Toolsday: On Tape

There are many different kinds of tape. Because people use tape for many many different things.

Knowing what you want to do with tape is the key to using the right tape. Are you trying to hold something together? Or mask something off? Hang something up? Or stick something down? All different kinds of tape. So here’s a post about one kind of tape, and there will be more posts about other kinds of tape.

Electrical tape.

You need this if you are doing any sort of electrical work. It’s vinyl, usually 3/4″ wide, and usually black. You use it to cover any sort of electrical joint to keep it insulated. Many electricians will wrap a layer of tape around the outlet or switch after the wires are connected to keep the screws from shorting to anything else in the box. And usually around the base of all the wire nuts to keep them twisted on and extra safe.

When you go to the Big Box Home Center, you will find that there are a few different brands of cheap black electrical tape, including 3m’s budget line.

I hate them all.

The adhesive on black electrical tape is black. And it doesn’t stay on the tape. So if you have to go back in for anything there’s black goo everywhere, even after just a few days.

The adhesive on 3m’s more expensive colored electrical tape is not black. And it stays on the tape mostly. This is the stuff I generally buy. It comes in 9 colors. If you buy more than one color you can also use it to help remember which wire is which.

(There are historical reason why it comes in 10 colors (including black), having to do with the history of telephones:

Every phone line needs a pair of wires. And a phone cable might have many many pairs of wires inside. So how do you tell them apart? Color coding! Ma Bell came up with a system of color coding in the 40s that lets 10 colors sort out a virtually infinite number of wires. The ten colors are divided into 5 “tip” colors (White, Red, Black, Yellow, and Violet), and 5 “ring” colors (Blue, Orange, Green, Brown, and Gray (Called “Slate” so that each color in the group of 5 has a unique one-or-two-letter abbreviation: W,R,BK,Y,V, BL,O,G,BR,S). So a pair of wires will consist of a wire that is mostly a tip color, with stripes of a ring color, and its other half which is mostly the ring color with a stripe of the tip color. For instance Yellow with Slate and Slate with Yellow. And the pairs are thus in numerical order from White/Blue all the way to Violet/Slate. And once you know the code, you can figure out that the Yellow/Slate pair is pair number 20.

So that gets us up to 25 pairs (5×5). After that, you wrap that 25 pairs in…a White and Blue string! The next 25 pairs are wrapped in a White and Orange string. Etc. So that gets us up to 25×25, which is 625 pairs, or 1250 individual wires. But to make the math easier, they stop at 25×24: 600 pairs. You can go on from there, wrapping that whole bundle in a white and blue string. And so on. But it’s already ridiculous…In any case, that’s why the electrical tape comes in those particular 10 colors: so that phone people can use it to mark things in a standardized way.)  (incidentally, that’s also why phone company boxes and stuff are that special greenish gray: that color is not Slate. So things like zip ties and the like that are that color are not mistaken for color-coding markers…)

Electricians use a different color coding scheme; theirs is all about what’s on the wire rather than which particular wire it is. But that’s not relevant; electricians mostly don’t pay attention to the color of the tape. They mostly use black. But as I said I don’t like the black because it tends to leave its goo everywhere. I buy a different color roll every time I buy some.

Electrical tape tends to get stiff after a few years (especially the cheap stuff), and it doesn’t stick very well to things that are not metal or plastic. So it’s not good for doing things like taping up packages. But you need some around if you are ever going to do electrical work.

When taping over a splice, use enough. You should start a little ways back from the joint, and wrap it around and around, layering about half the width of the tape each time so at every spot on the repair there is at least two layers of tape. On the other hand, it’s certainly possible to use a stupid amount of tape and make a repair that is no safer than the right amount of tape, and may be less safe just by being a bigger lump to snag on things. Use prudence.


A guy in his early 50s, living more or less alone in a 90-year-old house, trying to keep it all together.

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Posted in History, Tools, Wires
5 comments on “Toolsday: On Tape
  1. Star Straf says:

    I actually have this skill – Friend of ours taught me how to change out switches and outlets and yes he taught me about wrapping the tape around the box. I was able to change some cause they were ‘soft’ and some for color coordination, even did an advanced version of 3-way switches. Got stalled in that project still have a dozen or so to do.

  2. Deb Kosiba says:

    “it doesn’t stick very well to things that are not metal or plastic.”

    Frankly, it doesn’t stick all that well to metal or plastic, really. For that matter, it doesn’t stick to itself all that well either. In my book it only has one use, and that’s for electrical stuff that will be shoved in a box or wall and won’t be subjected to any movement or handling. And for those uses, shrink tube is better.

    • Erik says:

      I have not ever had it stop sticking to itself. Or to plastic, like a wire nut or the plastic of an outlet block.
      And shrink tube is not appropriate for (for instance) wrapping all the way around an outlet to cover the exposed wiring screws. Shrink tube is better for most inline splices. But it’s also a lot harder to master. The home repair person just starting out is going to get better results from electrical tape.

  3. Sam Paris says:

    I didn’t know about the colored 3M tape–I mean, I’ve seen it, of course–but I didn’t know it was better quality than that wretched black stuff. Thanks for the tip! I shall order some from Amazon post-haste. (Yes, of course I’ll use your link.)

    I didn’t know about Ma Bell’s color code, either, other than green and black for tip and red and yellow for ring. The guy who told me about it (a retired Bell repairman who was more than a little tipsy at the time), actually looked around and lowered his voice before explaining it to me, as though he was divulging a state secret. This would have been sometime in the early seventies, when The Phone Company’s disapproval of unauthorized extensions still had teeth.

    • Erik says:

      Yes. The RGBY colors are a totally separate thing from the 10-color code. I encounter them so seldom that I usually have to look up the Black/Yellow order. (Red is Ring is easier to remember.)

      The phone company’s problem with unauthorized extensions was mostly marketing/sales, and a little bit engineering: Back then, the phone’s bells drew a hefty current, and there was only so many ringers a standard line could support before the bells started ringing too faintly. That number is about 5, it turns out, on a nice clean line not too far from the CO. So if you were to hook up a bunch of extra extensions, they’d start overloading the equipment back at the CO, and also they wouldn’t ring. If the phone installer encountered this problem, he could adjust things, double up pairs going back to the CO (for more current), add a booster, etc. But you the home user don’t have access to that stuff.

      If you look at a modern landline phone, either on the phone or in the documentation, you will find its “REN” (Ringer Equivalence Number). With a modern phone with a non-mechanical ringer, that number will be very small; I’ve seen RENs anywhere from .1 to .05. In this modern deregulated world you can hook up any number of phones that you wish to your line as long as all the RENs add up to less than 5. But no one ever pays attention to RENs anymore, because at .1 per, your average user would have to be doing something very odd to get to 5 RENs.

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