Boro annealing schedules

[garishglobes]

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.

[fionaess]

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 ..

[fionaess]

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...

[stuwaudby]

The Northstar manual contradicts its self between the annealing chart and instructions. I quote:

Anneal 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

[garishglobes]

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!!!  ) 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!  ) 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! 

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

[Steampunkglass]

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!!!! 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?!

[garishglobes]

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! 

[stuwaudby]

Gah - I cooked some Amber Purple last night at 620c for four hours and NOTHING happend. I'm gonna give up with it.

[Steampunkglass]

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.

[Hamilton Taylor]

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

[garishglobes]

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.