this bird is a jerk.
Suddenly Gbird pops up again and I realize that this is real glass people are playing with all willy nilly and I know enough about glass to get concerned and my face ends up a little more like .....
So, to do my part to keep your bodies and rooms safe this post is all about trash glass...because let's face it...while Delphi and Bullseye art glass is fantastic it's not exactly in the budget for your average bear to do on any real scale. Reclaimed glass on the other hand is dirt cheap. Hopefully it helps you understand more about what's going on in that big bad kiln when making the birds and helps you bird more responsibly (or even those oven baked marbles if that's your thing).
what you need to know about trash glass (and most glass)
Toxins
Those sweet super cheap fishtank marbles you got from Dollar Tree. You know the ones...flat side, net bag. Yeah those. Those were made in China. Maybe. Or maybe they weren't. Now, lets set aside for a minute that they're most likely painted because cobalt (the stuff most blue glass is dyed with) is hella expensive and focus on just the glass. Overseas manufacturers have no oversight especially on things they are sending to the U.S. Dollar Tree glass will usually have lead in it and when I say usually I mean like 95% of the time. On it's own, the lead in the glass isn't a fabulous thing but it's probably not going to do much since it's trapped in the glass and you're not going to be constantly touching those fishtank marbles. However, to get the marbles high enough for a full fuse so that jerk bird can adorably perch next to the "water" you have to liquify the glass thus releasing lead into your air, your kiln, and anything else in it going forward. If you don't believe me take a second and google Dollar Tree and lead. I'll wait. If you don't know lead is bad for children and that they are especially vulnerable please stop teaching and read a book (any book) about it.
But I didn't get mine from Dollar Tree you say! I'm fancy! I got it at Hobby Lobby! Sorry charlie but by the time you shell out for Made in USA fishtank beads you could have already bought actual art glass and would know the COE on it. More on that in the next section...
COEs
A COE tells you how fast a piece of glass expands and shrinks when it's heated. COEs can and do vary widely. Art glass you order from a catalog will be in the 90s while a float glass window will be in the 80s. Pyrex is usually in the 30s. Manufactures adjust this to help the glass stand up to different uses or to make it cheaper to produce. Glasses with different COEs should not be fused together (heated) because the results aren't good. Watch this Tommy Boy clip and imagine Richard is a lower COE than Tommy...that's basically what happens on a molecular level:
Types of Firing
When you fuse glass as an artist you decide if you want to do a slump, a tack fuse, a contour fuse, a full fuse, or completely liquefy the glass for a pot melt.
Once you've decided a temperature you have to decide a soak and anneal time. Soaking is how long you keep the glass at temperature and annealing is how slowly you bring it down. Soaking works with your temperature to determine what kind of fuse you end up with. Anybody who has ever tried to bake a cheesecake and keep that delicious bastard from cracking has run into this problem. You can even try it yourself. Bake one cheesecake for an hour on 350 and another at 300 for two hours...in both cases you get a finished desert and may even get a similar consistency. However, take either one of those and dump them immediately into a freezer (because it's Thanksgiving and you waited until the last minute) and suddenly you have a gigantic fissure in your delicious treat....but let it cool in the oven and you're far less likely to get one. Leave the hotter cheesecake in for two hours and you sir have a burnt cheesecake and a very unhappy husband. For those of you that have done the oven baked marbles to get them all cracked an sparkly you did the same thing. You skipped the annealing to create a controlled cracking.
So how do I know what firing schedule to use? The COE tells you that, just like Tommy's waist measurement lets the clerk at the store know what size of coat he SHOULD be wearing. If you google a firing schedule always make sure that its one meant for recycled glass not one for art glass. Glass With a Past is a great blog to start at. When I do recycled glass I start with a firing schedule that I know works, I ALWAYS ALWAYS fire to a tack fuse and then observe the results. If it's not fused enough I can try again.
So I can't use dollar tree marbles and make that glorious bird?
Yes and no. As long as you are using glass from the same object and fusing it to parts of itself you are golden...for instance these ornaments made by smashing up a wine bottle and arranging the pieces into a shape. You are totally cool with those and no fat guys in little coats are going to pose a danger to your students. If the glass is especially cheap or already once recycled it may divitrify and get a permanently frosted look which could equally add to the winter mystique. Again, make sure it's glass made in the USA if you're using it with kids.
You cannot fuse pieces of two different glass objects even if they came in the same package. Just because I buy a six pack of...um...rootbeer....doesn't mean that all six bottles came from the same batch when they were made before they got to the bottling company. Most bottles will be stamped on the bottom with a number and if all that info matches up you are *probably* alright to mix them as long as they are from the same package. I wouldn't go back and get another sixer a month later and start mixing those bottles willy nilly. At that point the only safe route would be to Hulk Smash the glass using a steel mortar into ridiculously micro pieces and fuse them into a solid sheet. It's not an activity that's safe for a kiddo of any age and most of use don't have time to do four firings per project. So, if you do the bird you can use one huge marble all by itself but you cannot toss in a few. China made glass from the Dollar Tree isn't exactly purchased for it's stellar quality control and I've had as many as six different COEs in the same bag. Personally I hooked up with our recycle center and just got blue wine bottles to smash and place since you don't know if the china glass is dyed or actually blue to begin with. (Just don't mix the bottle pieces from different ones)
You also cannot fuse glass over glaze. Glazes are glass and like glass have their own COEs. There's more to it but your eyeball are probably pretty close to falling out and we don't have time for that can of worms. Just trust me OK? Glazes are essentially glass and they have other chemicals in them to make the colors and sweet bursting glazes we all know and love. Inclusions or contaminated glass can cause all kinds of crazy effects.
Always fire glass on a shelf with at least three layers of kiln wash. If something does break free it won't stick to your shelves. You also need to make sure there's not any chips or pitting on the shelf that would cause an undercut and get the glass stuck.
Lastly, reclaim any and all glass. Wine bottles, spaghetti jars, broken windows...go nuts! If it has a color that strikes your fancy, follow the guidelines, and fuse away! Only three types are off limits if you are doing it with kids:
1. Tempered glass from car windows: too much shrapnel
2. Specialty coated glass like UV or tinted: no telling how they behave and see above about toxins
3. Antique glass or any type of crystal: may contain lead
Questions? Comments? Hit me up below. I'm pretty new to this blog thing and would love your feedback.