SC2 Kiln Issues

[Ciel]

I have an SC2 with a bead door and currently garage my beads at 512 degrees centigrade and anneal at 516 for 1 hour before allowing the heat to be ramped down gradually - I use COE 104 glass (CIM, Vetrofond, DH & Effetre mainly). 

However, I'm finding that about a third of my beads have small marks on them where they come out, or the large beads crack down the mandrel.  I work in the garage with a little heater on so it's a little bit cool working in there, but not uncomfortable.  I wait until the glow has gone from the beads and then wait some more before placing them in the SC2 through the bead door.

It's just soooo frustrating when I end up chucking out so many of them 

Am I putting the beads in too hot, is my program reasonable, or is there something else going on that I'm not sure about - any suggestions are really welcome!

[Dragonfire Glass]

I'd say too cool rather than too hot. Waiting til the glow has gone is plenty 

[sublimekate]

lets start with the marks, sounds like kiss marks to me, where the beads have got tacky in the kiln and tacked together during the holding segment, they have then separated again during the ramp down, hence the marks. This would suggest that your holding too hot and your SC2 controller temp display is not right, which isn't unusual for an SC2, and other kilns. I used to set my SC2 to garage at 500 and hold at 510 for an hour, then ramp down to 360 from there, I tested numerous beads with polorising filters on this setting and they were all annealed perfectly. I did this because holding at 520 I had exactly the same problem as you with the marks.

The cracks straight down the mandrels is an annealing issue, which could be that you're not holding for long enough or ramping down too fast or as already mentioned letting the beads cool too much before you put them in the kiln, I put them in glowing when garaging.

What rate are you ramping down at?

Also are you pushing the SC2 Bead Door closed as much as you can before annealing, if not beads near the door may not anneal properly and will crack?

Kate x

**Modified to say**

When you say larger beads how large are we talking, a 1 hour hold is only really good for beads up to a certain size, I said I annealed for 1hr but that was only for beads up to around 15/16mm, if I was annealing a large focal bead I would normally adjust this to 1.5hrs just to be safe, remember you can't 'over' anneal a bead 

[sublimekate]

I have lifted this from another thread for you, it was posted by redhotsal a few years ago, if you look through old posts in newbie questions you'll find loads about annealing problems 

In reply to questions as to how the polarising thing works I thought I'd put this together for people who are not sure about annealling.

You need to get a pair of polarising filters. You can use a pair of polarising sunglasses and break them up, or the fancy filters you can get for cameras (though these can be a bit expensive) or you can use that amzing research facilty - Tinternet - to source your own, which is what I did. I thought I'd get quite a few at the same time I got mine so that I could let other lampworkers have their own. So, if you want a pair, email me and I will sell you a pair for £6 inc P+P.

In answer to a previous question - yes - I do have a website, just click on the pink beads banner at the base of this thread. And yes, I was a scientist in a previous career. Optical Physicist in fact.

They only work with transparent beads so what I normally do is make a plain clear spacer type bead every now and then and pop it in with the batch of beads that I'm annealling. This will give some indication of whether the batch has been successfully annealled or not. It's a good idea to make this spacer quite large as larger beads require more soak time at the annealling temperature. Basically if your largest bead is properly annealed then you can be sure that all your smaller ones will be fine aswell.

When you look at the bead try to sandwich the bead between the two filters. Ideally you want a source of diffuse light behind you. I'm lucky enough to have a little torch type thing which I sit the filters on, but you can hold them up to a window and use daylight. A lightbox or the "white" sky that we seem to get often in the UK - bright with a continuous cloud - is an excellent light.

Rotate the top filter with respect to the bottom one and you'll see that the transmitted light starts to go from  light grey to black and as you carry on rotating it beomes light grey again. If you look at the unannealled bead you'll see that it has a series of stripes radiating out from the bead hole - often in the shape of a Maltese cross. These will rotate as you rotate the filter. These are the stress lines. The more visible they are the more stress you have in the bead. A properly annealled bead will not display these lines at all it will just go from transparent to black as you rotate the filter.]

It really is a startlingly good representation of the stress lines that are in the bead. Polarisers are routinuely used for stress analysis of various objects. I have to say it gives me great peace of mind to know that there is a tangible aspect to annealling. It takes the guess work right out of it and is an excellent and vivid tool to demonstrate to your customers (if they're at all interested!) - especially if you compare your lovely annealled bead to some imported unannealed rubbish that they're raving about.

Just another way to show your customers that properly annealled beads are worth the extra pennies!

I took this advise from Sal and tested transparent beads that I'd annealed on different scedules on my SC" until I found the one that worked and didn't make the beads stick together, because all kilns can fire at different temps you really need to test your own to be sure.

Hope that helps. Kate 

[Ciel]

Thanks thats given me something to have a fiddle with.  The largest bead I made was a lentil which cracked: 45mm x 45mm x 15mm, but that was unusual, they are usually 25x25x8mm lentils.  I'll try 500 for garaging then 510 for annealing.  The program I use is as follows:

Step 1: Ramp speed: Full, Target 490, Hold 0:00
Step 2: Ramp speed: 50, Target 512, Hold 10:00 (I make it skip to the nex step once I've finished making beads)
Step 3: Ramp speed: 50, Target 516, Hold 1:00 (annealing bit)
Step 4: Ramp speed: 50, Target 454, Hold 0:10
Off

I've got a polarising filter for camera, what would I be looking for to check it's been annealed properly?

[Ciel]

Forget the polarising bit , this answers it!

[sublimekate]

Thanks thats given me something to have a fiddle with.  The largest bead I made was a lentil which cracked: 45mm x 45mm x 15mm, but that was unusual, they are usually 25x25x8mm lentils.  I'll try 500 for garaging then 510 for annealing.  The program I use is as follows:

Step 1: Ramp speed: Full, Target 490, Hold 0:00
Step 2: Ramp speed: 50, Target 512, Hold 10:00 (I make it skip to the nex step once I've finished making beads)
Step 3: Ramp speed: 50, Target 516, Hold 1:00 (annealing bit)
Step 4: Ramp speed: 50, Target 454, Hold 0:10
Off

I've got a polarising filter for camera, what would I be looking for to check it's been annealed properly?

Mmm I think 454 is a little high to stop the annealing, your ramp down is actually the most crucial part of the 'annealing bit'  I would recommend  370 or even 360 to be safe because of course we don't know exactly what temp you kiln is firing at, it could be 10c or more either way from what is actually displayed, it sounds like it's firing hotter, which could mean that your ending your annealing at 464 or close to 474c which I'm sure is not cool enough and with the bead door adjar the temp is certainly not the same throught the kiln that's a cert!

This is what I used to garage:

RAMP 1  -FULL
TEMP 1  -500 
(Yes it overshot a bit ramping at full but not enought to fail the programm, your SC2 will allow you to overshoot by 23c before spitting its dummy out  lower the ramp a bit if it does overshoot too much)
HOLD 1 - 13hrs
RAMP 2 - 100
TEMP 2 - 510
HOLD 2 - 1hr
RAMP 3 - 78
TEMP 3 - 370
HOLD 3 - 00.00

This is the one that finally worked for me. K xx

[Ciel]

I've just made 6 beads - all 25x25 lentils including a large clear one so I can see what it's doing through cross polarisation and waited just until I couldn't see the glow.  I'll also alter my program for next time to see what happens as well as making another clear bead to re-check.  It does sound like the kiln might be too hot though and I was putting my lentils in too cold.

I'll see what the kiln has to offer tomorrow.

Thanks for your help

[Ciel]

Well all the lentils came out of the kiln with no cracks 
Just need to test the clear bead to make sure they're annealed OK.

Thanks for all your help!

[sublimekate]

Cool 

Glad things are going better, any kiss marks?

[Ciel]

Not tested that yet, but ordered some polarising sheets in the meantime.  Will try that tomorrow night when I have some spare time

[firedinglass]

 I have an SC2 and garage at 530 - 535 C  any lower and i have problems.  I just assume my temp is not accurate and go with the flow of my own kiln!   I have found over time that all kilns vary and you just have to find what suits you using others as a guide only.

[Ciel]

It looks that way.  I made a few beads last night and placed them in the kiln as soon as the glow had gone.  However, I ended up with hugh kiss marks and some stuck together, which wasn't ideal, but when I went back to waiting a bit longer, I had some crack and slight kiss marks.  It's so frustrating!  I'm just going to have to fiddle until I get it right.

The only other option I have is to batch anneal if I can't work this out, but I prefer garaging

[Dragonfire Glass]

You can try keeping the beads separate more - use a rack or something like that.
The other thing you could try is to hold it inside the body of the kiln a bit before putting it down.
Rubino is a b***r for sticking 

[soulsilver]

I had a similar problem with my kiln and I used a multimetre with a temp sensor and tested the kiln every half and hour or so, then looked at the results over the course of a cycle and it turned out that my kiln was running 34degrees higher than it should have been, I adjusted the temperatures according to that and its now working great!