Scoring and breaking glass
Scoring and Cutting - Uncategorized

Stained glass scoring and breaking


Scoring and breaking stained glass is a crucial step in the process of creating a stained glass panel. Precise cuts are essential for achieving a smooth, seamless fit and for creating a professional-looking piece. In this blog post, we will go over the tools and techniques needed for scoring and breaking stained glass, as well as offer tips for achieving precise cuts.

scoring and breaking glass

Whether you are a beginner or an experienced stained glass artist, there is always room to improve your skills in scoring and breaking. By following the steps and tips outlined here, you can create beautiful and accurate cuts in your stained glass projects.

To begin, it’s important to clarify what we mean by “scoring”. This is the initial step in the process of cutting glass. This is done using a specialized tool called a glass cutter, which has a small, sharp wheel that glides over the surface of the glass.

Scoring the glass involves making a thin, continuous scratch on the surface of the glass, extending from one edge to the other. A well-done score should look like a thin line on the glass, without any breaks or gaps.

To achieve a clean score, it’s important to use a steady, consistent motion, applying only light pressure. Applying too much pressure can actually result in a poor break.

Tools needed for scoring and breaking stained glass:

cutting tools for scoring and breaking glass

Glass cutter

A glass cutter is a hand-held tool that is used to score the surface of the glass. It consists of a handle with a small wheel or diamond-tipped blade on one end. To use a glass cutter, you simply place the blade on the surface of the glass and apply pressure while running it along the desired cutting line.

This will create a shallow groove in the glass, which can then be used as a guide for breaking the glass along the scored line. Many companies sell various styles of cutters and pliers. If you need both, a set like this one (link) fits the bill nicely.

Cutting oil

Cutting oil is a lubricant that, when applied to the cutter wheel, reduces friction and heat during the cutting process. The use of cutting oil will prolong the life of the cutting tool and improve the accuracy and precision of the cut.

It also helps prevent the glass from cracking or chipping during the cutting process. When using cutting oil, follow the manufacturer’s instructions and use it in a well-ventilated area, as it can produce harmful fumes

Running pliers

Running pliers for scoring and breaking glass

Once you have scored the glass with your cutting tool, you will need another tool to actually break the glass along the scored line. Running pliers are my top choice for getting a nice clean break exactly where you want it. Similar to regular pliers, they have longer handles and are designed to apply pressure directly along the scored line.

Running pliers have a curved jaw that allows for more control when making long or more difficult breaks. Line up the score with the indicator line on the upper jaw and gently clamp down on the glass for a clean break along the scored line. This allows you to pinpoint the pressure and break the glass more easily.

Grozing (or grozier) pliers

These pliers are used for removing small cutouts, for trimming smaller bits after a larger cut, or removing an inside cut or corner. Grozing pliers are used differently than running pliers, as the Grozier pliers flat tip is butted against the score line, rather than the opposite for running pliers.

Grozing pliers

The most efficient method to remove a small section of glass (as pictured) is to grip tightly and pull it straight out from the glass, rather than rotating the pliers up or down. This works surprisingly well.

Safety glasses and gloves

Working with glass can be dangerous, so it is important to protect yourself by wearing safety glasses and gloves. Safety glasses will protect your eyes from flying shards of glass, and gloves will protect your hands from cuts and abrasions. It is also a good idea to work on a stable, flat surface and to clear away any clutter that could potentially trip you or get in the way.

Scoring and breaking stained glass can seem intimidating at first, but with the right tools and techniques, it’s actually a fairly simple process.

Scoring and breaking stained glass step-by-step

Lay out the glass pieces on a clean flat surface. This will give you a clear view of where each piece needs to be cut, and will help you to avoid accidentally cutting the wrong piece.

Stained Glass Cutting Tools, Tips & Tricks

Use a glass cutter to score a line on each piece of glass where it needs to be cut. To do this, hold the cutter like a pen, with your thumb and index finger on the top and bottom of the handle.

Place the wheel of the cutter against the glass, and apply gentle pressure as you trace along the line you want to cut. Make sure to keep your hand steady and move the cutter in a straight line.

Line up the center of the running pliers with the scored line. Use running pliers that have rubber covers on the jaws, as rough jaws can damage the glass. To break the glass, squeeze the jaws closed over the glass until you hear a crack and feel the glass release along the scored line.

If you are breaking a long scored line, and you hear the glass crack but it does not release, use the running pliers in the same fashion at the other end of the score. Clean up any excess glass and smooth out the edges with a grinder (optional). Once you’ve broken all of the glass pieces, you’ll want to clean up any excess shards or stray bits of glass.

Here is another general tutorial on cutting glass to have a look at (link).

A small broom and dustpan work well for this task. If you want to smooth out the edges of the glass pieces, you can use a glass grinder. Simply place the glass piece on the grinder and run it along the edge until it’s smooth.

Tips for successfully scoring and cutting stained glass

Grinding glass

If you are very new to cutting glass, it helps to practice cutting and breaking on some old, discarded window glass. Hone your skills on throwaway glass and save your money for the good stuff.

Make sure that the cutting surface you are using is flat and completely free of any cutoff bits, shards, or debris of any kind. Your sheet glass is very vulnerable to surface variations and will crack easily.

Always start by cleaning the glass with soap and water or a glass cleaner. This will help to ensure consistent contact between the cutter wheel and the glass.

Make sure you have good lighting in your workspace to help you see clearly and avoid shadows. I strung these lights up in my basement – Wow, what a difference! (link)

Use cutting lubricant. Some cutters have a built in reservoir, others can be oiled periodically between cuts.

Choose a glass cutter that is comfortable for you. When scoring, always work with the smooth side of textured glass to maintain consistent contact with the cutter wheel.

Take extra time to carefully trace and cut out your template patterns. This ensures accuracy when fitting glass pieces.

It can be difficult to remove narrow slivers of glass. Therefore, it’s best to leave a bit of space between the edge of the glass and your tracing.

Lastly, use a steady hand and even pressure when scoring the glass.

breaking scored glass


The importance of precise cuts in the creation of a successful stained glass panel cannot be overstated. Take the time to carefully score and break your glass pieces to ensure a clean, accurate fit.

This can be achieved through a combination of proper technique and practice. And remember, practice really does make perfect! With time and effort, you’ll be able to create beautiful stained glass pieces with precision and confidence.

Thanks for visiting!  Don’t miss this post on painting stained glass.