Kilns deserve a blog post on their own which is why I’ve devoted Part 8 of the Studio Set Up blogs to the topic of “choosing a kiln”. I have finally updated all the photos for this blog post (as at 5 October, ’15). In part 7 I discussed the different tools you will likely purchase as your bead making skills improve and evolve.
There will come a time where the beads you make suddenly start to look so good that you will want to wear them and when you do, the compliments and queries about where to buy your jewellery will start to roll in.
Sure, everyone is proud of their first efforts but it wasn’t until my 70th even nearing up to my 100th bead that my artistic style really developed and talking with other artists, this was about right for them too. About that stage of your bead making career you should consider purchasing a kiln to ensure the longevity and saleability of your beads. For some people it might be three months into bead making, for others three years. Yes, you can get away with not annealing your beads, ancient beads are popping up everywhere thousands of years old and they weren’t properly annealed and are still in tact. Whilst a round or stubby cylinder bead is less likely to crack than any other shape and you can wear these beads without much fear of them cracking, other bead shapes require annealing. Glass is a fragile product and annealing takes away some of the fragility.
Why annealed beads are important for jewellery makers
So what’s with the whole annealing thing anyway? Why do glass workers need to fire their beads if they want to sell them? That question has been answered in detail through this wonderful blog by Everlyn Durberry.
If you are going to sell your beads, anneal them properly in a kiln to guarantee your work.
In short, if beads are butted up against other glass beads or the beads are in a bracelet which gets a lot of knocks, the chances of glass beads chipping and cracking are pretty high if the beads are not kiln annealed. Most mass produced beads from China and India are not kiln annealed, which is why you’ll often see broken and chipped beads in jars and containers in bead shops. When you raise glass beyond it’s stress point and hold it at a set temperature for about an hour, something magical happens; glass becomes stronger and more durable. Round glass beads will bounce off concrete without a chip, scratch or fracture line. I’ve got a necklace full of raised dot beads that I accidentally dropped, they bounced off the concrete and scattered all over the floor. That was five years ago and the necklace is still going strong. However, glass is glass and whilst round beads are more durable than any other shape if you aren’t careful with your beads they will break if dropped no matter how well annealed they are.
If you’re intending to sell your glass beads to other jewellery makers, you want to guarantee your work and they want to be able to guarantee theirs. If you’re making jewellery to sell, the same principle applies, kiln annealing properly is important because it’s your quality guarantee.
What is the difference between annealing and flame annealing?
Annealing is a term used in both metal and glass industries. When you anneal an object you are slowly raising the object in temperature to just beyond it’s “stress point” – which is a type of melt point that removes any internal stresses within the object. The idea is to hold the object at just beyond this stress point for a period of time to remove any pressure inside the object. Then the item is left to cool down very slowly and this action will strengthen the object and provide it with long term durability.
Flame annealing is the technique of heating the bead at the end of your flame (increasing the propane slightly for a hotter flame) until it is lightly glowing red to remove any stress put into the bead, it is a type of annealing but it is not as good as putting the bead into the kiln.
If you have a kiln with a bead door, you would pop the bead straight into your kiln (which will be standing by at a hot holding temperature) when you’re done working for the day, you will set the kiln into it’s ramp up to anneal temperature and ramp down mode.
If you are batch annealing, you will rotate the bead out of the flame until it loses it’s glow and then place it in a fibre blanket or heated vermiculite to cool down slowly. After which it will go through a more strenuous annealing cycle once it has cooled down. When you have made a lot of beads and they’re all cooled down slowly in vermiculite you will run your kiln through an annealing cycle.
Here’s the thing with kilns, like torches, you have to find one that fits you. Kilns can be made from fire brick and/or fibre blanket and lampworkers need to get one with a digital thermostat controller otherwise you have to spend all day babysitting the kiln temperature. Try and get a kiln with a bead door to save yourself having to batch anneal. I bought a “batch anneal” kiln because at the time they were much cheaper than those with a bead door. I don’t mind having this sort of kiln. I can use it for multiple purposes like slumping cabs and fusing.
At the end of the day you’re going to buy something that fits your budget. In the back of your mind you should be looking to buy a kiln in a size that suits your needs with a quality digital controller that can be programmed. That may mean you get a kiln with a bead door and a fancy controller that can be programmed in a number of ways. However, if you don’t have the money and you cannot afford the bead door luxury and you think you will be buying a kiln for batch annealing with a simple controller, read on. I talk about my experiences batch annealing.
To buy or not to buy a kiln
If you flame anneal and cool down your beads slowly they shouldn’t break and you can wear them (I wouldn’t sell beads that aren’t fully annealed). If you have been given a kiln or you bought one with your torch, the best thing you can do is follow the digital controller manufacturer’s instructions to set the ramp up, hold and ramp down program (if you can’t find the instructions, google the brand; a lot of manufacturers have their instructions available for download in a .pdf format).
If you have a pottery kiln that doesn’t have a digital controller, don’t risk firing your beads, you could slump them, or not actually anneal them properly. You can get pottery kilns altered with a programmable digital controller (links to the bottom for Harco controllers in Australia). There are kiln firing schedules for glass beads available on the internet. I have a basic one listed below, which you can modify to your needs. When I say modify, what I mean is, different types of glass require different annealing schedules. For instance, my schedule is for COE104 glass, but you will need a different ramp and anneal schedule for Bullseye COE93, Satake (Soda Lime) COE113, Satake (lead) COE120, Gaffer COE96 and etc. To read more about different brands of glass, check out this detailed blog post by Robin Snuttjer.
Is my annealing good enough?
Kilns are used to raise the temperature of a bead and hold it for a length of time beyond it’s stress point to eliminate any hidden stress fractures. All glass kilns do this, no matter the type. Firing your beads in a kiln to a proper firing schedule guarantees long life of your beads. The general consensus by lampworkers is that the best way to make sure beads are strong is to go from “flame to kiln”. I don’t necessarily agree that it is the best way to fire your beads, but it’s the easy hassle free way. “Flame to kiln” certainly eliminates the risk of breakage from improper flame annealing.
“Batch” annealing means you have to flame anneal properly because you will be cooling your beads down slowly first. Then you need to be careful about putting your beads into a fibre blanket or pot of vermiculite. “Flame to kiln” means you are less likely to crack beads from cooling down too fast in vermiculite or a blanket. Both “flame to kiln” and “batch” annealing methods will anneal your beads properly. “Flame to kiln” eliminates the cool-down step which is where most errors are made. If you are careful and patient, “batch” annealing will be fine for you. Don’t think that if you can’t afford the super duper expensive kiln your beads will somehow be less than wonderful. If you have a lampworker friend nearby you can always send your beads to them for batch annealing whilst you save up for the kiln of your dreams. That way your bead sales can help fund your new kiln purchase.
What is “strain” or “stress” point temperature and why is it important?
I work primarily in Soda Lime glass COE104. If you are working with lower coefficient glass, annealing temperature will be higher.
As a general rule of thumb COE104 glass will anneal at 515 degrees celcisus (960F), this means that if you are using a kiln with a bead door you will want to “garage” the glass between 30-40 degrees lower than your anneal temperature to remove any stress in the glass. So anywhere between 920-930F and about 485-495C should be your garage (strain) point. Bear in mind that I make beads up to 4in long and up to an 1in wide so I do work at the higher end of the firing scale, also my kiln is huge.
If you are batch annealing, depending on your controller you will be able to ramp up, stop at the garage temperature (strain point), then ramp up to the annealing temperature for an anneal cycle. (My kiln controller cannot do this, so I must flame anneal carefully before putting my beads into a straight ramp to annealing temperature).
Soda Lime glass is usually annealed for an hour at 515c, but you can raise the anneal temperature slightly and drop or increase hold times depending on your kiln size and bead size. If you make large beads, it’s always better to slightly increase the anneal temperature to accommodate the thickness of them. Or you can go the other way and increase the annealing time. (I prefer to go slightly hotter and anneal for a little longer – only an extra 10 minutes). You don’t want to go beyond 545 degrees celcius for COE104, because raised designs, faceted and pressed beads will lose their crisp edges as Soda Lime will begin melting beyond that temperature range, if you are using Satake glass pay particular attention to annealing temperatures as it is much softer than Effetre.
For those of you that have kilns with controllers that can cope with stepped programs, one other trick is to bring the kiln out of anneal and stop it for an hour at the strain point before full ramp down. The idea is that with larger pieces of glass art, the second stop at the strain point puts the kiln into a position where the heat is evenly distributed and allows for any stress put into the glass that was not removed the first time (before annealing) to be removed.
But I heard that you can’t encase this glass?
For temperamental glass (glass in the 104 palette that appears “incompatible” when encasing it) the advice from glass manufacturers is to raise your anneal temperature by a few degrees and increase the anneal time by 5 minute intervals. For instance, so many people tell me that they can’t encase CiM colours and I find that to be not quite accurate. Some CiM glass cannot be encased at all, just like some Effetre and some Vetrofond (and so on). However, most of it can be encased just fine when you increase your temperature and soak times. I never have the issues that others have with CiM because my kiln runs a bit hotter and longer than is necessary to anneal glass.
There is no “set and forget” scheduling if you’re mixing up brands of glass and changing your style around. There does need to be a bit of flexibility on your behalf to be ready to fiddle with your kiln controller settings if you decide to go suddenly from making very small beads to large ones, or to encasing beads when you didn’t encase previously. Like baking a cake, each oven is different, each cake is different so you will need to adjust your firing schedule to suit your purposes.
What is “flame annealing” ?
Flame annealing is the practice of heating the bead up evenly at the very tip of your flame to distribute heat evenly through it before putting the bead away into a kiln, fibre-blanket, pot of vermiculite or pot of annealing bubbles. Some artists like to turn up their propane slightly to do so. I am in the habit of keeping the flame neutral so that I do not have any unintended reactions occurring in my finished design. It is extremely important to flame anneal for those of you who are “batch” annealing. Missing this step means that you will get beads cracking in your cool-down phase. I rotate large beads for up to five minutes at the tip of my flame before garaging them in vermiculite. If I forget or think I can wing it on a small bead or do not flame anneal a large bead for at least five minutes, its a certain guarantee that I will develop cracks in my beads.
My kiln firing schedule
After my beads have been flame annealed then cooled down slowly in vermiculite. I pop a big batch of them all into the kiln ready for kiln annealing. My kiln has a ramp up schedule of 5.5 degrees celsius a minute (330C an hour), holding at 45-60 minutes (depending on the bead sizes, I run big beads longer) at 535 degrees celsius (995F) before ramping down at 2.5C a minute (144C an hour). This isn’t a programmed ramp down as my controller cannot do that. Once the anneal temperature is reached my kiln will stop heating and cool down very, very slowly. I usually just let it run overnight and then turn the kiln off in the morning. I run my kiln slightly hotter because my kiln is so large, I found that a 515 annealing temperature was too cool for both the beads that I make (usually really big beads) and the size of the kiln.
Problem shooting beads breaking from stress fracture
One day I sat around and measured the rate the kiln lost heat because I was trying to figure out why a lot of my beads were cracking. I worked out that one reason was because I was not flame annealing properly, I roll my bead at the end of the flame for a good 2-5 minutes before putting it into a pot of heated vermiculite now. Flame annealing is my guarantee of reducing stress fractures in long and thin beads, pressed beads and shaped beads (like “Goddess” beads). The other part of the reason for my bead breaks was the kiln schedule I was using. I had programmed a stock standard schedule that I found on the internet, but what I didn’t take into consideration was the fact that my kiln is SO HUGE that the firing schedule was not annealing my beads hot enough or long enough. So now, I run my kiln slightly hotter than most bead firing schedules you will find online to accommodate the quirks and size of my kiln. I’ve drop tested a lot of beads since changing my program to the one specified above and I’ve had no breaks since. If you have a big kiln (the inside of my kiln is 40cm x 40cm x 40cm) go with a slightly hotter anneal temperature and soak for 45-60 minutes for every inch of thickness in your bead. For example, my four inch long by one inch wide barrel beads anneal for about four hours. You cannot “over anneal” your beads, so it doesn’t matter if you also have half inch round beads in with the big four inch beads. If you want more information about glass annealing, I recommend reading Bandhu Dunman’s Contemporary Lampworking books.
If you are having problems with beads cracking when you accidentally drop them or even after a few months of wear, look at how you work before going out and buying a new kiln, or blaming a particular brand of glass. The artist puts stress into the glass, we can remove the stress if we change some elements about how we work. The kiln schedule can remove a lot of stress if you are stopping at the strain point for long enough before going into an anneal cycle. Annealing cannot remove the inherent stresses in badly constructed beads, beads with bubbles along the length of the mandrel hole (a poorly made first wind), beads that have been allowed to cool down too quickly outside of the flame, beads that are too thin on one end, beads that you have let the ends go cold on, will all have a lot of internal stress. Any of these severe internal stressors will eventually crack the bead.
Things to consider if you are getting a lot of cracked beads
1. Am I putting my bead away too cold (even if you are going flame to kiln, putting beads away too cold will result in a lot of stress which means cracks down the track). Beads should slightly lose their glow before being put into a kiln, vermiculite or blanket. (I put the bead under the desk in the dark to see if the surface is still glowing, if you put a bead into vermiculite (or fibre blanket/bubbles) too hot, these products will stick to the surface, distort or imprint on the bead.
2. Am I flame annealing and keeping the bead warm as I work? Beads heat from the centre outward, the edges of beads get cold before the middle (yes, even on a round bead) Beads with ends that are rapidly colder than the rest of the bead will crack if they go into a pot of vermiculite. So be mindful to roll heat through a bead as you’re working on a design. If you’re going flame to kiln, you can probably get away with having cold ends.
3. Is my kiln temperature right for the beads I’m making? Most of my beads range between 1in and 3in. I make big beads and big beads need a slightly higher anneal temperature and anneal soak length. I still make mistakes though, recently a very big bead came out of the kiln cracked and I know that it was because it cooled to quickly coming out of the program. This is a limitation with my kiln, I cannot hold at a second strain point.
4. Experiment with your controller and get to know your kiln. Keep notes and test your kiln regularly, you may get cold spots in it.
Batch Annealing Overview
Batch annealing offers the same durability as flame to kiln annealing. Round beads that are flame annealed and cooled down properly will last a long time as they are. If you have purchased a kiln with no bead door (like I have) you will be batch annealing your beads because you cannot go from flame to kiln. This means you will need to purchase a fibre blanket or crockpot and vermiculite. Vermiculite is a natural insulator and it’s very cheap. It’s great for slowly cooling beads down in. I prefer vermiculite to a fibre blanket and I don’t use annealing bubbles because they’re hard to get in Australia, but my understanding is that they work in the same way that vermiculite does, with less dust. I also prefer to have my vermiculite heated up as I am less likely to have beads cracking in warmed vermiculite.
The stuff is mostly sold in 100litre bags, whatever you don’t use can be mixed into your potting mixes or used for hydroponic cultivation (it also absorbs water and can be used to keep plants hydrated). Some companies sell vermiculite in a small size bag, always purchase a small grade size of vermiculite (its too hard to bury beads in big chunky vermiculite) and find out if your bag has been sieved, to ensure minimal dust. I put the crockpot onto high before I start my torch session (vermiculite absorbs moisture, so heating it up will remove moisture).
After the torch session is done from high I’ll turn it to medium for an hour and from medium to the off position. It takes about 4 hours to go cold. I then store my cooled beads in my kiln, when it’s full I’ll run the annealing schedule. Vermiculite is a natural product and isn’t hazardous to your health if used sensibly, just make sure you get a small size with low dust. DO NOT peek at your beads once they’re in the vermiculite until it is completely cooled down. Peeking at “warm” temperatures to us, will almost certainly put stress into the bead and lead to cracks. (I used to peek, but now I don’t too many beads have cracked on me due to impatience).
The very blunt (but truthful) pro’s & con’s list of “batch” annealing
- I usually run my kiln at the end of a week with 30 or 40 beads, this saves on a lot of electricity. Pro.
- I didn’t buy a fibre blanket, but that is one method of cooling beads down slowly. Kilns usually have fibre blanket or fire brick in them, fibre blanket and vermiculite is inexpensive. Pro.
- Another method is the crockpot full of vermiculite. I can set the crockpot to heat the vermiculite, guaranteeing a slow cooldown for my beads. I found a new (old) crockpot in a junk store for about $10.00. Pro.
- Flame annealing beads and cooling beads down slowly in a crockpot or fibre blanket offers some durability and for round beads, this is actually enough for them to last, well, indefinitely. (Ancient people didn’t use sophisticated kilns and archaeologists are pulling up glass beads all over the place. Food for thought!) Maybe Pro?
- Batch annealing means you have to actually wait until there is enough beads to warrant running the kiln. This also means you have a silly amount of beads to clean at once when it’s done. (ugh, I hate bead cleaning). Con.
- Multi program controllers and kiln annealers are expensive, a good quality second hand one will set you back at the least $800.00 AUD (that is if you’re lucky enough to find one with a controller and a bead door). You’re more likely to be paying upwards of $1800 AUD for a kiln with a multi program controller and bead door. Con.
- Fibre Blankets and Crockpots rely on the bead having a lot of internal heat. Long or thin beads crack more easily because the heat is not centred in one place, so they must be flame annealed carefully (which can alter the composition of some glass types, that is, you’ll see noticeable colour changes or reactions happening some times). Maybe Con?
- If you don’t flame anneal properly and then put the bead away in the blanket or vermiculite a cold spot could develop a crack and ruin your bead. Con.
- You can’t disturb beads once they’ve been put away into a fibre blanket or vermiculite. Jostling them about to fit more in, will more than likely introduce a cold spot. When I’ve made a lot of beads and I’m running out of space in my crockpot, I forget this basic rule and always, I’ll get a bead with a crack (bugger my impatience). Con.
If you read through that list and thought the fuss of batch annealing is not worth saving a few hundred dollars, then I recommend getting a kiln with a bead door. I will always keep my big batch anneal kiln, but I certainly do want a small kiln with a bead door to sit on top of it for the days that I make hugely elaborate beads and want them to survive. Hugely elaborate beads, like large “Goddess” beads don’t have a good life expectancy in a fibre blanket or vermiculite if you don’t flame anneal well. The uneven heat within a bead like that means it is very likely going to develop a stress fracture, you really must be consistent with flame annealing.
Kiln electricity usage
Kilns are expensive to run, they use up a lot of power. This might be very important to you if you’re an “off grid” person. Most bead makers distinguish between a true kiln (one that can anneal, slump, fuse and tack glass) and annealers (can anneal only, that is; bring glass up to it’s stress point and then cool down) If you have an “annealer” running for a long torch session whilst you “garage” your beads in it, then set it through an annealing session you will see a big spike in your electricity bill. The other rule is, the bigger the kiln the bigger the electricity bill. When I had my studio in my home. Running the kiln a few times each month saw my electricity bill doubled. I was a bit surprised actually at how much power a kiln uses, so I make sure that baby is full before I run it these days. There are some kilns that operate like an annealer (that is, they have a bead door on them and will hold for long periods of time at a predetermined temperature) but can also slump, fuse and do all the other things a bigger kiln does. These are the most desirable kilns on the market because of their compact size and versatility.
How to stop glass “kiln striking” in an annealer type kiln.
One other difference between batch annealing and flame to kiln annealing is that you can overstrike certain colours (particularly silver glasses) in annealers that are garaging beads for a while. The only way to get around this happening is to make test beads up to check how much flame striking is needed before going into the kiln. Just make a few small beads in the colour you want to experiment with and try them out at different strike ranges, then pop them all in the kiln. Try to keep track of how much flame strike was on each bead. Make a chart or use a permanent marker on the end of the mandrel to colour code the beads to identify how much a bead was struck before being put into the kiln. With this way, you can guarantee the colours you want in your silver glass beads.
Silver glass manufacturers Double Helix, Striking Colour (Unfortunately the owner and manufacturer of Striking Colour was in a terrible motorcycle accident and has not been able to produce glass for some time) and R4 or Precision104 as it’s now known suggest doing this exact technique on their respective websites and they also offer tips and advice on different annealing cycles to try for certain glasses.
Kiln Manufacturers (kilns with bead doors)
(Devardi annealers only anneal beads. Several people have them and the warning is to get it’s heat range tested by an electrician. Mark the dial with the anneal point so that you do not accidentally melt all your beads flat).
Karma Design Studio
Lastly, think about what you make. If you’re mostly a bead maker getting a kiln with a bead door is probably the best option and its better to save up for it. If you want to slump and fuse, find a kiln that can do that and maybe forgo the bead door. If you’ve been given an old ceramic kiln, it’s salvageable by getting a controller fitted to it. If you bought a kiln years and years ago and are thinking of an upgrade, then I hope you found what you needed here.