I talked about the ting sound that you hear to indicate that the clay has turned to metal. The first time it was unmistakable. Sometimes it’s not quite as obvious and I have to test the bead a few times to make sure that I’m really hearing a ting.
When the piece stops flaming, you know that the binder is burned off. But, it still takes a few minutes of firing to sinter completely. No ting means that it’s underfired and isn’t completely sintered. And if it’s underfired, it can crumble! At that point, you have half-fired metal (not clay anymore) so it’s not even good for glue.
So, how do I make sure that I don’t underfire it? Basically, I err on the side of caution and make sure that the bead is absolutely glowing before I start my timer. I also fire with the lights off so that I can really see the glow and make sure that it maintains that glow for the entire time. I probably risk overfiring the bead, but at most I’m overfiring it for 10-20 seconds, so I think the risk is small. And I still always make sure that it’s an even, glowing heat and that it never gets “angry red.” If it gets too hot, you can melt it (I’ve melted part of one bead so I know what “angry red” looks like) but I haven’t seen any consequences of keeping it at the right temperature for just a little longer than it needs to be. I’ve been tempted once or twice to put a bead back under the torch after it’s cooled, but usually a few drop tests and I can hear the ting. And so far none of my beads have crumbled.
Of course, all of my experience is with silver clay. I’m a bit concerned about the copper clay once I start trying it. I’m not sure why copper clay is trickier, but I have heard of people (who have experience with silver clay) having issues with underfired copper clay.
Note: that’s not actually underfired clay in the picture, just my interpretation of what would happen to a bead if I underfired it :)
Do you err on the side of caution with anything that you do? Or do you throw caution to the wind?