Books, do we really need them?

The children’s Summer holiday is a fantastic time to have a good clear out of the workshop, done! Fewer distractions as so many people are away. So now I have more space, yippee. New book shelves are already groaning under the weight of my books on glass. I have to admit that I am a hopeless book lover. The smell of a new book, the feel of the new pages and the way it slides perfectly onto the shelf,finding its home between the Andy Goldsworthy,’Wood’ and the Calendar of Saints. The anticipation as we wait for the Amazon parcel to drop in the post box (we have no letter box!) That rare half hour we snatch on the way to the shops as we divert from our food shopping duty and slink guiltily into the bookshop to peruse the art book shelf yet again. Ooo I haven’t got that one,and yet another book finds a new home. The joy of discovering an old bookshop tucked away in a side street. Children raise their eyes to the heavens as I HAVE to pop in. The musty old smell of books transports me back to somewhere in my childhood and I surreptitiously open a book and sniff!
Have I got enough books on glass and art? Of course not I just need a bigger studio to house them all!

Playing with Glass!

It never ceases to amaze me how different 3 pieces of leaded glass can be! All made within inches of each other (well the workshop is certainly not palatial!) Friday 3rd September saw the first of my autumn stained glass courses followed by another on Saturday. I teach 3 student at a time on the leading course. This has turned out to be my magic number. With 4 of us milling around in the studio it’s cosy without being too cramped. Your tuition is almost one-one without the intensity of me looking over your shoulder all the time. Without fail we always ‘click’, after all we are there for the same reason, the love of glass and wanting to try something new.
The day starts with a cuppa and chat. We look at our drawings (or lack of) and decide what we are going to make. I have loads of drawings and inspiration here so there is no problem if you turn up with just your enthusiasm!
Then we get down to drawing our cutline.

This drawing is the guide you will use to cut your glass and to lead it all together. 
It stays with us through the whole process and each line represents the heart of the H section lead. Following this we have a little practice at cutting glass. Its not that easy for everyone but I do have a few different styles of glass cutter and in the end we usually find one which works for you. Of course I am happy to cut for you too, especially the very tricky pieces.

Then we have the best bit of the day ……………LUNCH. By this time you will need a sit down a cup of tea and a chat! If the weather is good we sit in the garden but in the winter we cosy up next to the Rayburn in the house.
The afternoon is a bit more relaxed as we lead the pieces of glass together. I love leading and find this part of the process particularly therapeutic!

Soldering follows this, the waving about of a flame! Do not fear most people find this such fun!!
Then a brief instruction into cementing process which I do for you over the next few days. We also stand about a bit by this time admiring our handy work and chatting to our new friends. The panels below were made on Friday 3rd and Saturday 4th September.
An amazing 86 people have so far made panel with me in 2010. Goodness knows how many chocolate biscuits and cups of tea and coffee have been drunk!!

To Flow or Not to Flow?

Now heres the question…. I am often asked glassy questions, most of which I can have a stab at and reply with a good informed answer. However occasionally I am asked a question, the question, the one I have been asked on many occasions over the last 20 years. “Why is some glass thicker at the bottom? Is it because it flows downwards over the years”?
Well my first instinct has always been to stifle the giggle and then sagely inform, ‘Well no as a matter of fact I believe its the way the glass is originally made”. 
I was asked this very question yet again and felt that now was the time to do a bit more than give an educated guess. Imagine my delight when I found this article. Answering all my queries! Thank you Henry Halem!




http://www.glassnotes.com/WindowPanes.html

No, It Doesn’t Flow
Robert H. Brill, Research Scientist The Corning Museum of Glass July, 2000
Early one spring morning in 1946, Clarence Hoke was holding forth in his chemistry class at WestSide High School in Newark, New Jersey.”Glass is actually a liquid.” the North Carolina native told us in his soft Southern tones. “You can tell that from the stained glass windows in old cathedrals in Europe. The glass is thicker on the bottom than it is on the top.”Now, more than half a century later, that is the only thing I can actually remember being taught in high school chemistry. I didn’t really believe it then, and I don’t believe it now.In the years that followed, I came across the same story every now and then. Most often it popped upin college textbooks on general chemistry. And now, thanks to the Internet, our Museum has received dozens of inquiries about whether or not this is true. Most people seem to want to believe it.
It is easy to understand why the myth persists. It does have a certain appeal. Glass and the glassy state are often described by noting their similarities with liquids. So good teachers, such as Mr. Hoke was, like to quote the story about the windows. As is the case with liquids, the atoms making up a glass are not arranged in any regular order-and that is where the analogy arises. Liquids flow because there are no strong forces holding their molecules together. Their molecules can move freely past one another, so that liquids can be poured, splashed around, and spilled. But, unlike the molecules in conventional liquids, the atoms in glasses are all held together tightly by strong chemical bonds. It is as if the glass were one giant molecule. This makes glasses rigid so they cannot flow at room temperatures. Thus, the analogy fails in the case of fluidity and flow.
There are at least four or five reasons why the myth doesn’t make sense. Some years ago, I heard a remark attributed to Egon Orowan of the Massachusetts Institute of Technology. Orowan had quipped that there might, indeed, be some truth to the story about glass flowing. Half of the pieces in a window arc thicker at the bottom, he said, but, he added quickly, the other half are thicker at the top. My own experience has been that for earlier windows especially, there is sometimes a pronounced variation in thickness over a distance of an inch or two on individual fragments. That squares with the experience of conservators and curators who have handled hundreds of panels. Although the individual pieces of glass in a window may be uneven in thickness, and noticeably wavy, these effects result simply from the way the glasses were made. Presumably, that would have been by some precursor or variant of the crown or cylinder methods. One also wonders why this alleged thickening is confined to the glass in cathedral windows. Why don’t we find that Egyptian cored vessels or Hellenistic and Roman bowls have sagged and become misshapen after lying for centuries in tombs or in the ground? Those glasses are 1,000-2,500 years older than the cathedral windows.
Speaking of time, just how long should it take theoretically-for windows to thicken to any observable extent? Many years ago, Dr. Chuck Kurkjian told me that anacquaintance of his had estimated how fast-actually, how slowly-glasses would flow. The calculation showed that if a plate of glass a meter tall and a centimeter thick was placed in an upright position at room temperature, the time required for the glass to flow down so as to thicken 10 angstrom units at the bottom (a change the size of only a few atoms) would theoretically be about the same as the age of the universe: close to ten billion years. Similar calculations, made more recently, lead to similar conclusions. But such computations are perhaps only fanciful It is questionable that the equations used to calculate rates of flow are really applicable to the situation at hand.
This brings us to the subject of viscosity. The viscosity of a liquid is a measure of its resistance to flow-the opposite of fluidity, Viscosities are expressed in units called poises. At room temperature, the viscosity of water, which flows readily, is about 0.01 poise. Molasses has a viscosity of about 500 poises and flows like… molasses. A piece of once proud Brie, left out on the table after all the guests have departed, may be found to have flowed out of its rind into a rounded mass. In this sad state, its viscosity, as a guess, would be about 500,000 poises. In the world of viscosity, things can get rather sticky. At elevated temperatures, the viscosities of glasses can be measured, and much practical use is made of such measurements. Upon removal from a furnace, ordinary glasses have a consistency that changes gradually from that of a thick house paint to that of putty, and then to that of saltwater taffy being pulled on one of those machines you see on a boardwalk. To have a taffy-like viscosity, the glass would still have to be very hot and would probably glow with a dull red color. At somewhat cooler temperatures, pieces of glass will still sag slowly under their own weight, and if they have sharp edges, those will become rounded. So, too, will bubbles trapped in the glass slowly turn to spheres because of surface tension. All this happens when the viscosity is on the order of 50,000,000 poises, and the glasses are near what we call their softening points. Below those temperatures, glasses have pretty well set up, and by the time they have cooled to room temperature, they have, of course, become rigid. Estimates of the viscosity of glasses at room temperature run as high as 10 to the 20th power (1020), that is to say, something like 100,000,000,000,000, 000,000 poises. Scientists and engineers may argue about the exact value of that number, but it is doubtful that there is any real physical significance to a viscosity as great as that anyway. As for cathedral windows, it is hard to believe that anything that viscous is going to flow at all.
It is worth noting, too, that at room temperature the viscosity of metallic lead has
been estimated to be about 10 to the 11th power, (1011) poises, that is, perhaps a billion times less viscous–or a billion times more fluid, if you prefer than glass. Presumably, then, the lead caming that holds stained glass pieces in place should have flowed a billion times more readily than the glass. While lead caming often bends and buckles under the enormous architectural stresses imposed on it, one never hears that the lead has flowed like a liquid.
When all is said and done, the story about stained glass windows flowing-just because glasses have certain liquid-like characteristics-is an appealing notion, but in reality it just isn’t so. Thinking back, I do recall another memorable remark by Mr. Hoke. One day, our self–appointed class clown sat senselessly pounding a book on his desk at
the back of the room. “Great day in the mawnin’, son! ” shouted Hoke. “Stop slammin’ your book on the desk. Use your head!” That was good advice–no matter how you read it.
Reprinted with permission from Dr. Robert Brill, brillrh@cmog.org

Just checking to see if it works!

Not waving!

Saturday and like all good hard working citizens I should be snoring or reading the paper but here I am struggling with a computer and putting off the moment when I put pen to paper and work out my 6 quotes I have outstanding! The joys of running a business from home are many and varied 😉