Reading your bead: good, cold, and burned-through
Alright. So we've done the ground clamp, we've done wire, we've done matching your settings, gas, stance, the arc, slowing down, running a straight line. That's the whole setup and technique stack. Now we get to look at what actually came out the other end.
This is the lesson where you flip your helmet up, look at the bead you just laid, and figure out what it's telling you. Because it is telling you something. Every bead is basically a little report card on your settings and your speed, and once you learn to read it, you stop guessing.
I feel like this is the part beginners skip. They run a bead, it looks... fine, I guess, and they move on to the next piece of scrap without ever really looking. I did that for weeks. Didn't know what I was looking at, so I didn't look very hard. Don't do that. Slow down at the end too, not just during.
The three beads you need to recognize
A good bead looks like stacked dimes. Little consistent ripples, evenly spaced, all about the same size, laid in a straight line. It'll have a slight shine to it once it cools and the color should be fairly even along the whole length. When I finally got one that looked like the videos, I called Jan out to the garage to come look at it. She said it looked nice. I was thrilled the rest of the day. That's genuinely how exciting it is the first time. Don't let anybody tell you that's a silly thing to be proud of.
A cold bead sits up high on the surface like a fat rope, and it doesn't tie into the metal on either side. You can sometimes see a little lip where it just kind of... rests there instead of melting in. Tap it with a chipping hammer or scratch at the edge and it can flake or pop right off, because it never actually fused. Cold welds usually mean your heat's too low, your amperage or wire speed is set wrong for the thickness, or you moved the gun too fast for the heat you had. It looks like a weld. It is not a weld. It's glue that happens to be made of metal.
A burned-through bead is the opposite problem. You'll see a hole, or the metal warps and puckers around the weld, sometimes there's a divot where metal that should be part of your joint just dropped through to the other side. This is heat that's too high for the thickness you're working with, or you moved too slow and let it sit and eat through. I know this one personally. I tried to weld something too thin once, blew a hole clean through it, and then spent an hour trying to fill the hole, which just made bigger holes. That's a bad hour. Match your settings to your metal thickness before you strike the arc, not after you've already got a hole to explain.
How to actually check what you've got
Here's what I do, every time, on scrap:
- Look at it cold first, no touching. Ripple pattern even? Sitting flat, not piled up? Color consistent, no dark burnt patches or shiny unmelted patches?
- Flip the piece over if you can. On thinner metal you'll often see the back side has a little bit of penetration showing through, a slight bump or discoloration following the weld line. That's usually a good sign. If you see nothing back there at all, that's leaning cold. If you punched clean through, that's obvious.
- Tap it. A wire brush or a light tap with a hammer on a good weld does basically nothing. On a cold weld you can sometimes get flaking or chipping at the edges. Don't go beating on it like you're mad at it, just a firm tap to see if anything moves.
- Try to break it if it's scrap you don't care about. This is the best teacher there is. Clamp it and bend it, or whack it with something. A good weld tears the metal around it before it lets go. A cold weld just pops apart clean, like it was never really attached, because it wasn't.
Do this on every practice piece for a while. It feels slow. It's how you build the eye.
I'll say this too, since it fits right here: I think setup is where beginners actually fail, not the welding part. If your ground's solid and your settings match your metal, the bead pretty much runs itself and what you're checking here mostly confirms that. When people get a bad bead they usually blame their hand technique first. Check your settings first. Hands are usually fine.
Quick aside, nothing to do with welding really, but I went up the canyon one morning a while back to take some pictures, got this shot of the ridge line that I really loved, the light was doing something I hadn't seen before. Posted it a few places. Two likes. Brought it up at dinner hoping somebody'd say something. Nobody did. Anyway. The point is, sometimes you know a thing turned out good and nobody else has to confirm it for you to know it. Same with a bead. You'll know when it's right before anybody tells you.
Before next time
Run five beads on scrap, then deliberately try to break two of them. See what a real weld feels like when it fails versus what a cold one feels like. That contrast is worth more than anything I can describe to you here.