Published on 10/16/2026 · by Leandro Caldas, glazier, founder of Routeck and creator of the Arena
How to cut a mirror by hand from a template you can't touch (EP3)
In the third episode of Arena do Vidro I said the challenge was an easier one. The contestants picked one of two shapes and had to cut exactly that shape in mirror. No edging, nothing else. Just the cut. Time: 20 minutes.
The catch: they couldn't touch the template. No laying it on the mirror and tracing around it. They had to measure, transfer the drawing and cut by hand. Within two minutes it was clear there was nothing easy about it.
The problem isn't the cut, it's transferring the drawing
At the judges' table, the read was spot on: the hardest part wouldn't be cutting, it would be getting the drawing onto the mirror. On a curved shape, width and height aren't enough. The problem is the outline, the path the curve takes from one point to the next.
One judge said what he'd do: circles and quadrants to approximate the curve. Split the drawing into sections, find the curves that look like arcs of a circle and build the outline piece by piece. Ten minutes in, neither contestant had the drawing right yet.
The mistakes the judges pointed out
- Not measuring the right points. Natan showed it on Janael's mirror: he needed one measurement here, another there and the most important one, and only then cut the curves. What was extra on one side was missing on the other.
- A flipped drawing. Janael admitted it: he went by the measurements but got the orientation wrong. The shape came out mirrored compared with the template.
- Chipping a straight edge. The sheet already had a straight factory cut. Trying to nibble off a sliver made the good edge crooked and started a run.
- Tapping marks. Tapping to open the score left marks along the edge, the same mistake Vinícius had been pointing out since EP1.
- Breaking out in the wrong order. The mirror closest to the template cracked at break-out: the side cuts were made first and the break ran inward.
The judges' dilemma
The panel's pickiest judge pulled a caliper out of his pocket to measure the gaps. And the dilemma was clear: Rômulo cut closer to the template, with a smoother line that followed the shape. But his mirror cracked. Janael's didn't crack, but his cut was rougher and far from the drawing.
Vinícius gave the verdict: it was hard even to judge. One got close and cracked, the other didn't get close at all. Result: a tie. And he added a message: if they'd used even 10% of what the panel said about handling the cutter and breaking out, the result would have been different.
How to cut a mirror by hand from a template
| Step | What to do | EP3 mistake it prevents |
|---|---|---|
| 1. Measure | Take the overall size and the points where the curve changes | Extra on one side, short on the other |
| 2. Divide | Grid the drawing and approximate curves with circle arcs | An outline with no shape |
| 3. Check orientation | Before scoring, make sure the drawing isn't mirrored | A flipped shape |
| 4. Use the straight edge | Keep the sheet's factory edge wherever the template is straight | A good edge turned crooked |
| 5. Break out in order | Open the score with taps from below, not with the cutter, and break out before the waste cuts | A run into the piece and a crack |
On a machine, the same shape takes a minute
While they struggled, I told the truth: with the Router Glass, I cut mirror into any shape. A mirror like that would take me about a minute, cutting on my own. In the Arena I made it a hand challenge precisely to see who's good without a machine. In your shop, the math is different.
- What was the EP3 challenge in Arena do Vidro?
- Hand-cut, in 20 minutes, one of two shapes exactly matching a template, without laying the template on the mirror. No edging, just cutting.
- How do you transfer a curved drawing to mirror without tracing?
- Measure the points where the curve changes and approximate the outline with quadrants and circle arcs, as one judge suggested. And check that the drawing isn't mirrored before you score.
- Who won EP3?
- Nobody: it was a tie. Rômulo came closest to the template, but his mirror cracked at break-out; Janael's didn't crack, but it was far from the drawing.
The full EP3 is at the top of this post (audio in Portuguese). If you cut mirror by hand better than these two, applications for the next Arena season are open here on the site.
Full episode 3 · How to break out a mirror without chipping · How to cut a mirror into shapes