0:05 I have here two different pieces of copper that are from a standard [inaudible 00:09] 0:09 power supply. One common soldering job might be to put a connector on something like this. 0:15 This piece of wire has been stripped and sitting out in the air for a long time and I wanted 0:19 you to see how it looks when compared with something that's just recently stripped. And 0:24 holding them side by side, you can see that the one in my right hand is much, much cleaner 0:29 and shinier. It has a pinkish appearance of nice, clean copper whereas, the one on the 0:34 left not as copper colored. 0:36 The copper that has been exposed to air for a long times forms an oxide layer on its surface 0:41 and that oxide layer tends to disrupt the alloying process of soldering. So it's important 0:47 to be able to get rid of that oxide layer before you begin soldering. 0:51 There are two ways to do that. The first is to mechanically remove it. You can do that 0:56 by using sand paper to abrade away the oxide. And the other way is to chemically remove 1:01 it and for that, we would use our rosin core. 1:04 So let me show you how it looks when we tin solder to the clean copper wire. Begin by 1:11 adding some rosin, placing it in our vice, and heating it with our iron. See the smoke 1:24 forming as the flux burns off and we have a nicely tinned piece of copper. 1:39 Now, if we try to do the same process with the oxidized copper, we're going to run into 1:45 trouble. Add our flux. Okay, here we go. Now, as we heat the joint see that our solder is 1:59 still tries to find its way in there. It doesn't make quite the same contact that we had with 2:05 the other. Just for comparison, I'll hold them side by side. You see little bits of 2:10 brown left over? That's copper that hasn't been properly soldered and the reason for 2:17 that is the oxides that have formed on its surface tend to disrupt that alloying process. 2:21 So in order to make a better solder joint, what we need to do is we need to remove that 2:26 oxide layer. 2:27 What we'll do is we'll cut a new piece of wire. Strip and use our sand paper. Twisting 2:45 the wire. Adding our flux. Applying heat and our solder wicks its way between the wires 3:05 for a nice, clean tinned copper wire. And there you have it.