How to Use Tile Nippers to Cut Mosaic Glass

Reach for wheeled nippers. The blunt-jaw kind are built for porcelain, stone and ceramic, and they will crush glass rather than cut it.

Two small carbide wheels do the work here. They press in and start a break instead of shattering the piece, which gives you a cleaner edge and far more say over the shape. The wheels also rotate, so when one spot dulls you turn them slightly and carry on.

Hold the tile against the wheels and cup your free hand loosely underneath and around it.

Glass throws shards when it snaps. Cupping catches them in your palm instead of sending them across the floor, and it stops the cut piece skittering off the bench. It also keeps the tile steady through the squeeze, which matters more than it sounds: a piece that shifts mid-cut breaks somewhere you did not intend.

Start at the edge. Bring the wheels in a short way from the corner, cup your hand, and squeeze once and firmly.

Edge cuts break the most predictably and make the least mess, which is why they are the place to build confidence. What comes off is a rough rectangle. Rough is fine. Mosaic pieces get set into adhesive and grouted, so a slightly uneven edge disappears into the finished piece.

For a diagonal, take the wheels off the edge and set them into the middle of the tile, lined up along the angle you want.

Cup your hand and squeeze the same way. The break follows the wheels, so placement is the entire trick. Two clean triangles from one square is the most useful cut in mosaic work, and it is the one worth practising on offcuts until it stops feeling like luck.

A curve is not one cut. It is a lot of small ones.

Take little bites around the shape, moving a few millimetres at a time and working your way round the edge. Keep going until the arch looks the way you want it. Nibbling is slower than a single squeeze and it produces a lot of small waste, but by hand it is the only way to get a rounded edge. If the result is jagged, that is what a glass grinder is for.

A full sheet of glass is too big for nippers. Trying anyway wastes glass and risks a break across your hand.

Score the line first with an oil-filled cutter, either a pistol grip or a pencil-style one, then bring in running pliers. Their curved jaw presses down either side of the score and opens it into a clean break across the whole sheet. One pass with the scorer is enough. Going over the same line twice dulls the wheel and gives a worse break.

Most running pliers have a guide mark stamped into the top of the jaw. Line that mark directly over your score, then squeeze steadily rather than snapping at it.

The sheet separates along the line and leaves you strips you can nip down into smaller pieces. Not every pair has the mark, so if yours does not, centre the jaw on the score by eye and keep the pliers square to the line.

Glass dust and slivers build up fast, and they are genuinely dangerous. This is the step people skip and regret.

Sweep the bench with a brush and dustpan into a jar or tin. Sort the usable offcuts by colour while you are there, because a jar of pre-cut tesserae is what makes the next project quick to start. Put the nippers and pliers away rather than leaving them jaw-up where someone reaches in blind.