A length of old wire has two parts, the copper and whatever was wrapped around it, and both of them keep a record of what was done to them. Nobody writes that record. It is left by heat, by pulling and bending, by weather and years, and by whatever tool last touched it, and each of those leaves a mark the others cannot make. For twenty years I was paid to tell those marks apart, and wire was the plainest teacher I had, because it has so few parts that one mark is never mistaken for another.
Heat
Copper that has run hot is softer than copper that has not. New copper has a spring in it, and a conductor that carried too much current for too long bends afterward with no spring at all, and stays bent. The surface changes color as well. It goes from bright to straw to brown to black, and the color fades out along the wire the farther you get from the hot place, so the shading points at where the heat was. At a bad joint, the joint itself is where the heat was made, and that is where the metal is darkest and the insulation beside it is baked hard and shrunk back from the copper.
An arc is heat of a different kind, and it leaves a different mark. Metal that has been melted and frozen again in an instant does not look like metal that was worked. It sits in a bead, or a pit with a rounded floor, or a tiny ball welded to the end of one strand. Rubber near an arc is charred through in a ring and comes away under a thumbnail.
Strain
Copper pulled past its strength does not simply part. It thins first at one place, draws down to a neck, and breaks there, so the broken end comes to a point, with the strands pulled out to different lengths. That is one pull, hard, and the wire shows that it happened once.
Bending is the other kind of strain and leaves the opposite mark. A cord flexed at the same place over and over goes stiff there, because working copper hardens it, and the cord starts kinking at that spot instead of curving. The strands break one at a time, each on its own day, and the broken faces are flat and grainy rather than drawn. In Dead Short there is an electric blanket that quits all at once, every setting, and Connie finds the break where the blanket was folded the same direction year after year, by bending the crease a hand's width at a time with a meter on it. That is fatigue. It is slow, and it is ordinary, and it happens exactly where the use was.
Age
Weather works on insulation before it works on the metal under it. Old rubber crazes. A hundred fine cracks open before any big one does, and where a cord has lain over an edge for years the cracks run crossways there and nowhere else. The crack edges chalk white. When one of them finally opens wide enough to matter, it wanders, because it follows the weakness in the rubber and not any straight line. The rubber goes hard in a cold barn and will not flex. Tape dries out and lets go of itself. Sockets green up inside where nobody looks. Copper left in the wet turns green, and copper left dry turns a dull brown that comes off on a cloth. None of it is fast. All of it takes years, and none of it happens in one place only.
Dust is a record of time as well. It settles into bands on a coiled cord only where the loops have rested against each other undisturbed, and a cord that has been handled has no bands.
Tools
A tool is the one thing on this list that leaves no record of time at all, because a tool works in a second. A knife opens insulation with walls that are smooth down to the copper and ends that are square, and there is no craze anywhere near the opening, because a cut did not grow. A pair of side cutters leaves a pinched, squared end, and two tails cut together in one bite come off the same length. Pliers print their serrations in the copper. A stripper leaves a ring nick all the way around. Each tool leaves its own mark in the copper, and the copper keeps it for as long as the wire exists.
What a cut lacks is as useful as what it has. Weather never fails in one place alone, so around the opening that finally mattered there is always a neighborhood of small damage that took years to spread. A blade leaves one clean opening and nothing around it. Half of my old job was looking for what was not there.
The order things happened in
A repair made over damage is younger than the damage. Tape wound over an opening was wound after the opening was made, and the grime packed into the tape's weave says how long the tape has been there since. So a wire does not only keep the marks of what happened to it. It keeps the order they happened in, because each one had to be laid down on top of the last. When the tape and the opening under it do not agree about time, the wire has said something that nobody in the room said.
That disagreement is where a materials analyst earns her pay, and it is where a mystery writer earns hers. A finding that cannot be shown in the metal is not a finding, and a clue that cannot be shown on the page is not a clue.
Why the evidence in this book is electrical
Dead Short, my second novel, is set in Gault Mills in December, the first December in ten years that the town's Christmas display will be lit. A lineman named Roland Strom died under that display ten years ago, and the county ruled it an ice storm. Now the council has voted to relight it, and every foot of the old wiring comes to Connie Sadler's bench to be passed or condemned before anyone throws a switch. Nine crates hold a decade of storage, a season of storm repairs, and one string with a county tag on it from the night he died. Under her lamp, the damage on that string has an edge that weather does not leave.
She reads the marks exactly as I have described them here, heat, strain, age and tools, and that is all she has. She is not asking anyone what happened. She is asking the wire, and the wire can only answer with what is in the copper and the rubber. Where those answers agree with the town's account of that night, she passes the string. Where they do not, the damage reads wrong, and she writes down what the glass can swear to, and nothing more.
Dead Short arrives on Kindle this Saturday, November 14, and is open for pre-order now. Every mark the wire keeps is on the page before Connie uses it. If you know what a cut looks like next to a craze, you will be ahead of her for a while.