a Mitsubishi Pencil representative who explains that graphite sits only on the surface of the paper, so it is easily removed by an eraser. The representative explains that in colored pencils, the wax melts and soaks into the interior of the paper. This makes the core incompatible with the eraser, causing it to resist removal [10]. Wax is a material not found in graphite pencil cores. The source does not explain why the wax melts.
Thus, the difficulty in erasing colored pencils is explained by the difference in core materials. Note that watercolor pencils are made to dissolve in water by adding emulsifiers or similar agents, allowing them to be blended with a wet brush. Regular colored pencils are oil-based and do not dissolve in water [11].
7. How Colored Pencil Fading Varies by Color and Line Thickness
Mitsubishi Pencil states that the degree of fading differs depending on the color and the thickness (density) of the drawn line. They note that if a colored pencil drawing is left in direct sunlight, the colors may change enough to look like a different color scheme within a few years [7].
In Japan, the JIS (Japanese Industrial Standards) S 6006 sets rules for colored pencil cores. The standard colors are 48, with specific criteria for hue, brightness, and saturation, as well as allowable ranges. Lightfastness is required to be Grade 3 or higher (Grade 2 or higher for some colors) [8]. The standards do not specify the exact pigment composition. Note that these 48 colors are the standard number in the specification, which is different from the number of colors sold in stores.
8. An Experiment: Comparing Erasing with a Black and a Red Pencil
Try drawing lines of the same length with a black pencil and a red colored pencil on the edge of a paper. Use the same eraser with similar force to compare how they erase. Next, apply yellow first, then layer red on top. Vary your pressure from light to strong to see how the darkness changes in the same spot. If you have a magnifying glass, you might see the color particles entering the texture of the paper.
Results may vary depending on the paper and eraser used. Do not judge by a single test; try it several times. Be careful not to point or swing the sharpened tips of colored pencils at people.