Glass: The Alchemist's Art Medium Explained

Many of you know I'm a glassblower, but I'll bet not many understand what glass truly is or that there are many types of it.  In reality, glass is an amazing and somewhat unexpected chemical mixture that results in what's called an amourpous solid.  When I looked up the definition I found that it is used to describe things "without a clearly defined shape".  Anyone that has looked at anything glass can agree, it's found in all shapes, there's no such thing as a glass shape, although there are shapes commonly used in glass for sure. 

Not all glass is equal.  For example, I can't just put a coke bottle in my torch flame and expect it to end well. John tried this once....and it literally exploded everywhere. The photo above is from a customer complaint, as they were expecting the old durability.   The type of glass you see in bottles and windows isn't good enough for pipemaking, which uses something closer to older Pyrex.  I say older because recenty made Pyrex baking dishes are not made with the same glass as old ones, which were known for durability. More into this later.

Glass starts as silica, which is quartz crystal.  Additives are put in to lower it's melting tempurature and improve workabiliy as quartz is very difficult to flame work.  I recently tried to repair an old broken quartz dabbing nail and it was the most difficult thing I've ever had to do in glass.  I have a torch capable, but you essentially have to work it in the flame only and it takes forever.  Anyone that's watched me or any other lampworker blow, the piece is actually out of the flame quite a lot. Quartz in the glass world is referred to as fused  silica, which is honestly what it is.  It has it's useful advantages which make it worth the trouble, like the fact that it's very strong and it has high melting point.  Anyone that's dabbed with plain borosilicate glass knows the fixtures don't last long.  Both of our nails have been cracked for a long time but they still hold up despite repeated daily heating and cooling with a torch. 

The most common sort of glass you come into contact with is soda-lime glass.  This is in drinking glasses, windshields, windows, bottles. It contains: silica, sodium oxide, lime, mangesia and alumina. The melting temperature is much lower and it's texture make it much easier on the artist to work.  A soda-lime art piece is out of the heat source for a couple of minutes at a time when working, something definately not possible with fused quartz. There are costs to these additives, they reduce toughness and thermal stability.  This means anything made with this glass is prone to break if the tempurature changes too rapidly.  It can't really deal with temperatures over 500 degrees before it bursts, literally. Soft glass workers have this issue because their larger pendants and scuptures have a tendency to crack randomly, ruining the piece.Pyrex pans are now made with this because it's cheaper, but I myself have witnessed one of these pans explode when set on a metal surface.  So if you've got a Pyrex pan with pryex in little letters only, be careful when removing it from the oven and never put it into an oven over 350 degrees directly.  If you need to use it at a higher temp, start at 350 and turn it up after you put the pan in.

Pyrex used to make their pans out of what's called Sodium Borosilicate glass, which is what I work with.  The recipe includes silica, boron trioxide, soda and alumina. The glass is less subject to stress from being heated, which makes it less likely to crack from shock.  This is why I can work easily with cold borosilicate wheras the coke bottle exploded on John when he attempted to work it.  Once formed, soft glass generally needs to be remelted down before it can be worked into anything useful. 

Pipemakes like boro because it's easier to work in many ways than soft glass, and it's more durable.  A properly made spoon pipe can be dropped on concrete without breaking, that's how durable it can be.  An old American advertising technique at music festivals was that glassblowers would walk around with a bag or hat of pipes, jingling them around to prove they were strong.  I've dropped many of my own pieces, just to watch them bounce on my concrete tile floor, never on purpose. Things happen in glass, and pieces do go to the floor accidentally every once in awhile, even for the pros.

Artists are also a fan of using lead glass as it's been described as being more "brilliant" than any other glass.  What they mean by this is that it has high refractive index.  It reflects light back to the eye much more than any other type of glass, making it appear more brilliant.  It's also the glass known for it's ringing effect, due to it's elasticity. It's made with: silica, lead oxide, potassium oxide, zinc oxide, aliminum.  These additives make it so it's sensitive to heating.  

Anyone that knows anything about the internet knows that the backbone of the internet as we know it is made of glass. The type of glass is called germanium oxide glass and it's used because it's extremely clear, making it better for light transmission.  When light travels through most other glass, it bounces all over the place making it so the whole glass object kind of lights up.  Fiber optic glass is so clear that light just travels through it freely, making our internet as we know it possible.  It is made with: alumina, germanium dioxide.

The glass you see in household fiberglass insulation and in halogen bulbs is called aluminiosilicate glass.  It's made with: silica, alumina, lime, magnesia, barium oxide, boric oxide.  

John and I learned about a type of glass recently we've never heard of caleld Vycor.  It's not even manufactured anymore although Corning holds the rights to it.  It's a cross between fused silica and borosilicate, making it very interesting to us.  Evidently, you shape your piece out of borosilicate.  After, you treat it with a chemical and the boron trixoide essentially disappears, leaving you with porous fused silica, or quarts.  Heat treat this to 1200 and it'll shrink down, becoming non porous shaped fused silica.  This makes it so the boro worker can make any shape out of quartz with the right things.  Sadly, this glass is no longer being produced and is stupid expensive on ebay.

Glass is an amazing substance coming from a rock I've always had a soft spot for, quartz.  Until I got into this, I never had the understanding that glass is just quartz with additives.  Knowing this, it makes the fact that Acapulco is made of quartz stuffed boulders so much more amazing.  When you think about it, Acapulco is made of glass.

We watched a series recently that I'll link, called the age of glass.  Every time seems to have it's own title, the age of steel, the age of wood ect. The guys from Mythbusters and Corning put this little series together and honesty they're right.  Could you imagine a world without glass?  What would driving  be like? Houses with no windows? No fancy cell phone? No cups to drink out of? See where this is going? 

As I learn more and more about this substance, I get a greater respect for it.  I completely understand why glassblowers are called alchemists.  They put base materials together to get glass.  They add metallic salts and produce amazing briliant colors with them.  One of the most popular American borosilicate color producers is called Glass Alchemy, and it makes sense. 

Next I'll delve into the history more and share that with you, as it's honesty extremely rich.  Glassblowers have been both revered and enslaved for centuries for their knowledge of the craft. More on that later though, stay tuned!