What's the lowest temperature you can anneal at?

[Redhotsal]

If I put a glass rod in my Maxine at "520C" I know it would warp slightly. This tells me that the kiln is not actually at 520 inside. No problem, I just turn the kiln down and anneal at what the kiln says is 490 which seems to work fine.

I had to recently anneal Lucio's figures (with the the teeny tiny thin-as-gossamer stringer fingers and hands!!! ) recently. Both myself and Di (East) were absolutely bricking it before hand in case I slumped the figures(!!!!)  so as an experiment I made a "tree" of fine stringers coming out at all angles and absolutely hair fine. I had to use my pottery kiln as the Lucio figures were too big to go into the Maxine, I also tossed in a few transparent beads as well so that I could check if the glass was actually annealing.

I found that I could anneal at 480 without the glass slumping, even the "stringer tree" was still solid but also a check with the polariser revealed that the transparent beads were also annealed well at this temperature.

To be honest - unless you have a calibrated kiln you don't really know what temperature it actually is at inside the kiln - and in the case of a long boxy kiln like the Maxine - there's probably a range of temperatures anyway across the chamber. Yes, I agree cones will give you a good indication of temperature accuracy and you can get them from places like pottery craft http://www.potterycrafts.co.uk/Products/00100005, but as long as you can check the anneal with polarisers you probably don't need the cones. I would be inclined to experiment with lower temperatures (check the anneal with each run). Do use a range of colours though, as in my experience Effetre transparent green, for example, needs a slightly higher temperature than the clear. BTW - Effetre will anneal at a much lower temperature than say, Lauscha or P+T.

[Redhotsal]

But as Michael Cardew said "it doesn't matter how bad the kiln is as long as you are used to the bugger"

That's very true. I won't say my Maxine is bad (only in a "gangsta" way!  ). I love that kiln, but at the same time I couldn't honestly say it was temperature accurate either. But, yes, I'm used to it and I wouldn't change it for the world! 

[Fiona]

Thanks for the advice everyone I really appreciate it. I think for now I shall experiment with the temperature as it's only the rods I've had a problem with so I'll test lower temperatures with just them.

Where do you buy polarisers from and do they come with simple instructions?

[Redhotsal]

There's a thread on here about polarisers and how to use them.
You can get polarisers from MUTR : http://www.mindsetsonline.co.uk/index.php?cPath=418_2_446&osCsid=biou2g8j2d2tnvag995rkb6u22
They won't come with instructions as they can be used for many different things, but the FH thread should tell you all you need to know.
You can also use a pair of 3D specs from the cinema if you have them or polarising filters from a camera.
If using the specs you need to "pop out" the lenses and you'll also need a computer monitor (new style LCD panel, not an old monitor. In the monitor there will be a polarising lens so you only need one lens.

Here are a couple of links to using the filters (ignore my self righteous rant on it!  ):
http://www.frit-happens.co.uk/forum/index.php?topic=2057.0
http://www.frit-happens.co.uk/forum/index.php?topic=32530.0

[Fiona]

Thanks Sal.  I think I've got some specs somewhere so I'll have to try and find them.   

[Lilley]

Sounds like your kiln is running hot, but it may also the speed at which you are taking it up that might not be helping.  I used to batch anneal and took it up fairly quickly, I was using a hobby fuser kiln, the kiln only knows the temperature it is currently at so what I think was happening for me is that the kiln would get to 520C and cut off because it had reached the top temperature - BUT because it was still heating at what ever degrees/hour I had set it at just before reaching 520C it would over shoot, answer for me was to ensure that I slowed the ramp down for the bit near to 520 or set it to a slightly lower temperature so that it didn't over shoot.  Only discovered this when I ruined a whole batch because they slumped just enough to pick up a flat on the bottom of every bead - very cross making!  Now I anneal as I go along (I acquired a bead kiln), the cost of having the kiln on is very little for me, I was pleasantly suprised when I did the maths.  I made some icicles yesterday and simply put them on the bottom of the kiln and they were fine.  As a by the way some kilns have hotter areas and cooler areas so it is about knowing your particular kiln too.

[Fiona]

Thanks for the input Lilley.  Although my kiln more than likely does have hotter and cooler areas these were annealed across the whole width of the kiln and on 2 different height levels so I think it has gotten too hot generally rather than just in places.  The programme I used I think was from another thread on here so I'm not sure how quickly I should ramp it up.  I find all the science of annealing a bit confusing at the mo' but I suppose over time I'll understand it more.  The reason I batch annealed these was because the rod of the stirrer was cold with only the top where I made the design being hot so I assumed putting a cold rod of glass into a hot kiln wouldn't be a good idea.  When I get around to making the icicles the whole thing will be hot so I will probably put those into the kiln as I go along and hope they'll be ok.  A bit of trial and error is needed me thinks.