Handblown Glass: How It's Made and How to Care for It

Hand-blown glass is made by gathering molten glass on the end of a hollow pipe and inflating it with breath, shaping it by gravity, tools and rotation while it is still liquid. There is no mould dictating the final form, which is why every piece differs slightly from the next.

How is hand-blown glass made?

1. The gather. The maker dips a steel blowpipe into a furnace holding molten glass at well over a thousand degrees and turns it to collect a glowing mass. How much they collect determines the size of the finished piece, and it is judged by eye.
2. Marvering. The gather is rolled on a flat steel surface to even it out and begin shaping it. Colour is often introduced here, by rolling the hot glass in crushed coloured glass which then melts into the surface.
3. The first blow. A short breath down the pipe creates a bubble at the centre. Everything that follows is a manipulation of this bubble.
4. Shaping. The maker alternates between reheating and working, using wet wooden blocks, shears and simple hand tools. The pipe is turned constantly, because glass sags the moment rotation stops. This is the part that looks effortless and is not.
5. Transfer. The piece is moved to a second rod, called a punty, so the top can be opened and finished. This is where the base gets its pontil mark.
6. Finishing the rim. The opening is widened and shaped while hot. A heat-finished rim is slightly irregular and rounded, which is why it feels softer against the lip than a machine-cut one.
7. Annealing. The finished piece goes into a kiln that cools it slowly over many hours. Skip this and internal stress will crack the glass, sometimes days later.

Annealing is the step people are surprised by. A tumbler may take a few minutes to blow and a full night to cool safely. It is also why hand-blown glass cannot be made quickly even when the blowing itself is fast.

How can you tell hand-blown from machine-pressed glass?

• Look for a seam. Pressed and moulded glass usually has a faint vertical seam where the mould halves met. Free-blown glass has none.
• Look at the base. A pontil mark, the small rough or polished scar where the piece was held during finishing, is strong evidence of hand work.
• Check the rim. A hand-finished rim is slightly irregular and rounded by heat. A machine rim is perfectly even and often cut.
• Hold two up together. The clearest test. Any two hand-blown pieces will differ visibly in height or wall thickness.
• Look for bubbles. Small bubbles in the wall are normal in hand-blown glass and rare in factory glass.

None of these are defects. A pontil mark and a bubble are the receipts.

What to look for when buying

Beyond authenticity, there are things worth judging in the shop or in the photographs.

Does it sit true? Slight variation in wall thickness is expected. A base that rocks is not.

Is the weight distributed sensibly? A heavy base and thinner walls is the combination you want in a tumbler. It is harder to make than a uniformly thick glass and it feels considerably better.

Where are the bubbles? Scattered small ones are fine. A cluster near the rim or at the join of a handle is a weak point.

Is the colour in the glass or on it? Genuine coloured glass carries colour through the wall, so it does not fade or scratch off. Look at the rim edge in cross-section.

Our glassware collection is hand blown in India, covering tumblers, highballs, wine glasses, coupes, carafe sets and bud vases. If you are working out which shapes you actually need, our home bar glassware guide goes through it glass by glass.

Can cloudy glass be fixed?

Sometimes. Soak in equal parts warm water and white vinegar for an hour, then wash and dry with a cloth immediately. If the cloudiness lifts, it was mineral deposit.

If it does not shift, the surface is etched. Etching is microscopic damage to the glass itself, usually from repeated dishwashing, and it cannot be reversed. This is the strongest practical argument for hand washing, and it is worth knowing before you put a hand-blown piece through a machine once to see what happens.

Where glass belongs in a home

Glass does two different jobs and they suit different rooms.

As drinkware it belongs to the Social mood, coming out when there are people in the room. As a decorative object it works hardest wherever light moves, which our piece on styling decorative glass covers in detail.

It is also the reflective element in a well-textured room, which means it reads best when there is something matt nearby to contrast with. That mechanic is explained in layering texture at home.

Buying hand-blown glass online

Most of the tests above assume the piece is in your hand. Online, three checks stand in for them.

• Study the rim in a straight-on photograph. A very slight irregularity along the top line is the heat-finished rim doing what it should. A rim that reads as perfectly, mechanically level in every shot deserves a question.
• Expect a sibling, not a copy. With genuine hand-blown work the photograph is representative rather than exact, and an honest listing says so. The piece that arrives will share the design and palette and differ a little in height and wall.
• Check the scale against something. Glass photographs lie about size more than any other material, because there is nothing familiar in frame to anchor it. Find the stated capacity or a photo with a hand in it before deciding.