WE ARE GLASS
We start with the raw materials. In this case, that’s premade glass pellets, as Hen Ogledd’s Ann explains: “We buy in our raw, plain glass in pelletised form. When the glass is made from its raw chemical constituents, it takes around three days of heating at 1600°C. Then you’ve got to let that sit so all the bubbles rise out, to ensure it’s in the same condition throughout. We have a mobile furnace, so if we did it that way we’d have to be here three days in advance, burning gas 24/7.” This speeds up the work, but glass is such a good insulator of heat that, even at 1200°C, it takes three hours to get the glass up to temperature.
After the furnace, the tool you’d most obviously associate with glass-blowing is a metal tube, called the iron. The first step is to dip the iron into the molten glass that’s sitting at the bottom of the furnace. This comes out glowing reddish-orange, and you have to keep twisting the iron in your hands to stop the molten glass dripping onto the floor, like honey on a spoon. We take a deep breath and try to squeeze some air down the tube and into the glass. Then we try again, but this time harder; the glass is molten, but it’s still viscous and heavy, and the first breath in takes a lot of effort to break the surface tension and introduce a bubble into the glass.
Now it’s time to add the colours. These come as granules of broken glass, into which we dip the molten glass in the same way you’d put breadcrumbs on a bit of meat to make schnitzel, first on one side to add the yellow granules, then on the other to add the green. This isn’t as simple as it looks, however…
“To make colour, they add metal oxides to clear glass,” says Josh, the other 50% of Hen Ogledd. “The pink colour is made with gold oxide – it’s really expensive. White used to be made with arsenic but it’s now made with tin; blue comes from iron oxide. When you add the colours, it changes the quality of the glass, so the stuff we buy to add colours has to have guaranteed compatibility.
“Each different type of glass has a different chemical composition,” explains Josh, “so it expands and contracts at a different rate. We work with glass that’s 96 coefficient of expansion (COE), which is 96 × 10-27.
“If we were to mix this with bottle glass, that resultant mixture would break, no matter what the rate at which we cooled it down. Because the glass we use contracts as it cools at 96. This contracts as it cools at something like 30, so as the bottle glass molecules contract, they move; these stay in the same place, and that causes internal stress. The forces get so much that it will just explode. If you hold a piece of glass up to a polarising light, you can sometimes see the stresses inside, like petrol on the surface of a puddle of water.”
The granules stick to the molten glass, but they need to go back into the furnace so that they themselves can melt onto the surface of the glass blob. Still turning it round so that the glass doesn’t drip, the iron goes back into the furnace, then comes out when the coloured granules have reached the same consistency as the rest of the glass.
Glass of many colours
At this point, all the yellow is on one side, and all the green is on the other side; now it’s time to swirl the colours around to get a pattern that will look good on your Christmas tree.
Hen Ogledd uses a chair with a flat arm, which can be used to roll the iron back and forth at a constant speed. Keeping the glass moving, we spin the iron with two hands and grab hold of the end of the glass with a pair of tongs (yes, this takes three hands – beginners always need help with everything). The twisting motion gives the glass the swirls and mixes up the colours. It’s a hypnotic motion that looks like toffee or fudge being folded, and looks like we can lean forward and lick it. Obviously that would result in significant injuries, so we resist.
So, the glass literally looks good enough to eat, but it’s still not right:
“With the colours being based on metal oxides, they change colour when they get hot, which is really annoying. So oranges, yellows, and reds all go to a red/black. Blues tend to go to pink and greens stay the same, funnily enough. Whites go clear, and blacks just get blacker and redder. So you can’t actually tell the colour of the piece until it’s cooled down.”
Another quick blast in the furnace and it’s time to give the bauble its final shape.
Great balls of fire
Now comes our favourite bit: smoothing the glass and shaping it to a perfect orb. This uses a specialised tool that’s a block of wood with the shape of a round cavity carved out of it, with a handle, and it lives in a bucket of cold water, for reasons that will become obvious. The hot glass goes in the wooden cavity, the iron spins, and a big cloud of steam comes up from the damp wood:
“When the wood burns it creates a carbon layer, which doesn’t stick to glass at all. And because it’s wet it creates a kind of cushion around the glass. For more complex shapes, we’ll use wet newspaper, which gives you more control, but as it’s only a little touch here and there it doesn’t burn – it just gets a bit warm.”
Hot air
This next bit requires someone who knows what they’re doing in charge, so Ann takes over spinning the iron. We just get to do the essential step of filling the bauble with air. One deep breath and the bauble grows to grapefruit size as Ann spins it to make sure it stays round. Now the thing that we’re making looks like other things that people have made, which is a good sign. It’s time to get the bauble off the iron, but working with glass requires its own logic. Rather than cut the bauble off, we use a tool called a pair of jacks – they look a lot like a pair of shears, with a handle in the middle and two blades that cut into the glass. This looks like it’s cutting, but in fact it’s cooling the glass at a place we can control. This makes it brittle at that point, which means we can break it off.
“To take the piece off the iron we have to make what’s called a necking line, which is where the glass will break away. If we don’t put that line in, it either stays attached to the iron, and then it ends really badly, or it will break off in completely the wrong place and the piece that you’ve been just been working on for an hour and a half will break right down the middle.”
Ann adds a blob of molten glass to the top of the bauble to make a loop and that’s the thing complete. Sadly, I can’t put it in my pocket and take it home, because its still soft, and it’s still hot enough to melt my skin.
“Once the glass is made, we have to put it away in the kiln, overnight. Even though it looks hard, it’s still around 500 degrees. Between 500 and 380 is where glass actually forms its structure; it’s called a neolith. If you wanted to blow some glass and then just leave it out in the air, it would be very susceptible to temperature changes, because the structure of the glass would have stresses in it.
“If you imagine a bauble, inside it’s going to stay hotter than the outside. The outside is going to cool faster than the inside, it’s going to contract while the inside is going to stay the same, which will introduce stresses into the glass. So we have to bring it down nice and gently so it forms properly. We bring it down by around 30C an hour, which means it cools nicely, the glass forms with little to no stress in it, it’s stronger and it can take temperature changes.“
Our final piece is surprisingly heavy, and seems to look different every time we pick it up. It’s not perfect but it’s ours, and it’s a living link back to methods that have been used for thousands of years.
