Cutting a sandblast stencil: by hand or by laser?

In Arena do Vidro EP1, the Hello Kitty mirror came already cut on the Router Glass. The same machine that cuts the mirror also laser-cuts the vinyl. But in this challenge I took that help away: the sandblast stencil had to be cut by hand.

It was the step that made both contestants sweat the most. And it's a step plenty of glass shops still do every day with a utility knife. In this post I show what happened, how each man got by, and what changes when stencil cutting moves from your hand to a machine.

Without his shop tools: a ruler and a razor blade

One contestant summed up the problem: he already had an idea of what to do, but he didn't have the same tools as in his shop. He had to look at the board and make do. He grabbed a ruler and ran a razor blade along it. It worked, but it left marks.

On the straight lines he managed to hold his hand steady to mark and then peel the film. The problem was the Hello Kitty bow. No ruler could help there, and there was no template. He had to draw it calmly and peel the film by hand. But it worked out.

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Rômulo's improvised template

For Rômulo, this was the worst part of the episode: the difficulty went way up. He knows hand cutting isn't his strength, so in his shop he uses a set of templates he made himself, mostly for organic shapes with tight curves like that mirror had.

In the Arena he tried it by hand, saw it would come out terrible and changed tactics: with what was on the bench, he built a rough copy of his template. That's how he managed the cut. In his words, if it had been by hand alone, it wouldn't even have come out the way it did.

What hand cutting cost them

At judging time, the panel compared every detail with the model. The harshest line came from Rui: the only thing that matched the model was the cut, and the machine had made it. Outline, width of the blasted band, the button: whatever depended on the hand came out different. It proves that, in sandblasting, the final design is the stencil cut. If the stencil is off, the blast is off.

If you still cut stencils by hand

• Make templates for the designs you repeat, like Rômulo does. A template turns skill into a process.
• Use a solid ruler on straight lines and a sharp blade. A dull blade drags the film and makes you push harder.
• Watch your pressure: the goal is to cut only the film. In the Arena, the blade left marks.
• Draw the details calmly before cutting. The bow is where both men struggled most.
• As volume grows, add up the time you spend with the knife. That's the time a machine gives back.

Can you cut a sandblast stencil by hand?

Yes, and many glass shops do. In the Arena, both contestants cut by hand with a ruler, a razor blade and an improvised template. Straight lines come out fine; tight curves and details, like the Hello Kitty bow, are where the hand struggles.

What is a stencil-cutting template?

A rigid guide the glazier makes to steer the blade around curves he repeats. Rômulo keeps several in his shop and, in the Arena, built a copy on the spot to cut the bow.

Does the Router Glass cut vinyl?

Yes. In EP1 it was mentioned that the machine cuts mirror and also laser-cuts the vinyl. In this challenge, on purpose, the contestants had to cut it by hand.

The clip with this part is at the top of the post, and the full EP1 is on the episode page. If you cut stencils by hand better than these two, applications for the next Arena season are open here on the site.

Full episode 1 · Sandblast vinyl on mirrors: wet or in strips? · Sandblasting without a cabinet: the Jateck

Episode 1