I thought it might be useful to do a quick thread on boro annealing schedules so that the info is in one place. I've copied bits from various other threads, so that we have one thread to look at rather than several.
I think there may well be as many boro schedules as there are boro workers - but I hope these will give a start to anyone wanting to have a try with the hard stuff.
Boro can (specially for small pieces) be garaged with soft glass, run through the soft glass annealing schedule and then batch annealed later - useful to know if you just want to play at the end of a session using soft glass.
http://mikeaurelius.wordpress.com/2007/12/26/annealing-cycles-for-torch-made-glass/ (http://mikeaurelius.wordpress.com/2007/12/26/annealing-cycles-for-torch-made-glass/)
I used to use this schedule: (all in degrees C)
garage at 505, then ramp up to 565 at 80 degrees to anneal for an hour. I then ramp down at 90 to 510 to let the glass "rest" for 10 mins and then down to 370 and switch off
but now use one closer to Glenn's (Dendrobium) below, with a longer annealing time (my stuff has got larger) and a striking part at 590 added in. I have seen striking temps go up much higher than this - quite a bit over 600.
Hope he won't mind, but here's Glenn's schedule (also degrees C):
"I've seen various advice on garaging everything from 510 up to 540, but the important bit is ramp up to 567 for about 1hr, then a slow ramp down (about 46deg per hour) to about 525 for a short rest (10mins to 1hr depending how thick) then a slow ramp down to 370. Thicker bits will need a longer anneal, and if you've got ruby colours you will need to do an extra ramp up before the anneal to about 582 to strike the reds which tend to strike better in the kiln rather than in the flame"
Hi,
Thanks for the schedules. Can you please confirm is it degrees C or F
Good point! Have amended above!
I read somewhere there are as many boro annealing schedules as there are people working boro! :D
Just to add to the general confusion, I've started garaging even higher, at 560-565 deg c (1050 deg F) after reading Margret Meers book and other clever USA people who garage at the annealing temp to allow the stresses to come out, then they can take things back out of the kiln to work again with the advantage of it already being hot and partly annealed. I still ramp up the whole extra 2 degrees to 567 and leave kiln untouched and unopened at the end of day when I run the annealing program.
Although alot of the time lately I'm batch annealing cause it's just too hot! Most things seem fine, I think I've lost one marble to cracking in the past couple of weeks - and it was a lousy marble anyway! ;D
Great info for us softies who'd like to venture over to the dark side now and again... 8)
Glenn, does garaging at 560+ affect the colour at all, or do you notice no difference?
Quote from: garishglobes on June 24, 2010, 10:11:44 PM
Glenn, does garaging at 560+ affect the colour at all, or do you notice no difference?
I've not done it very much yet at the higher temperature, touch wood so far it's not seemed to have been a problem, but that is a good point as I know some of the colours like (I think) unobtainium have warnings about over garaging - I've had that cause cracking at lower temperatures.
The only colour that I've ever had a problem with is Red Elivis which tends to self strike, and I forget about the higher strike on the cycle and had that come out a rather grim shade of raw liver by over striking. Thats only really a problem though if I've used really thick layers of it.
Just to update this, I've now done a few sessions garaging at 565, and it seems fine
A batch annealing schedule would be nice - anyone got one?
I tend to batch anneal with this schedule too - I leave everything in the kiln, warm it up to garage temp then carry on working. When it's full or I've had enough for the day (usually the later!) I let it ramp to 567 and anneal.
Being an absolute dummy as far as my kiln is concerned - could you spell it out for me.. ie do I just tell it to go to to 505 from cold then increase by ? minutes to ? temp - hold it for ? and then decrease by ? degrees... Im confused now..... HEEEEEEEEEEEEEEEEEEEEEELP
Fiona, I now do this:
Ramp up to 565C at 700 degrees (ie full-ish), hold for however long to garage, then ramp up to 590C at 80 degrees and hold for 20 mins. Down to 565C at 80 degrees to anneal for 2 hours. I then ramp down at 90 degrees to 510C, hold to let the glass "rest" for 10 mins and then go down to 370C at 90 degrees and switch off
Thanks Emma - I'll see if I can 'program' that in... awwww shit now I have to remember how to do that :):) :)
Is this right?
Seg Rate Temp Hold
1 700 565C ---
2 80 590 20 mins
3 80 565 2 hrs
4 90 510 10 mins
5 90 370 ---
Anyone???
Sorry, missed that!
yes, it looks right for what I use (bearing in mind that if two of us use the same annealing schedule, it is unusual!) - I put the first hold at a good number of hours and then skip to the next stage when I'm done for the day.
Thank you.... well, its programmed, and my 'beads' (snigger) are in and it seems to be doing its stuff - well its getting hot, but I will keep an eye on it just to make sure it understood my instructions - and if it hasn't Im just going to switch it off .. ;D ;D ;D ;D ;D ;D ;D
Its now about 3/4 of the way through - has hit its appropriate temps/holds/times and on peering through the little window I can see whole beads - not a pile of melted glass - so hey, I might have done it... ;D
The Northstar manual contradicts its self between the annealing chart and instructions. I quote:
QuoteAnneal Time: 1 hour for every 0.25 inches of piece thickness
Soak Time @ A/T – 125 deg: 50% of the Anneal Time for pieces 0.25 inches thick or less.
100% of the anneal time for pieces greater the 0.25 inches thick
Soak Time @ A/T – 200 deg: 25% of the Anneal Time
Soak Time @ A/T – 350 deg: 25% of the Anneal Time
Soak Time @ A/T – 550 deg: 25% of the Anneal Time
All temperatures are in degrees F and for 33 expansion borosilicate glass.
So a 1 inch bead need to sit at 565 DegC for four hours. If you then follow the suggested ramp rate you need to drop to 260 over 3 hours which is 87 DegC per hour.
As for the ramp up speed, boro happily raises to over 1000 DegC in seconds when you melt a rod, use the maximum ramp rate of your kiln to save time and electricity.
Your program should therefore look like (in Deg C):
Ramp Rate - Target Temperature - Hold Time
Max - 565 - 4:00
87 - 260 - 0
Off
The softening point is 820 DegC so there is plenty of leeway for ramping up hotter for more strike.
http://www.northstarglass.com/UsersManual.pdf (http://www.northstarglass.com/UsersManual.pdf)
I read on another forum a couple of days ago that taking the kiln up to 620C and leaving it for 4 hours (yes, 4!!! :o ) had helped someone strike those purples.
I can't cope with the concept of my glass sitting at 620C for 4 hours yet (having come from soft glass, it was a big leap of faith to have it at 605) but I did decide to do a test run with various not-very-wonderful bits and bobs I had lying around here yesterday. The result for the schedule below was definitely interesting, with a lot of extra purple but little effect on the greens and blues that I put in.
I'm still not ready to use this as a general schedule, partly because I think there could be a risk of over-striking in the kiln (probably me being cautious), but I will definitely be putting anything a bit disappointing (ok, maybe I will use it a lot, then! :D) through an additional schedule just to see what happens. I'll probably take the time at 620 up to an hour, too - I'm brave, me! ;D ;D
Ramp 700 to 620C
Hold 30mins
Ramp 80 to 565C
Hold 2 hours
Ramp 80 to 525
Hold 20 mins
Ramp 80 to 370
00000000
I've stopped putting it up to 605 now, I was over striking the reds I now realise :-[ :-[ :-[ I was going that high to try to get the purples to take more colour, but I certainly wouldn't do 620 at 4 hours either!!!! :o :o I'm going up to about 582/583 for 15-25 mins and that seems to do the trick.
I'm getting better purples these days (touch wood!) and I think thats down to having a hotter torch getting rid of more of the initial fume, as well as being a little more aggressive when I strike them. I guess if the only colour you had in the kiln it might be worth it, but I'd wonder what it would do to the other colours, especially the 'don't deeply encase' sparlkly colours. If I understand the chemistry right (please feel free to correct me as I'm doing this from my hazy memory) in extended heating the metals (Chromium???) start reacting with the nearby glass changing the COE, so there becomes a localised area of 50-55coe glass in the middle of the 33, which causes cracking.
I fink thats wot I red once?!
Yup, I think I read that too. The chromium (chrome??) reacts with anything approaching an even vaguely reducing atmosphere and forms a micro-layer. Happy times!
I think I'd run this as a separate schedule if I had enough amber/purples that hadn't really struck as much as I'd like - it didn't seem to affect the other colours, but like you, I'd be too cautious to try and would worry about over-striking some things. Still, 4 hours! :o :o ;D ;D
Gah - I cooked some Amber Purple last night at 620c for four hours and NOTHING happend. I'm gonna give up with it.
Quote from: stuwaudby on April 04, 2011, 05:12:14 PM
Gah - I cooked some Amber Purple last night at 620c for four hours and NOTHING happend. I'm gonna give up with it.
:( :( :(
Have you tried Glass Alchemy's Triple purple or Northstars Silver creek instead? They are more concentrated so you might have better luck with them - however all of them need tp be got really, really, hot when initially you melt them else they just won't strike to purples.
Hi All,
This may have been mentioned here before, and I haven't read the full thread, but has cycling the annealing schedule been discussed? Leaving stuff in through several ramp up/downs certainly strikes silver and gold fume progressively, I suspect it may help with recalcitrant A/P colours. (eg when Emma restruck hers, it was effectively going through a second ramping process.)
Sean
That is a very good point and well worth a try. I have occasionally chucked a piece back in the kiln if I didn't think the colours were strong enough first time round. There's no harm in anything just sitting at the back of a kiln for an extra session.