If your name is Wallace you might mean this as a compliment, and Gromit might be glowing with pride and joy. Unfortunately this post is not so happy, but hopefully might help explain some of the reasons that glass beads can crack.
Here is the reason I am writing this post -
'Tis a sad sight indeed! This picture explains why glass beads should be
annealed!! I did not drop it, and didn't hear it crack when I put it down so can only assume it cracked all by itself.
I'll explain a little -
When I make my beads I save them up and then '
batch anneal' them. This means that they all go into a kiln together for a nice hot soak. Much like a hot bath can relieve the stress of the day for us, a soak in a kiln relieves stresses that have built up in the glass during the beadmaking process. - Well, it's not quite the same process, but it seemed like a good analogy!
This was one of my favourite beads that I was waiting to have annealed - I'd been wearing it because I liked it so much and you can imagine what a shock it was to find it in two pieces. The stresses in the glass were just too much causing it to split in two.
I decided to write a post for new beadmakers and bead purchasers to help explain why annealing is important and also some other things that may cause a bead to crack. The above picture explains the annealing part of the post and the following pictures will explain a few other things that can happen.
When a bead is made the glass is subjected to extreme heat, depending on the design of the bead the heat may not be distributed evenly through the glass. As the bead cools and stress is introduced '
thermal cracking' can occur -
At least this is what I believe has happened here. The bead has cracked in half along the mandrel hole in a nice clean line. If this happens the bead might fall apart before it even comes off the mandrel, or you might notice a crack that causes the bead to fall apart soon afterwards. I have noticed that keeping a bead in the cooler part of the flame longer once it is made reduces how often this happens. '
Garaging' or putting your beads straight into the kiln may also prevent this.
'
Incompatibility Cracks' are quite different. I had to experiment here as I'd never actually seen one of these.
You can see that the two beads have broken apart into small and larger pieces that have no uniformity to them. These beads were made by mixing two glasses of differen't COE's together - the glass is incompatible.
I've read that there is a 5% rule when mixing incompatible glasses, that you can put a higher COE in small quantities over a lower COE but not vice versa, and also that even glasses of the same COE can be incompatible. If you want to know more about COE's and compatibility
click here. Generally speaking if you use one type of glass in a bead you should not have problems.
On to perhaps the saddest of the cracks - this one I'm calling a '
Stupidity Crack'
It looks much like a thermal crack but has a different cause. This crack was caused by cleaning the bead too roughly with a diamond bead reamer. I've done it more than once, so I am convinced of this. If you are using a diamond reamer to clean your beads -
be gentle!! I heard a 'ping' as I rammed the reamer far too roughly (say that six times fast!), and the bead fell apart in my hand.
So, there are my sad pictures for the day.
If you buy beads. . .If you are someone who buys beads I hope this will explain why some glass beads may seem more expensive than others. Glass bead artists who take pride in their work know the importance of annealing and will usually mention it in their information. They are also aware of the different types of glass and which can be used together. The old saying rings true -
you get what you pay for. Many imported beads are made from inferior glass and have not been properly annealed, they are likely to crack and have very short lifespans.
I will not sell beads that haven't been properly annealed. If you see new beads or beads listed as 'coming soon' in my blog and site you can rest assured that before they go up for sale they will be annealed.
If you make beads. . .I hope the pictures help to show some of the differences and similarities in cracked beads. I am not an expert, and only sharing what I have learned so far. I am happy to receive comments, there is so much to learn!
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