Hi,
Does anybody know if the polarising lenses you use to check if your beads are annealed properly (mentioned in the wiki) are the same as the polarising filters for cameras?
I can't seem to find much else on ebay...
Thanks,
Anna
I have some polarising lenses from Sam somewhere. If you can wait a while until the unpacking is done, I'll get them sent to you Anna (spare ones see!). You'll have to remind me though, you know how dippy I am. ;)
If you've got a pair of 3D specs from a recent film you can use those.
Ohhh thanks both of you, I think I may have half inched a pair from Alice in Wonderland ya know ;)
Cheers Sue ;D I'll check out the situation with those glasses and let you know if I can't find them but I'm pretty sure I know where they are....
Ta v much!
I'm not totally sure - but they should be. A way to check:
Take a polarising lens from the camera and hold it up to a flat computer screen (a modern LCD one - not an old fashioned monitor). Make sure the screen is switched on and try and find a bland white desktop. As I write this reply the white box for the reply is ideal....Alternatively use the document page for a word document. Rotate the filter (holding it parallel to the screen like it was a magnifying glass) and you should see the filter cycling through clear to black. If that happens then you can use the filter.
Using the set up as described above you can "sandwich" your bead in between the filter and the LCD Screen. Repeat the rotating motion and as long as the bead is a transparent one you should be able to see the stress lines as black shadows. A properly annealed bead will be either totally clear or very nearly black all through. An unannealed bead will have an interesting "Maltese Cross" of shadows. The more stressy the more shadows you will see.
I have some polarising lenses somewhere. They are £8 for the pair inc P+P. Let me know if you can't find anything and I'll see if I have any left.
Yup, polarizing filters for the camera work great. I took this photo by putting a polarizing filter on my camera and holding up the bead in front of my computer screen (just turn the filter until most of the light goes away) ;D (The bead was cooled in vermiculite.)
(http://rangifer.se/exp_img/not_annealed.jpg)
Also "Polaroid" sunglasses :)
Thanks very much for all the info, I will investigate ;D
I have been making some beads recently that I'm a little suspicious of and wanted a bit of reassurance that they would last!
They are made up of blobs of glass with lots of holes in between so may be a little iffy...
Well, in fact, the thinner the glass the less likely there is to be stress. That's a bit general but, on the whole where you have a large bulk of glass then you get a big differential between the outer temperature on the surface of the glass and the core temperature. It's this differential that leads to stress - which then leads to cracking.
A large paperweight, for example, has such a huge temperature differential that some of them have to be annealed for DAYS rather than hours. On the other hand, you can pull a stringer and use it immediately without annealing because it's so thin that the inner and outer temperatures are much the same.
It's somewhat counter intuitive but if you have made a bead with lots of air gaps then in fact it's probably much less inclined to be stressy than a big solid lump of glass. :)
Ahhh that explains why these beads seemed virtually indestructable when making them!
I thought i'd suddenly got good lol
Thanks Sal
Aha! Knew I had a polarising lens somewhere! I got one years ago for my old Canon A1 film camera. Just tried it out and wow, isn't that clever! :o
Plus, it looks like if I get a stepping ring I can use it on my digital camera for photographing beads...should be very handy, as it cuts out reflections. Loving this thread ;D