Sandblast vinyl on mirrors: wet application or dry strips?

In Arena do Vidro EP1, after breaking out the Hello Kitty mirror, each contestant had to apply vinyl so they could then cut the band for sandblasting. It looks like the easiest step of the challenge. It wasn't. They applied the vinyl in completely different ways, and each explained why.

Every glazier who starts sandblasting has this question: does sandblast stencil go on wet or dry? Whole roll or strips? In this post I show what each of them did and what matters when you choose.

Janael: soapy water, even without the soap

Janael finished his break-out first and chose to edge before anything else. When he got to the vinyl, he had a surprise. In his shop he uses a lot of water with dish soap. In the Arena there was only water. He said that when he saw there was only water he panicked a little, but water still helps.

His reasoning is the same one many people who sandblast give: laying film dry on a mirror is a real pain to get smooth. With the mirror wet, the vinyl doesn't grab right away. You can adjust it, pull it, stretch it and push out bubbles before it sets. He said himself that water alone isn't ideal, soapy water is. But the water did the job.

▶

Rômulo: dry, in strips

Rômulo took the whole roll and tried to lay the vinyl out in one piece over the mirror. On the first try he saw it wasn't going to work. He noticed something else too: the vinyl's weight was different from what he uses, and that changed how the material behaved.

So he went back to his shop method: cutting the vinyl into strips. For him it's easier when working alone; a big sheet like that would need one or two more people to help. Once the strips were cut, he applied them easily. He also made it clear water isn't part of his routine, so much so that he never even noticed his rival was using it.

The two methods side by side

How to choose in your shop

• Working alone on a large mirror: strips, like Rômulo. Stretching a whole roll with no helper means bubbles and wrinkles.
• Need a smooth finish and have time to let it set: water with a few drops of dish soap, like Janael does in his shop.
• Switched vinyl brands: test first. Rômulo felt the difference in weight right away. New material behaves differently.
• With strips, watch the seams: where one strip meets the next, there can't be a gap.
• With water, be patient: squeegee the water out from underneath and let the vinyl set before cutting the design.

In the end both methods worked. What made the difference was that each of them knew his own way of working and the material. And the hardest part came next: cutting the design by hand was the step that made both of them sweat the most. But that's for the next clip.

Should sandblast stencil vinyl go on wet or dry?

Both work. In the Arena, Janael applied it with water (in his shop he uses water with dish soap) and Rômulo applied it dry, in strips. It depends on whether you have help, the size of the piece and the material.

Why apply the vinyl in strips?

Because one person alone can apply it without a helper. Rômulo explained that a big sheet would need more people to help.

Why add soap to the water?

According to Janael, water alone helps, but soapy water is ideal. The soap lets the vinyl slide over the mirror until you've positioned it and pushed out the bubbles.

The clip with this part is at the top of the post, and the full EP1 is on the episode page. If you've mastered vinyl and sandblasting and think you'd do better, applications for the next Arena season are open here on the site.

Full episode 1 · How to break out a mirror without chipping · Jateck: the sandblaster both contestants used in EP1

Episode 1