Hand-blown glass: how it is made, where it comes from and how to care for it

By Tiago Reis, co-founder of Ra-Ro · View profile

About a 5 minute read

There is something odd about glass that has always struck me: it is everywhere, and almost nobody looks at it. Windows, screens, glasses, windscreens. It was made for us to see through, not to see. So when a piece of glass makes me stop, my first question is not what it costs. It is who made it, and how.

Hand-blown glass is glass shaped by breath and by a glassblower's hands, one piece at a time, without pressing machines. It is made by gathering molten glass on the end of a hollow metal blowpipe and blowing through it until a bubble forms, which is then shaped with simple tools, heat and gravity; finally the piece cools slowly in a dedicated kiln so it does not crack. In Portugal the great centre of this tradition is Marinha Grande, in the district of Leiria, where there have been glassworks since 1747. At Ra-Ro, blown glass comes from Samuel Reis, who works alongside master glassblowers and gives his glasses and jugs the shape and grain of heartwood.

Glass is, at heart, melted sand. Mixed with soda ash and limestone and fired at over 1000 ºC, it becomes a thick, glowing mass that behaves like warm honey. Glassblowing is more than two thousand years old and has changed very little. I like that. It is not a tradition kept behind a museum case; it is a gesture that still works because nobody has come up with anything better.

How is hand-blown glass made?

The glassblower dips the tip of the pipe into the furnace and gathers a gob of glass, turning constantly so it does not drip. He rolls it on a smooth metal plate to even it out, blows to open the first bubble and reheats the piece as often as needed. Then come the tweezers, the shears and the wet wooden blocks, and the piece moves to the punty, an iron rod attached to the base, while the rim is finished. Last comes annealing, hours in a kiln where the glass cools slowly. Without it, internal stresses would make it crack.

What impresses me most about blown glass is that every move depends on the temperature of the glass, and that temperature changes every second. It is teamwork and it takes time, which is exactly why two identical pieces are so hard to make. Once you understand that, the small differences between two glasses of the same series stop looking like flaws. They start to look like a signature.

Portugal has made glass since the 15th century, but it was in Marinha Grande that the craft grew. In 1747 the Irishman John Beare set up a glassworks there, and wood from the Leiria pine forest came to feed the furnaces. In 1769, with the backing of the Marquis of Pombal, the Englishman William Stephens founded the Royal Glass Factory of Marinha Grande, and the town became known as Portugal's glass capital. Workshops in the area still blow glass by hand alongside the industry, and that deserves saying: some people keep choosing the harder road.

Samuel Reis and glass that refuses to be invisible

This is where Samuel Reis comes in, and he is the reason I wanted to write about glass at all. Heartwood is the dense, dark core of a tree trunk. Samuel takes a material designed to disappear and gives it the grain of that wood. The result is blown glass that gets noticed instead of being looked through. I really like this idea of showing the glass instead of hiding it. And I like something else: Samuel works alongside master glassblowers, which means each piece is his and also belongs to the people who have mastered the furnace and the pipe for years.

From the same series come the Heartwood Glasses, a pair made for the drinks cabinet, and the Heartwood Glass Jug, which does on the table what jugs rarely do: it draws the eye even when empty.

How to recognise and care for blown glass

There are simple signs. Small differences in thickness, height or shape between pieces of the same series. Tiny bubbles trapped in the glass, which are not flaws. On the base, sometimes, the punty mark, where pressed glass would show mould lines on the sides instead. But the most reliable sign is still the human one. A designer piece has a name and a workshop behind it. When nobody can tell me who made a huge run of perfectly identical glasses, I get suspicious.

As for care, blown glass asks for little, but it does ask for attention. Wash it by hand with warm water, mild detergent and a soft sponge; the dishwasher can cloud the glass, and pieces knocking together chip thin rims. Avoid thermal shocks, such as moving a piece from hot water to cold or pouring boiling liquid into a cold glass. Dry it straight away with a lint-free cloth and, for limescale, soak the piece in water with a little vinegar. Store it upright, with space around it. It sounds like a lot of fuss for a glass. It is simply the respect owed to something somebody made with their breath.

Samuel Reis's pieces are available at Ra-Ro on their own or together in the Heartwood Pack. To get to know the region where Portuguese glass grew, read Estremadura: from Óbidos to Nazaré; for ideas on where to put the pieces, see How to decorate your home with Portuguese crafts.

Frequently asked questions

How is blown glass made?

Molten glass is gathered on the end of a hollow pipe, blown into a bubble and shaped with tweezers, shears, wooden blocks and heat. The piece then cools for hours in an annealing kiln.

Where is glass blown in Portugal?

The historic centre is Marinha Grande, in the district of Leiria. It has had glassworks since 1747, and the Royal Glass Factory was founded there in 1769.

Can blown glass go in the dishwasher?

It is not recommended, as the glass can cloud and thin rims can chip. Washing by hand in warm water and drying straight away is best.

Are bubbles in blown glass a defect?

No. Small air bubbles are normal in handmade glass and help tell a blown piece from a factory one.

Who makes Ra-Ro's Heartwood glasses?

Samuel Reis, who works blown glass with master glassblowers and gives it the shape and grain of heartwood.