HELP... What have I done wrong

Started by Essex Girl, April 17, 2013, 09:08:34 AM

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Essex Girl

I am hoping one of you kind people can tell what I have done wrong.

I got my first kiln (and SC2) last week and read everything on this forum about annealing.  As recommended I did a quick test firing then did a batch anneal with a few beads on the floor of the kiln and everything seemed OK.

Yesterday I got out my backlog of (mostly rubbish) beads and decided to use the 'pile them in a pyrex dish' method of annealing.  The result was a minor disaster, the beads came out stuck together in clumps and the dish has chips missing from the inside (there was also a small pile of frit in the bottom!).  The beads have all pulled apart but have small digs or bits of other beads sticking to them.  I am only too happy that I didn't put any of my 'best' beads in!

I used this schedule
Ramp1 149c, temp1 520c, hold1 60mins
Ramp2 80c, temp2 371c, hold2 0mins
Ramp3 0

Thanks for any Help

Karen
Karen
x

helbels

Your schedule looks o, but if the beads have melted and stuck together then it could be that your kiln is actually firing hotter than it's saying on the controller (this can be a common issue with kilns).  Where is your thermocouple located?  Is it sticking out far enough into the kiln (sometimes they get pushed back and this affects the reading).

I would have another try with some other beads with a top temp of 490 and see how you get on (that's still hot enough to anneal) - if that works ok then work with that.

Not sure why your dish has chips missing - the only thing I can think is that maybe it wasn't proper Pyrex, but some kind of cheap imitation of it?

julieHB

As well as what Helen is suggesting, check if your kiln overshoots the programmed annealing temperature - it can go quite a bit higher than the programmed temperature before it calms down. Normally this happens if you fire at full speed, and it shouldn't do with the rate you have programmed. However, it did happen to a friend of mine who had a new kiln (also a sc2), and I wonder if some of them can have "sticky" relay or something like that when they are new. After a few firings it stopped misbehaving.

Failing all, give them a call  :)

Julie xx

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Steampunkglass

Quote from: helbels on April 17, 2013, 09:17:44 AM
Not sure why your dish has chips missing - the only thing I can think is that maybe it wasn't proper Pyrex, but some kind of cheap imitation of it?
Some Pyrex dishes aren't made of 'Pyrex' anymore, instead they are now other toughened glass instead of the orginal borosilicate formula  :-\ I can't find it again, but there was a link on their USA website that explained how they had changed. I'm guessing there might have been some small knocks or stresses in the glass and at the higher than domestic oven temperatures caused them to break and chip off? Thats my best guess, so I might be wrong.

Essex Girl

Thank you Helen, Julie and Glenn

I will check if the kiln overshoots and change the temp to 490c (I didn't know you could go this low :))
The thermocouple seems to be in the right place and doesn't move.
My dish says it is Pyrex but maybe not made of 'Pyrex'.  I think I will use the 'kebab' method in future (less chance of beads sticking together even if they get softer than they should), I just need to get myself some steel mesh and cut down some old mandrels.

I was hoping to have a go at anneal-as-you-go (garaging?) today but I think I will make sure I get the batch anneal right first.

Thanks again
Karen
Karen
x

Blue Box Studio

I use a Pyrex dish, but it is circa 1950s :o and not had a problem in my SC2.  Having said that, the first time I fired it it overshot the temperature by miles (but not enough to melt anything) and I was told it was because I was ramping up by 'full', so set it to 'full' then press the down arrive once to get to the degree below full (can't remember how much that is right now) and not had a problem since.  I use the programme that's in a sticky thread on here somewhere. 
Sue
Website ~ Etsy ~ Blog ~ Flickr

flame n fuse

Hi

my sc2 programmes are
A. for batch annealing
260C per hour to 482C
hold for 30 min
83C per hour to 371C
Off

B. for annealing while you work
FULL to 482
hold for 5 hours
222C per hour to 371C
OFF

we have an SC2 and a larger kiln and find that both run hot. I do bullseye fusing and find that if I work at the recommended temperature I get devitrification and snaggy sharp bits on the edges of pieces.


comparing these programmes, I don't know why I have a faster cooling on the 'anneal while I work' programme than on the 'batch anneal'. But both progs seem to work fine with my beads (nothing larger than 3 x 1 cm).
I rarely work for 5 hours, but can advance the programme to commence the cool down.

hope this helps
Julia

Zeldazog

Quote from: Steampunkglass on April 17, 2013, 09:44:06 AM
Quote from: helbels on April 17, 2013, 09:17:44 AM
Not sure why your dish has chips missing - the only thing I can think is that maybe it wasn't proper Pyrex, but some kind of cheap imitation of it?
Some Pyrex dishes aren't made of 'Pyrex' anymore, instead they are now other toughened glass instead of the orginal borosilicate formula  :-\ I can't find it again, but there was a link on their USA website that explained how they had changed. I'm guessing there might have been some small knocks or stresses in the glass and at the higher than domestic oven temperatures caused them to break and chip off? Thats my best guess, so I might be wrong.

http://www.pyrexware.com/index.asp?pageId=30

Zeldazog

American Pyrex has been toughened soda-lime since the 1940s - I think the European Pyrex is still boro... I think. 

Essex Girl

Thanks for your programs Julia,  its looks as if they will also be a lot faster than my current program, being impatient this will be a good thing :)

And thanks to Sue, I will  bear this in mind when I program anneal-as-you-go.

Karen
Karen
x

Steampunkglass

Quote from: Zeldazog on April 17, 2013, 04:21:34 PM
Quote from: Steampunkglass on April 17, 2013, 09:44:06 AM
Quote from: helbels on April 17, 2013, 09:17:44 AM
Not sure why your dish has chips missing - the only thing I can think is that maybe it wasn't proper Pyrex, but some kind of cheap imitation of it?
Some Pyrex dishes aren't made of 'Pyrex' anymore, instead they are now other toughened glass instead of the orginal borosilicate formula  :-\ I can't find it again, but there was a link on their USA website that explained how they had changed. I'm guessing there might have been some small knocks or stresses in the glass and at the higher than domestic oven temperatures caused them to break and chip off? Thats my best guess, so I might be wrong.

http://www.pyrexware.com/index.asp?pageId=30


ah, that's what I thinking of - soda lime or borosilicate, I don't mind as long as it contains a nice home-baked fruit pie  :P