Photography and commentary by Paul Yarnall

Shaky CD’s…. or What’s Buzzin’?

Yeah, I know… this is supposed to be a photography (and related) blog and so you are asking yourself, “what does shaky CDs have to do with photography?”. Well, the computer is the nerve center of photo processing and most of us have stored or transferred images via CDs, and now DVDs too, so you see, it is related.

A friend brought over some files for me to work on the other day on a CD and since Murphys Law was in full swing that day I could not read some of the files. I was also thinking that my PC was making some nasty sounds it doesn’t normally make. After ejecting the disk (the source of the noise)I noticed that it was labeled with a standard run of the mill 1×3″ self adhesive label about an inch from the center of the disk.

Hmmm… could that little label be the source of the noise and the reading problem? After all how much can a paper label weigh? Well, it’s not much. .00033lbs to be precise, give or take a couple of 10 thousandths. (Yes, I weighed it.) In my other life as an engineer I keep some formulas handy in my spreadsheet program and one of them calculates centrifugal force. Let’s see how “heavy” a little piece of paper is at the 5000-10,000 RPMs, (no, that is not a typo), that a typical CD spins at now days.

This calculation finds the centrifugal force of a mass spinning around an axis…. think of a soft ball on a 6′ rope that you start swinging around over your head. The ball starts getting “heavy” as you swing faster and faster. Well, our little bitty piece of paper exerts a radial outward force of just under a quarter of a pound (like the heart attack hamburger) at 5000 RPMs, and just under 1 pound, (a loaf of good bread), at 10,000 RPMs. Yikes! No wonder my CD drive was making noises. That is a very large imbalance and the result is a lot of vibration. (If the label was 2″ from the center the forces would double!)

Guess what? After I removed the label the drive became silent again and I could now read the problem files. Amazing. (Yes, I loved Mr. Wizard as a kid. If you don’t know who that is, young fellar, Google him.)

So what are the best ways to label our CDs and DVDs? Some of the printers on the market now have disk printing capability. They need disks with a special surface coating for the inks to adhere to, but aside from that, if you have one of those you’re good to go. For the rest of us, Sharpie makes felt tip pens made just for CDs use solvents which won’t attack the plastic. I have gotten away for years using their standard permanent marking pens, which may not be approved, but I keep the writing in near the center when possible. (If you are using the premium quality archival gold disks, such as the Delkins, you should probably use the approved pens). Verbatim and Avery both make circular labels that are self adhesive and can be run through a printer if desired and are then applied with a little fixture they provide to make sure the label stays centered. Personally, I am not that motivated, but hey give it a go. What ever you do , don’t use a ball point pen as there is a good chance that the data layer can be damaged.

I bet you never thought much about CD labels before all this. You can thank me later!