A bit of reassurance please!

[ShinySnail]

I'm running my first ever batch anneal in my new sc2, and programmed it to heat up at 150 degrees an hour - but an hour into it and the temp is almost 200 degrees... should I be worried?

I fired it up earlier to burn off any factory residue etc and set it to reach 520 degrees, but when it got there it beeped and continued to rise so I panicked and turned it off myself - afterwards i thought that maybe i had chickened out too early and should have given it a chance to settle but now i'm not so sure! (It got up to about 160 before i turned it off)

Any advice would be much appreciated please, my only experience with kilns has been garaging at the odd lesson I have taken

Many thanks,
Anna

[mariag]

Hi Anna, I use the schedule in the following thread
http://www.frit-happens.co.uk/forum/index.php?topic=859.0

Think I used this to run the kiln empty first time too.
Have to say the schedule's worked perfectly every time.

[Zeldazog]

I'm running my first ever batch anneal in my new sc2, and programmed it to heat up at 150 degrees an hour - but an hour into it and the temp is almost 200 degrees... should I be worried?

Anna, depending on what temperature it was at before you set it to climb, it could easily be getting up to 200 degrees within an hour -

If it was already at say 38 deg C, add 150 degrees (per hour) and one hour later it will be at 188... 150 rate of climb + 38 it was already at.

When  you were doing your first firing to burn off any factory residue, what rate of climb were you using then?

You kind of have to imagine that a kiln, heating up is like a train or car - the faster it goes, the longer it takes to stop.  Obviously the thermocouple only knows it's reached it's target temperature when it gets there - it can't think beforehand to slow down or stop the heat - so, the elements will still be on, possibly full, when it reaches target temperature - THEN it switches off... but those elements are still hot (think of anything like an iron) - so still giving off heat - and your kiln is insulated - so it will continue to climb for a little while, until the "Brakes are on".

If it's going drastically over temperature, or you hadn't programmed a fast rate of climb, then you need to get it checked out - isn't the SC2 one of those where the thermocouple can come unseated?  I don't have one, so I don't know.

[Blue Box Studio]

I ran mine with it's first batch anneal topday using the schedule in the other post.  Mine was past 149 by the end of an hour but nothing seemed to have gone ping or bang so I left it.  Everything else seemed to go according to plan and it's coolling down on it's own now.  Fingers crossed.  The overall temperature only went a few deegrees over so I thought that OK. 

Have you checked the thermocouple thingy is inserted correctly?  It tells you in the manual how far in it should be.

Mine took 7.5 hours in total (+ cooling down time after I switched it off) is that about right?  Anyone know what it costs per firing (using the batch anneal schedule in the other post)?

[ShinySnail]

Ahhh thanks everyone - in the end everything was ok! I had used a similar schedule but it was the starting temp of the kiln I didn't take into account which is why I was worried when it exceeded the 150 degrees!

I only fired it up to 520 then let it cool at first which I now realise was a bit of an error as I spent the evening breathing in alll the crap it was still kicking out as I was frigntened to leave my first batch anneal unattended!

It all worked out well in the end though and I'm really confident about using it again.

One thing I was suprised at, there were a few beads that had noticable cracks that I popped in and they didn't actually break - You can still see cracks on the surface.
Are these still to be considered 'bad' or could the cracks have fused together?
I was under the impression that any weak beads wouldn't survive the annealing process at all?

[Mary]

Sorry, but the cracked beads are still cracked, they won't have "healed". Annealing doesn't get hot enough to soften the glass. Annealing does tend to show up cracks or weakness, but they don't always fall apart.

[ShinySnail]

OK thanks i'll bear that in mind, I saw one of those polarising lenses for sale recently - I might invest until I get a bit more confident!