Relieving stresses by hand annealing?

[2cool2hear]

Relieving stresses in the glass can be performed by hand annealing, which is a process of using a torch flame of diminishing intensity and size over time, slowly and evenly allowing the glass to return to room temperature.

An alternative is to use a glass annealing furnace. The bell-type furnace shown here is programmable to allow pre-determined ramps up to the annealing temperature(s) and then back down to room temperature.

I was reading some stuff about relieving stresses in glass by annealing and came across this site (http://www.ilpi.com/glassblowing/glassstress.html) saying you can hand anneal as a first choice, and alternatively use glass annealing furnace. Thoughts?

[Mike_Aurelius]

Can you hold the piece in the flame for a couple of hours?

[Jimi The Don]

I don't see the fraise "first choice" anywhere on that page.

[Jimi The Don]

It specifically states that most glass workers will flame anneal and then anneal in an oven before delivering their apparatus. I flame anneal all types of shit, and as soon as I'm done I stick it in an oven and anneal it real proper like. I'd never deliver a finished product that hadn't been annealed in an oven.

[Papa Jim]

Annealing is not just getting glass hot for a long time. To fully anneal glass you must heat up the entire piece at the same time and hold that temp for about 30 min. then have it slowly cool down through the strain point. This is very important for heavy wall glass. Anytime you work glass you are putting strain/stress in that piece, the heaver the wall thickness the more stress you will have. Bench flame annealing is a must if you are not garaging a piece after working it. But it will not replace a proper annealing cycle.

[hashmasta-kut]

stress is removed in about 30 minutes is misleading i think. It is dependent on the thickness of the piece, and for example a 2 inch marble i think its something like 2 hours, or is it 4? not sure, i just know its a lot longer for a lot thicker.

An interesting thing about flame annealing i have found, is that when working with stuff like clear tubing for example, if you are one who diamond shears it, a very brief flame anneal after a flame polish will take enough stress out that you can reheat the tube the next time you need it much more quickly, with low risk of breakage. it just takes like 30 seconds, and it does make an appreciable difference, also for blowtubes that have been flared out thick and wide on the end and let cool.

[art vandelay]

i dont understand why alot of people try to dodge the kiln when they are first setting up. they are one of the cheaper pieces of equipment in the shop, and it would suck to try to work without one.

[hashmasta-kut]

first time i saw Hamm working, he didnt have his kiln on, i was like whats up with that; he said he didnt need it for all he was doing so far. learned a lot right there.

[art vandelay]

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[hashmasta-kut]

whatever bro, just pointing out than an expert glass worker knows when they needs to use a kiln or not, and paying attention to those kinds of things helps us newer melters. if i just said some guy did it, it wouldnt have much credibility.

[LooseSeal Baller]

i dont understand why alot of people try to dodge the kiln when they are first setting up. they are one of the cheaper pieces of equipment in the shop, and it would suck to try to work without one.

A kiln is the second most expensive thing i have...besides the torch. I'm not understanding what you mean.

[art vandelay]

A kiln is the second most expensive thing i have...besides the torch. I'm not understanding what you mean.

oh... what i mean is you can get them dirt cheap. yeah you can blow a huge wad on one too... but i barley blew my wad. a few dribbles at most. torch, ventilation, oxy tanks (depending on how many) are less readily available used and as a result more expensive

ive just seen a ton of people lately who are just getting into the craft and they try to avoid this step. and i can see why, things like flame annealing crockpots vermiculite and the article above lead you to believe you can achieve the same results without a kiln. but can you?

[n3rd]

any of you guys have a polariscope in your shop? you might find it very interesting, i know i do

[art vandelay]

i just wanna clarify i relieve a lot of stress by hand. if you dont tension can build and things can burst at inopportune times. my point is theres a time and a place for everything. so if you can tell that some tension is building grab that rod and work it out... you know? work that tention till the rod is good and floppy. then when it gets hard again... well i dont have to tell you guys what to do.

so take your rod and either work it out by hand or put it in a nice hot hole for a while.

[snoopdog6502]

Kilns are kind of funny to shop for. A decent desk top kiln is $500 -$900 but I can buy great big top loader for under $300 used that are not suited to lampworking.

I want a new desktop but will still buy a big used one someday for bigger stuff.

Right now I post heat in a bushy flame for a minute then bury my stuff in a bucket of perlite. It sucks ass not having a kiln.

[art vandelay]

i got my bench top kiln/controller with bead door for 300.

[the-thought-police]

I was in a shop today, where a guy had a piece on a lathe, just spinning away with 2 torches on it not nearly hot enough to melt it. That's exactly what I figured he was doing. His kiln was too small to handle such a big piece, so he seemed to be annealing it in the flame, by stepping it down very slowly, letting the lathe do all the work while he did other stuff by hand at a different station. I can imagine it's not at all uncommon a practice amongst lathe workers, but for smaller free hand stuff, especially the simpler stuff, just using vermiculite to slow cool it has always sufficed for me. Vermiculite doesn't anneal anything, but for simple stuff it allows it to cool without cracking until you can anneal it. If you don't have a lathe and stationary torches doing the flame annealing for you, it's going to be a bit of a waste of time holding something in the torch that long yourself.

[PyroChixRock]

stress is removed in about 30 minutes is misleading i think. It is dependent on the thickness of the piece, and for example a 2 inch marble i think its something like 2 hours, or is it 4? not sure, i just know its a lot longer for a lot thicker.

An interesting thing about flame annealing i have found, is that when working with stuff like clear tubing for example, if you are one who diamond shears it, a very brief flame anneal after a flame polish will take enough stress out that you can reheat the tube the next time you need it much more quickly, with low risk of breakage. it just takes like 30 seconds, and it does make an appreciable difference, also for blowtubes that have been flared out thick and wide on the end and let cool.

2 inch marble kiln cycle from contemporary lampworking:
Ramp up to 1058 at no faster than 17 degrees per minute.
If you are already at 1058...

Soak for 153 minutes
Ramp down to 900 over 45 minutes
Ramp down from 900 taking at least another 67 minutes.

[snoopdog6502]

2 inch marble kiln cycle from contemporary lampworking:
Ramp up to 1058 at no faster than 17 degrees per minute.
If you are already at 1058...

Soak for 153 minutes
Ramp down to 900 over 45 minutes
Ramp down from 900 taking at least another 67 minutes.

Wow,so I figured every time I turn on a kiln my power bill will jump a couple bucks.

$100 a month or so?

[PyroChixRock]

There is a formula for time per mm of thickness floating around here somewhere. 2 inch marbles are huge. I don't even make them that large very often and I make marbles 98% of the time.

So no. I doubt it. A regular annealing cycle for pipes and pendants and the like is much shorter.

Unless you are garaging all day while you work, just annealing glass doesn't cost much.

[the-thought-police]

Wow,so I figured every time I turn on a kiln my power bill will jump a couple bucks.

$100 a month or so?

Naw man, I use my kiln almost every day, all day some days, and there are months when my electric bill isn't even $100. During the winter, the gas drives it up to heat my house to over $100, but never during the summer. I've always felt any difference in electricity costs to run a kiln was infinitesimal. Then again I'm using a pretty standard sized paragon with the regular plug, nothing too big or anything.

[art vandelay]

You must spread some Reputation around before giving it to the-thought-police again.

[SkoGlass]

Naw man, I use my kiln almost every day, all day some days, and there are months when my electric bill isn't even $100. During the winter, the gas drives it up to heat my house to over $100, but never during the summer. I've always felt any difference in electricity costs to run a kiln was infinitesimal. Then again I'm using a pretty standard sized paragon with the regular plug, nothing too big or anything.

Electric and delivery must be cheap in your area.

[PyroChixRock]

The last time I calculated kiln cost was when I was in portland, so 2008ish. It was $89 a month to run an aim 9169gs full time, and I mean like insane glassblowing hours, 12+ hours a day average easy. I know that's not a very recent figure but it can give you something to go on.

[Greymatter Glass]

Can you hold the piece in the flame for a couple of hours?

Depends on the piece. Thin wall scientific glass that starts out being made properly can be annealed (if it even NEEDS it) in minutes.

Big heavy marbles could, in theory, take several days to anneal fully.

Annealing has a lot of variables, time is only one of them. I know you know that.

Point is, without more details it's impossible to say is a particular item can be flame annealed efficiently, but the answer is universally "yes".

You also have to figure cost of fuel/oxygen vs. electricity - electricity will almost always be cheaper.

[Greymatter Glass]

I was in a shop today, where a guy had a piece on a lathe, just spinning away with 2 torches on it not nearly hot enough to melt it. That's exactly what I figured he was doing.

Yep. I have annealing burners from a sci. shop I bought years ago. Big bushy natural gas / air burners that have a needle valve on them, meant to be held on a lab stand.... they're often enough to effectively anneal glass.


Vermiculite doesn't anneal anything, but for simple stuff it allows it to cool without cracking until you can anneal it.

You're right that vermiculite doesn't anneal glass. When done properly (i.e. the right glassware) the glass anneals itself, the vermiculite justinsulates it so it doesn't cool off too fast. For that matter, you could anneal something in air, or even water, with the right glass and right conditions....


_ALL_ annealing is, is the process of holding glass above it's strain point and below it's liquidous temperature for a period of time long enough to both equalize and relive the tension in the glass below a point considered to be acceptable - then cooling it slow enough so as to not reintroduce mechanical stress from the contraction of the glass it's all a function of heat, time, and glass properties associated with each. IF you have a piece of glass that's not overly stressed to start with (maybe a simple clear jar) and get it evenly hot above 1000ºF , and get it in vermiculite before it hits about 940ºf, and it's thin enough to be cooled rather quickly, then when you take it out you could, for all intent and purpose, call it annealed.

The same would not be true of a 2" marble, or something with color in it, or other factors....

Borosilicate glass is tough stuff, I read somewhere years ago it has a tensile strength of about 2000psi (not to be confused with psig, or gas pressures) - as long as you're well below that over the entire piece it shouldn't break on it's own. Flame annealing will get you down below that point usually... but you can always do more by holding it at the anealing point for a period and letting it equalize... high strain areas move into low strain areas, but there's still stress in the glass - you can't remove it all. ever. it's impossible, like a pure vacuum, absolute 0º, or walking across a room by going half the distance then half again over and over.


Now, all that said, for what MOST of us do with glass there is NO SUBSTITUTE for kiln annealing your finished work. Skipping out on a kiln is like buying a car and skipping the wheels. yeah, you can get in the driver seat and make cool revving sounds and turn the steering wheel, and honk the horn - but you're not going to go very far.

[snoopdog6502]

Naw man, I use my kiln almost every day, all day some days, and there are months when my electric bill isn't even $100. During the winter, the gas drives it up to heat my house to over $100, but never during the summer. I've always felt any difference in electricity costs to run a kiln was infinitesimal. Then again I'm using a pretty standard sized paragon with the regular plug, nothing too big or anything.

Yea, I want a kiln with a 120VAC plug but can wire a big one if needed later on.

Im not afraid of a power bill, its plenty high now, with the small stuff I will do and save up stuff and anneal in batches it wont be bad then.

I realy like the idea of garaging work so I can make several pieces then weld them all up nice and hot. Or just take a break and come back to hot and ready glass.

A kiln is my next investment for sure.

[PyroChixRock]

Yep. I have annealing burners from a sci. shop I bought years ago. Big bushy natural gas / air burners that have a needle valve on them, meant to be held on a lab stand.... they're often enough to effectively anneal glass.



You're right that vermiculite doesn't anneal glass. When done properly (i.e. the right glassware) the glass anneals itself, the vermiculite justinsulates it so it doesn't cool off too fast. For that matter, you could anneal something in air, or even water, with the right glass and right conditions....


_ALL_ annealing is, is the process of holding glass above it's strain point and below it's liquidous temperature for a period of time long enough to both equalize and relive the tension in the glass below a point considered to be acceptable - then cooling it slow enough so as to not reintroduce mechanical stress from the contraction of the glass it's all a function of heat, time, and glass properties associated with each. IF you have a piece of glass that's not overly stressed to start with (maybe a simple clear jar) and get it evenly hot above 1000ºF , and get it in vermiculite before it hits about 940ºf, and it's thin enough to be cooled rather quickly, then when you take it out you could, for all intent and purpose, call it annealed.

The same would not be true of a 2" marble, or something with color in it, or other factors....

Borosilicate glass is tough stuff, I read somewhere years ago it has a tensile strength of about 2000psi (not to be confused with psig, or gas pressures) - as long as you're well below that over the entire piece it shouldn't break on it's own. Flame annealing will get you down below that point usually... but you can always do more by holding it at the anealing point for a period and letting it equalize... high strain areas move into low strain areas, but there's still stress in the glass - you can't remove it all. ever. it's impossible, like a pure vacuum, absolute 0º, or walking across a room by going half the distance then half again over and over.


Now, all that said, for what MOST of us do with glass there is NO SUBSTITUTE for kiln annealing your finished work. Skipping out on a kiln is like buying a car and skipping the wheels. yeah, you can get in the driver seat and make cool revving sounds and turn the steering wheel, and honk the horn - but you're not going to go very far.

And this is why we call him the mad scientist. :D

[Kamil84]

Kinda agree^ If we're talking new equipment and for the most part still agree in regards to second hand equipment. But if your in the market you'll be shocked at the deals out there! (Is what I think V ment, correct me if I'm wrong) but most of us starting out don't really know prices what we want/need or where to get it well priced. But like I said new or old a little digging and you'll find gold (lol yeah 1st pun of the day)
As for "dodging" the kiln on setup I can only speak for myself... Money lol! Safety first you'll spend 500$ easy on vent and glasses and mayyyybe some nice fire blanket. But then you need a torch and regulators and some cool tools!? BAM you just spent another 700$ lol. And once you get this you of course need glass, another 100$
So to recap we just spent 1,300$ In one sitting assuming we got some good deals but now it just dawned on you that you have a lot of hot little stressed out molecules infront of you and no hot box to calm them down. The Google gods offer you sanctuary for your little unhappy campers but require a blood offering of 800$ for a little chili pepper kiln delivered right to your door but your all out of juicy virgins to sacrifice. A prayer to the eBay gods yields some hope but WTF do I need a micowave?? More searching and we find a nicely priced unit that runs on 480v three phase goodness but we are not about the life... You get the silly point. I think a fraction of the dodging is actually just some of us allowing all this info to intimidate and confuse us.
Moral of the story you can flame anneal enough to get by practicing techniques and learning the flow of things (that's pun #3 anyone catch #2?) but wear proper protection because things will break and there is potential to really hurt yourself this way, that aside less is more and after your comfy or saved up the green backs get a kiln. Paragon makes a nice kiln imho sc2 model with door (: you can make one for a fraction of the cost of an actual professionally built kiln but that has its drawbacks and should be only considered if your savvy with those kind of things! If anyone needs anything or some help please feel free to contact me here or email nycat247@aim.com I have some experience with electrical systems, controls, heating ventilation air conditioning and refrigeration.
Just wanted to clear that up in hopes to buy us noobs a little slack maybe? If not srry for my .2 wish you all the best and good luck!

[BORO]

This is what came to mind when I read the title to this thread.

Me relieving my "stress" at the end of the night with my one beer reward. This was taken yesterday right before close.
74519

Friday was the first day we were open, and working at the same time.(42Degrees in Lake George NY) We only had the most basic tools, and a sargent torch. No kiln brought to the lake yet. The 3 cups I made had no cracking issues. I'm batch anneling them right now at the old shop. Really wish I had a Bunsen burner , they are cheap, and it would have saved some time during assembly.

When it comes to annealing with a flame, I just think of it like "reverse flashing". As I finish, I switch right to a propane flame, waving the glass in and out of the flame at a even pace. Over a few mins I will continue to increase the time the glass in NOT in the flame. I also like to walk the heat off the piece...... A.k.a. When I heat a cold color tube, starting at one end, get it to glow, then slowly add more and more into the flame. When I flame annel, I do it backwords, one end of the piece getting almost no flame time as I flash back and forth. Then I'm done, put it in a fiber blanket. (The first picture is right at the end, flashing just the foot.)

Each one with glow glass accents , and a 1/2" marble on one side. Any glass over 1/2"? thick, my survival precentage goes way down.
74520

Today....
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New shop, the windows face east. Vermont is right on the other side of thoes mountains.74522

This is Chow, one of the owners. He is making fume spoons with the same "reverse flashing" anneal. He had 100% survival. Only one year torching, very limited amount of torching in that time. Imo, it is do-able even for the less experienced. However I don't think it is a substitute for a kiln. When it's in a kiln, it all shrinks at the same time, squeezing in , (or close to it) I will never be able to replicate a kiln. It creates such a even heat base on the piece, and lets it all cool as one.
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[OrangeSlice]

BoRo, what an amazing view. That looks like a great place to melt.

[BORO]

Hotter than hell in here today... Other shop has a.c. *_*

May be time to go jump in the lake
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No that's not my Coors.... ( IPA 4 life)

[istandalone24/7]

When it comes to annealing with a flame, I just think of it like "reverse flashing". As I finish, I switch right to a propane flame, waving the glass in and out of the flame at a even pace. Over a few mins I will continue to increase the time the glass in NOT in the flame. I also like to walk the heat off the piece...... A.k.a. When I heat a cold color tube, starting at one end, get it to glow, then slowly add more and more into the flame. When I flame annel, I do it backwords, one end of the piece getting almost no flame time as I flash back and forth. Then I'm done, put it in a fiber blanket

that is one of the best "how to"s i've ever read on flame annealing. really good and simple way to look at it. thanks BoRo!

[sredinger]

I have had large 1-1/2 inch and two inch marbles break in two after a few minutes in the kiln. It confuses me why some marbles break while others do not. I suspect that the large marbles I do not finish off with a couple of minutes of final flame polishing are the ones that break. The ones that break have to have super stress inside to completely split-- I can hear them when they go making a "Tink" noise inside the kiln. So sad and frustrating. It might be because I flame off the puny mark and stress out the marble too--- but still-- something is just not right. Next I suppose I should try and expose the large marbles to the flame for a while to reduce stresses.

[dustyg]

I have had large 1-1/2 inch and two inch marbles break in two after a few minutes in the kiln. It confuses me why some marbles break while others do not. I suspect that the large marbles I do not finish off with a couple of minutes of final flame polishing are the ones that break. The ones that break have to have super stress inside to completely split-- I can hear them when they go making a "Tink" noise inside the kiln. So sad and frustrating. It might be because I flame off the puny mark and stress out the marble too--- but still-- something is just not right. Next I suppose I should try and expose the large marbles to the flame for a while to reduce stresses.

A flame-bath to even out the heat throughout the marble is always the next to last step - right before the grabbers, breaking off the final punty, and fire-polishing the punty mark.

[menty666]

I like to give my marble mold a quick flash too so it's not heat sucking cold while I'm flame polishing the last scar

[Neighsicle]

I am currently just getting started, I had been working in a production shop for three years and am just now getting my own set up. I have been making small pendants/sculptures to make back some of my cash to pay for electrician work on getting my kiln wired in, so for now I am just stuck with flame annealing.

I had gotten experienced with flame annealing, it was something I would often do on little side projects, and it would be pretty easy to see what objects and thicknesses it worked on and didn't. Some would crack same or next day, some would crack within a couple of months, and some haven't cracked even up to three years later. After getting accustomed to it, I figured I would have to develop a nice repeatable method. This quicker technique only works for about .25" thicknesses in rod joints, and .50"-.75" marbles. Doesn't work for discs, or thick sculptures with odd forms. Marbles show a unique property in their heat gradient. Discs tend to crack with this technique. I know that this sort of conflicts with most listed annealing times, but it hasn't given me any trouble for quite a while. There are a number of colors that have flame striking temps at about 1100-1000 (Double Amber Purple), so they make good heat indicators. I had to establish that there was a nice smooth gradient to the flame. Going to an all-propane flame where it jumps off the torch, the hottest part is where the blue meets the yellow, this temp is atleast 1150, as it works to both strike amber, and also soften thin sections of glass. I hold the piece here until everything (including the inside of the marble) is glowing barely red. Then, working slowly towards the base of the flame, I hold it at halfway between the base and the blue-meets-yellow point. This finalizes all the striking, and is my soaking temp. I hold until everything stops glowing and then give it a little extra soaking time for about a minute. Then, I move the pieces to just above the base, and hold for about 5 minutes. I then set it aside and let it bench-cool. This has worked great for me so far, I haven't had anything crack yet. I have a few pieces that are still in that "crack in a few months" window, but I suspect they will stay stable.

I wouldn't feel comfortable using the technique on hollow functional pieces, or something with a lot of joints. I do know that with proper technique, flame annealing can make a kiln obsolete. (At the expense of a ton of propane). Think about the work of Blaschka, or older lampworkers. They would flame anneal all their work and it has lasted for decades. Soft glass is also harder to anneal, so I figure it is extra viable for us.

Also, with the whole glass-striking as an indicator thing, does anyone know a color of glass that strikes at 900f?

[Jimi The Don]

buy or build a polariscope

[lhelber]

Don't forget that proper annealing is not just getting a piece of glass to a certain temperature but is also getting it to cool down evenly an at a rate that does not induce any stresses. That is why some of your glass may still be cracking. You got it to temp but the non-evenly shaped items like your saucers are cooling down unevenly reintroducing stress back into your glass. Also most annealing cycles require you to hold the glass at the annealing temperature long enough for the stresses introduced during shaping have had a chance to relax before the cool down begins. Most annealing charts start at around an hour for a proper annealing cycle.


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