In your classroom, or at home, there are many different ways to draw or write things down. You can paint with a brush or color with a crayon. You can draw with a pencil or write with a ball-point pen. Maybe your teacher will highlight something for you using a fiber-tipped pen. It is interesting to look at some of these things to see what they look up close, and maybe figure out how they do what they do.
Looking closely at the tip of the pencil we can see several different materials. Furthest from the point is the paint on surface. This is often yellow. Where the pencil has been sharpened we can see the wood that gives the pencil its strength. Finally, at the very tip, is the lead of the pencil. In the Scanning electron Microscope image on the left we can see the place where the wood (on the left) runs out, and the lead begins. The wood is very rough, and has ridges and shavings on the surface where the pencil sharpener has left its mark. The lead has a very different, much smoother texture. At higher magnification (on the right) we can see that there are little pieces stuck in the overall gray material. The lead is in fact little pieces of graphite stuck in clay. The little pieces of graphite rub off from the pencil to the paper, leaving a mark on the paper; just like using charcoal.
In the Scanning electron microscope the images appear black-and-white, so we don't see the green color of the crayon. What we can see, however, are a lot of tiny scratches on the surface of the crayon. These are made by the paper (or walls) that the crayon has been writing on. They show where bits of wax have been removed from the crayon and are now stuck to the surface of the writing material. The scratches change direction every time you rub the crayon at a different angle. At higher magnification we can see that even though the crayon looks nice and smooth and shiny, it actually has some very tiny texture to it.
The fiber-tipped pen you can see in the image at the top of this page is usually used for highlighting words on a page. Even in the slightly magnified view there you can see a texture running along the shaft of the tip. The texture is made up of lines running parallel to the length of the pen. At higher magnifications in the microscope (about 100 times actual size on the left, and 1000 times actual size on the right), we can see that these lines are actually individual fibers. The images do not look as sharp as some of the other images, and that is because in between each fiber is the ink. It is drawn up between the fibers from a reservoir inside the pen, and left behind whenever the fiber tip touches something - usually a piece of paper. The scanning electron microscope cannot "see" through the ink, giving the kind of image you can see here.
The ball of the ball-point pen is the heart of what makes the pen work. In the picture at the top of the page the ball can barely be seen at the tip of the arrow. The plastic part (where the label "pen" is written) holds the insert which consists of a plastic tube containing the ink and the metal end which holds the ball. The metal end shows up in the image with a bright streak because it reflects light so well. In the magnified image on the left we can see the junction between the metal end (on the left) and the ball on the right. In between is a dark band which is the ink. It oozes through the very thin gap between the metal end and the ball, and covers the surface of the ball. The image on the right is a very high magnification of the surface of the ball, with a small blob of ink still attached.
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Last Update: 5/18/96