Sunday, 18 July 2010

Bead Annealing

There are two approaches to annealing beads.

One is to keep them warm as you make them and when the session is finished, anneal all the beads sitting in the kiln. Assuming you are using soda lime glasses rather than borosilicate, you need to have the kiln idling at around 500C. When you have evened the heat throughout the bead, you place it in the kiln. Gloves and other heat protection attire will be needed when you open the door/lid to put the bead on the mandrel into it.

When you have finished the bead making session, you then take the temperature up to about 520C – 540C and soak there for about half an hour – both depend on the type of glass and the thickness and shape. The object is to take the glass up to a temperature where the annealing process can work, but without being so high in temperature that the bead takes up marks from the kiln shelf. More information on the soak and annealing of various shapes, sizes and types are given in later tips.

The second method applies if you have cooled the beads in vermiculite, blanket or other means to cool them slowly and you now have a group of cold beads that you wish to ensure are correctly annealed. You need to start the kiln from cold. Place the beads in the kiln and begin the firing. You need to take the beads up slowly – not more than 300C/hr - to between 520C and 540C, and soak there for about an hour. More information is given in further tips.

In both the cases described you now have the beads with the temperature equalised throughout the bead, and the annealing can begin. The annealing is the controlled cooling below the annealing soak. It is generally safe to take the temperature down at about 80C/hr to 360C. After this point you can speed up the cool down to something like 200C/hr, or if you kiln cools slowly enough, just turn it off and wait for the temperature to come down toward room temperature. This again depends on the type of glass, its size and shape.

Variations according to glass type used, sizes and shapes follow in further tips.
Annealing of Borosilicate Beads
Annealing of Bullseye Beads
Annealing Effetre Beads
Annealing Spectrum 96 Beads
Effect of Shape
Effect of Size
Effect of Variations in Sizes