So we’re going to see if we can apply that to making a Prince Rupert’s Drop in multiple colors.
Do you know what this is? If you don’t, you’re going to be super excited about this video. This is called a Prince Rupert’s Drop, and it’s created by dripping molten glass down into water. The outside of the drop has an extremely high compressive stress, while the inside is in extremely high tensile stress. You can hit the tip with a hammer and it won’t break, and you can even hit it with a bullet and it shatters the bullet. But if you even nick the tail, it explodes.
I wanted to capture that moment, so I cast a Prince Rupert’s Drop in epoxy resin, and then I shattered it. A lot of people watch this video and they ask me if I used the right epoxy or vacuumed off the gases correctly. But one person asked a different question - should you be using epoxy at all? Can you do it with glass?
To answer this question, I went to Orbit’s Hot Glass and spoke to Cal Breed, the man who made the original Prince Rupert’s Drop. He showed me how to heat up the colored glass and make it into pieces, so that we can have multiple tries. Jill, one of the artists there, has a knack for making the colored drops, and she has a higher percentage rate of success.
We’re learning that these artists have a feel for glass in a way that an engineer doesn’t. So we’re going to see if we can apply that to making a Prince Rupert’s Drop in multiple colors. Jill, an apprentice under Cal, has a special understanding of how glass works that she can’t quite articulate. She knows what she’s doing, though. Cal and his wife Kristi wanted their studio to be a place of exploration, where ideas can be tested and knowledge passed down. He explains that glass behaves differently based on its color, and Eric, Lily, and Bodi are all learning from Cal. When it comes to glass, engineers and scientists think about materials in terms of steel and aluminum, but glass is different. It’s brittle and artists are always trying to figure out the point at which it will break or become solid. You’ve seen the graph like this before, right? This is the phase diagram for water. We can boil water from liquid and turn it into a gas, or freeze it and turn it into ice. This is the way I always understood matter to work - you could just move around on this graph, depending on the pressures and temperatures.
Well, yeah, that’s true for water, but that’s not true for all materials. Water has what’s called a first order transition. Let’s make a graph of viscosity versus temperature. If you have solid ice and you heat it up to turn it into liquid water, that phase transition happens very quickly in an extremely small temperature band. This is why water is called a first order transit glass, however, is a second order transition, which means the phase change happens gradually over a wide temperature band. And you would think the graph of that would look like this linear, but it doesn’t. It works like this: cold, solid glass exists up here in the glassy region. But as you heat it up, the glass transition begins and you fall off and the viscosity starts to change drastically, then suddenly it levels off in a rubbery state. This is known as the rubbery plateau. More heat is added and you drop off the rubbery plateau and it starts to flow in what’s called the rubbery flow region. If you add yet more heat, the glass will start to flow like a liquid.
Look at this curve glass. Artists know how to use this curve to make glass do exactly what they want. If you were a glass artist, where would you want to work the glass? For me, it would be on the rubbery plateau. It’s a relatively large temperature range that gives me the same physical properties. That’s pretty cool, right? So as a glass artist takes their work out of the furnace, it’s a certain temperature, right? And then it starts to cool off. And so they have a certain amount of time to work it until it gets all the way back over to the glass transition region. And then they can’t work it anymore and they have to stick it back in the furnace and they move it back down the rubbery plateau, and then they come back and forth and that’s what they’re doing. They’re controlling the viscosity by managing the temperature of the glass. They don’t need to know these graphs to know what they’re doing. They know it in their soul.
Like engineers. We’re thinking about the stress strain curves and we’re like, oh, the glass is going to break here. Well, the glass artist is managing all this with the temperature of the material itself. So they’re riding up and down the curves at all times and they’re just doing it. So what I want you to think about is this curve, because this is how I have to understand it.
The first step for the team is to make the prints. Rupert’s drops. Did it work? Oh, wow. That’s a beauty. Oh, that is so beautiful. Yeah. So now we have this beautiful Prince Rupert’s drop. How do we get this thing in molten glass? The obvious answer is we need it to be transparent. Whatever. Going to hold the glass in. So it needs to be a glass. And so Carl has explained to me that he can’t just go get a glass off the shelf and pour molten glass into it because the temperature difference will cause it to explode due to thermal stresses. So what COW has elected to do is create this glass as he’s getting everything else ready. So it’s going to be hot and the temperatures are similar and it’s going to work out beautifully. And just the process of how he makes this is amazing.
So what we’re about to do, you can’t do unless you have multiple artists doing different parts of the process. Is that true? Yeah. You have to have a team for this. There’s no way you could do this by yourself. Everyone really has a great understanding of the material already, so this is only helping us learn the material better. I’ll stick with you just right. Okay. Sounds good. So the first step of making a drinking glass is to gather glass in the liquid flow region onto a blow pipe. So when it goes into the molten glass and it’s so hot, it’s going to heat up and it’s going to slump over.So we have to be really quick to snap it before that happens.
Cao then takes it out of the furnace, gets the blow pipe and can hold it. He then puts a little bit of air inside the glass and plugs up the end of the pipe with his finger. The heat from the glass makes the gases expand and does all the work for him, using the ideal gas law to blow up the glass. He then heats it shallow to stretch it from the shoulder and make it a cylinder, using the heat differential to shape it. He also rotates it so the part that’s more drippy wants to droop down. He then heats it even shallower and takes his tongs to push down and form the part that’s hotter. He also puts another rod on the other side and breaks off the cap, turning it around and making the cylinder from the inside out. He then lets everyone know where they need to be when because he has to manage the temperatures and the timing. He then gets molten glass in a big ladle and when they set the glass down, the kiln shelf won’t be too cold and thermally shock the glass and break it. When they snap the tail of the Prince Rupert’s drop, they have to be faster because the tail is so skinny and it heats up quickly and slumps over. They have to snap it before that happens, as it is solid, cold, but not a lot of mass. There’s a lot to consider when working with molten glass, such as how quickly heat transfer will take place and the colors used. Karl and his team had to learn this the hard way, but they eventually figured out that blues and greens heat up quicker than reds. After some trial and error, they finally managed to create their desired shape by using graphite mold pieces that Carl adapted to his needs. They also had to practice cutting the molten glass and making sure the mold was closed. The first is that glass art is an intricate process that requires a lot of skill and patience.The second is that glass has a unique way of expressing beauty that can be seen in the folds and stresses of the material.The piece that Karl made is a testament to his skill and the beauty of glass. The first thing Kyle discussed was the second order phase transition of glass, which I hadn’t heard of before, and it’s fascinating. The second thing was about failure, and Kyle has a unique perspective on it. He believes that the moment of failure is a unique opportunity for discovery and learning. He encourages people to keep failing and screwing up until they figure out what is hiding in their intuition. Cal and his team were able to figure out how to make a blueprint, cast it without melting it, and even create polarizing filters. Kyle asked Cal if he would be willing to sell it, but Cal said no. Kyle then asked Cal to put it up on his website without a price, and Cal agreed. Kyle was so impressed with the object that he wrote an 11 year old email to Cal offering to help promote his website and work. If you’re interested in seeing what Cal has to offer, go check out his website [Cal Breed dot com](Cal Breed dot com). Have a great day!