Old copper wires have cracked insulation, what's the risk?

Risk of electric shock if you touch the exposed wires, especially if they're wet, and there's also the possibility of a short circuit that could cause a fire. You should replace that wiring as soon as possible for safety.

I've already had this problem at home and it was pretty concerning - I found some old phone wires with the coating falling apart in a corner, leaving the copper completely exposed. The worst part is you can't really tell what condition they're in if they're hidden behind furniture or coiled up. What happens is when the insulation goes away, any contact with moisture (condensation, cleaning, even sweat from your hands) creates a path for current to flow through your body if you touch them. But there's a second risk that's maybe even more dangerous.

When bare wires sit together or very close to each other, especially if there's dust or dirt wrapping around them, the electrical resistance at the contact point gets really high, generating concentrated heat. This can simply start melting whatever coating is left and eventually ignite the material around it - it doesn't even need to be a proper short circuit, just that hot spot kept going long enough. If those wires are in walls, behind wood, or near other flammable stuff, the risk is serious.

The short-term fix is to insulate them properly with quality electrical tape (the cheap stuff doesn't last), but if the coating is really compromised, tape is just a band-aid. The right thing to do is replace the wires or at least that deteriorated section - if you can identify exactly where they are and what they're for, take photos before you do anything.

It really depends on where those wires are and whether they're carrying current. If they're old deactivated wires, the risk is lower, but if they're still connected to the grid, the exposed copper can create a point of weak insulation that makes both electric shock and electrical arcs more likely, especially if there's moisture or if someone happens to touch them. The worst part is that a crack in the sheathing won't warn you - you might not even notice it's dangerous until something actually happens, so if you see wires like that it's really better to get them fixed right away.

I saw wires like that in an old apartment where I was doing some work, and the electrician said that besides the obvious risk of fire and shock, the cracked insulation lets moisture in, which corrodes the copper and makes the condition even worse. If it's connected to the grid, call someone to replace it right away.

Don't tackle this on your own, first of all. Bare copper and electrical current is a dangerous combination, and the risk changes depending on the situation. If the wires are still active (connected to the mains or something with voltage), you have a real risk of shock if you touch them, especially with wet hands or in a wet spot. Exposed copper also creates localized resistance that generates heat, and yeah, it can lead to fire if there's enough current flowing through it.

Now, what nobody mentioned: wires with deteriorated casing in walls or enclosed spaces are even more dangerous because they accumulate moisture and dust, and that degrades the insulation further. If they're tucked inside conduit or next to other cables, the heat gets concentrated and doesn't dissipate. What looked like a localized problem can damage your entire electrical system.

If there's still current running through them, call an electrician. If they're old wires that are actually abandoned, get them out of circulation and dispose of them properly - don't just leave them there. The thing is, cracked casing is a warning that the wire has reached the end of its useful life, regardless of the immediate risk.

It's not so much that exposed copper by itself is dangerous - the real problem is when there's moisture or accidental contact, that's when it becomes a serious shock hazard. What nobody mentioned is that old wires with this kind of deterioration usually have the entire insulation compromised, it's not just the crack you can see - it might be fragile inside too, so any movement or vibration can make it worse and expose more of the wiring.

Those answers get the main risks right, but there's one detail missing: a crack in the insulation doesn't necessarily mean the wire will catch fire or shock you right away. It all depends on the current flowing through, how humid the place is, and whether there's actual accidental contact. The real danger is when you leave it like that for too long - it starts to oxidize, corrosion gets worse, and then the resistance increases and generates heat. If the wires are live and connected to the grid, they really do need to be replaced soon; but if it's in a dry place that's hard to get to, you've got more time to fix it than it might seem.