…if you ain’t got that “plink!” Some bronze and copper clay pieces came out of the kiln fully sintered and some didn’t. Yet they all were fired at the same time. I haven’t done this enough to keep track of where I’ve placed pieces in the kiln to see if that is relevant to which ones sinter and which ones don’t. But, after firing, I have started dropping each piece, from about 2 feet high, onto a table to see if they make that metallic “plink” sound. The pieces that hit with a dull plunk have most likely not sintered properly. These I will tuck in the stainless steel box with my next batch to fire, and I’m pretty sure they will sinter properly when fired again. So far, I can’t tell the difference visually. The earring on the left, below, broke easily when I started to bend it a little. You can see the crumbly brown interior of an unsintered piece of base metal clay. The one on the right made a better sound, and did not start to break, but I will still refire it.
The pieces below seemed to be fine, by the sound of my “drop test.” However, when I polished them with a Scotchbrite wheel, the copper earrings on the top left clearly had not sintered properly.
Come to think of it, the copper earrings above made more of a “thuddy plink” when I dropped them. I though they sounded metallic enough, but it was still a little different than the others. I’ll have to learn to tune my ears to these new bronze and copper clay sounds.
Below are 3 sets of earring components, made with a mix of copper and bronze clay, polished. It’s hard to see the difference between the two metals without applying Baldwin’s Patina to darken the copper. (They all passed the “plink” test!)