How to Cut Straight Lines in Stained Glass Cleanly

Straight cuts look like the easier version of curved cuts, and in some ways they are, but they come with their own specific technique worth getting right, especially since most beginner patterns include a mix of both.

Why Straight Cuts Still Go Wrong

The most common mistake on a straight line isn't the score itself, it's the break. A straight score with an uneven or off-center break can wander slightly off-line even when the score was clean, especially on longer cuts. Straight lines also tempt beginners to rush, since they feel simpler, which is exactly when inconsistent pressure creeps in.

Scoring Technique

Use a straightedge as a guide for longer lines rather than freehanding, this keeps your pressure and direction consistent in a way that's harder to maintain by eye alone. Score in a single, continuous pass from edge to edge, the same principle that applies to curves: stopping and restarting partway creates a weak point that can cause an uneven break.

Breaking the Line

For straight cuts, running pliers positioned directly on the score line, centered along its length, give you the most control. Apply even pressure and let the glass separate along the score rather than twisting or forcing it. On longer straight cuts, breaking from the center outward in two motions can give a cleaner result than trying to snap the entire length at once.

When Straight Cuts Matter Most

Straight lines often form the outer border of a pattern piece or separate large background sections, meaning any wander in the line is more visible than it would be on an interior curve surrounded by other pieces. Taking a little extra care on border and background cuts pays off more visibly in the finished piece than the same care on a small interior piece.

Where to Start

Most beginner patterns mix a handful of straight cuts with gentle curves, giving you a chance to practice both techniques on pieces forgiving enough that small imperfections won't show.