Why Anneal

When I was a kid, fried marble jewelry was big. I doubt many of my readers remember the gawdawful bracelets and necklaces we made using fried marbles, but I remember with particular pride a lime-green bracelet I made all on my very own when I was maybe eight or nine.

One fries marbles by heating them in a frying pan (without oil) and then, while they are still hot, dumping them into a bowl of water. The stress of the sudden drop in temperature causes tiny fractures to occur through the marble, making it all crazed and sparkly. The fried marbles were then glued into bracelets made specially for marbles.

Of course, frying marbles weakened them, and eventually your marble masterpiece would break. That’s the reason I no longer have my lime green masterpiece; two of the marbles knocked against the swing when I was at recess one fine day and shattered beyond recall. Bear with me – this is actually going somewhere.

When you make beads the way I do, you melt the glass and wind it onto a steel rod that has been treated with a special clay-like substance to make it let go of the bead. Once the bead is finished, I have to let it cool enough so that it forms a “skin” and will hold its shape, and then I put it between two thermal “blankets” and let it stay there for an hour or so. While the resulting beads look fine to the naked eye, this is like taking a marble out of the frying pan and dumping it in water. Tiny micro-fractures develop in the beads because they cooled down too fast for the glass molecules to figure out how to play nice with each other. Little areas of stress develop in the glass where it cooled down unevenly. Over time, in some beads, these stress areas will lead to larger cracks, and eventually the bead may break.

The way to protect a bead from future breakage is by annealing it to remove all the tiny fractures and stress points that developed from the too-rapid cooling down process. Annealing realigns the molecules of glass in the bead so that they more happily associate with each other. The way to do this is to bring the bead up to just below its melting point, and then drop the temperature very, very slowly. The micro-fractures in the bead will meld back together, and the stress inside the bead will be relieved.

I drop the temperature on the beads by a degree a minute, which sounds like a pretty rapid drop until you factor in the fact that I bring the beads up to 925°F (about 500°C). It will take them an hour or so to get up to temperature, and then another 14 or so hours to come back to room temperature. Even this will not guarantee that the beads will never break due to internal stresses, but it will greatly minimize the odds.

This, by the way, will only fix beads that have no visible cracks. You’d actually have to completely melt and cool any glass with visible fractures to cure it, which would of course ruin whatever it is you were trying to fix. This also will not guarantee that new micro-fractures will not develop in the annealed beads. If you decide to fry my beads, they will indeed go the way of my poor, unfortunate fried marble bracelet from all those decades ago.