Batch Annealing

Simbasmom · #1 2010-09-21, 4:36pm

I searched a lot of the Boro annealing threads but couldn't find what I was looking for.
When you batch anneal do you bring the kiln up slowly? If so what temps and at what time intervals.
Thanks very much.
Colleen

Bakerman44 · #2 2010-09-21, 8:44pm

i think it depends on the size of the piece...i've been told not to worry with it for med sized pendants and smaller. I've also been told i can put cold pieces in to a hot kiln and shouldn't have a problem. of course, I'm no expert and every situation is unique. I have not had a piece crack from thermal shock yet on full ramp batch anneal. nothing i make is more than 3/4" to 1" thick. Just test some junk pieces...it's a small cost to know how your kiln and glass will act around each other...

Simbasmom · #3 2010-09-22, 12:58am

Thanks for the help. Junk pieces???? What are those. LOL. Only kidding of course, being new to Boro I do have a few of those.
Colleen

glassdog · #4 2010-09-22, 6:43am

When I go out to my studio, I turn my kiln on to full ramp. I want my oven to get to 950 degrees as fast as possible. Then as I make stuff I put them in my oven. Sometime I need a long holding device to get them in there without burning my hands. Then when Im finished working, I turn my oven off. It takes 6 to 8 hours for it to cool down enough to take the items out. But I usually leave them in till the next day so they are cool to the touch. Then start all over again.
It works for me.

Simbasmom · #5 2010-09-22, 6:59am

Thanks Glassdog
Colleen

ginkgoglass · #6 2010-09-22, 7:53am

So glassdog, you don't anneal at 1050?

glassdog · #7 2010-09-22, 8:54am

I set my oven at 950. It climbs to about 980 at times. but only for a short period. That is what I have done for years and have had no problem. 1050 seems to be a little too hot for me. I'm somewhat of a rebel when it comes to lampwork. I hate to follow rules..hehe.
Tell me I cant do it and I will prove you wrong. Or at least try...hehe

glassdog · #8 2010-09-22, 9:00am

With solid items 4" in diameter, I just leave them in the over longer. I make a dog whose body is 4" at the chest and I left it in the 950 for 24 hours. then turned the oven off.
items 1.5 inches and smaller just a couple of hours at 950 will do the job. Or at least it does for me.

ginkgoglass · #9 2010-09-22, 9:14am

I get the rebel part because I'm the same way.
It can't be done that way? Really? Let me try . . .
My first flameworking teacher told me to NEVER put a piece back in the flame after you've let it cool. I now know that is not exactly true depending on how you do it.

glassdog · #10 2010-09-22, 9:29am

I put peices back in the fire all the time. I specialize in dogs, and most people want me to do their dog. I will make one then send them photos. they will tell me what I need to change and then I go back into the fire to make the changes.
Usually when I do that I start at the beginning of the day when I first turn my oven on. I put the piece Im going to be working on in the oven first then turn it on. By the time my oven is up to 950, Im ready to start working on it again. When Im finished, its back into the oven again till the end of the day when i turn it off.
You can also repair items in this manner. Put the broken piece in the oven let it come up to 950 then you can work on it without any problems.
With items less than 1 inch thick, I will put right into a hot oven.

TheSilicaForge · #11 2010-09-22, 12:44pm

I think for the temp too it depends what you are doing. I could see sculpture starting to lose it's detail if it was left at 1050 for too long, and that would just be heart breaking.

Dragonharper · #12 2010-09-23, 2:05pm

I just checked my Contemporary Lampworking Vol 1 according to the charts in chapter 8 the Rate for fast heat, room temp to annealing temp, for a 1 inch thick piece of COE 33 is 26.88 Deg F/Minute or 1620 Deg F/hour. Depending on your kiln you could put the piece in and go full tilt to annealing temp. YMMV.

Simbasmom · #13 2010-09-23, 4:08pm

Thanks very much everyone.
Colleen

oldschooltofu · #14 2010-09-23, 5:23pm

i have put 6" long super fats (26-32mm diameter) of color into the kiln at 1050 without any checking. i put marbles or pendants in a hot kiln cold and have not had one problem. i think unless something is extremely stressed it should be fine

if you dont soak at 1050 you are not going to get a proper anneal. yes your pieces may survive, but if you want to get it annealed all the way to the center of your piece you need to soak at 1050 for 3min every millimeter thickness.

PittsGlass · #15 2010-09-23, 5:59pm

I agree with the more conservative thoughts of oldschooltofu. The garage temp can be low to preserve striking colors, but it still needs to get up to the 1050 mark to properly strengthen your piece.

The blanket schedule we use is:

1075 for 60min
over the next 10 min drop to 1015 and hold for 30
over the next 10 min drop to 950 and hold for 30
then turn off.

It is a tad overkill if your pieces are not large and thick, but you don't have to change the program all the time for varied sizes.

You boro anneal schedule will have a lot to do with the color palate you use. There are many cycle variations to preserve certain colors over others.

TheNovice · #16 2010-10-01, 10:42am

A friend who set up my kiln and has made glass professionally for a decade gave me two settings on my paragon bluebird xl:

Program #1 - Turn on and get to 1050 as fast as possible. (Takes about 45 minutes). Any piece I am working on that wasnt done goes in the kiln when its turned on. I dont put in cold pieces to the kiln at 1050, only when its room temp and I'm turning it on.

Program #2 - After work, this takes temperatures to 1100 and holds it for 30 minutes. Then drops to 1000 for 30 minutes, then turns off.

I make mostly pipes and bubblers of 4-5mm thickness and 4"-12" in size.