Floor mirror: what the final's rule demands from the frame

A floor mirror looks like the simplest thing in the world: a big mirror, a frame, done, it stands up. At the Arena do Vidro final we found out it is not. The challenge's rule fit in one sentence, "metal frame and it has to stand up", and that very sentence is what separated the one who had structure from the one who only had a frame.

I sat at the judges' bench the whole time, so this post is what I saw up close: what the rule really demanded from the structure, where it almost knocked both finalists down, and what each one did to keep the mirror standing within one hour.

The rule was short, the demand was big

"Metal frame and it has to stand up" has two parts, and the second one carries the weight. A full-length mirror is heavy and tall; for it to stand on its own, with no wall and nobody holding it, the frame needs a foot, a base that takes the weight and keeps the whole thing from tipping forward or back. In other words: the challenge was not asking for a pretty frame around the mirror, it was asking for a structure that works.

That difference is what we discussed at the bench while the two were cutting. One of the judges summed it up: if he just puts a flat bar behind it for support, it will not work. Doing only the bar with the frame, the mirror will not stand.

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Structure first, frame second

The order that works for a floor mirror is this: first the part that carries the weight, then the part that shows. Flat bar fools you. It bends easily, makes a nice outline, but it is limp: when you stand the mirror up, it gives. What holds is square tube, making the frame and the foot. Flat bar comes in only as support, not as the skeleton. I already wrote a whole post about flat bar versus square tube, so here is just the summary: tube is the structure, flat bar goes along.

Welding pulls, and the cut has to know it

The detail that caught my attention most at the final was Rômulo's. He cut the tube to the right size, and when he welded it, the weld pulled the metal: the frame went out of size and he had to cut and weld again. That is physics, not a cutting mistake. The heat of the weld shrinks the joint and the frame closes up a little. Anyone who makes metal frames every day already knows this and leaves a few millimeters extra for the weld to eat. In a one-hour challenge, every piece redone is time that does not come back.

Planning the weld is worth more than knowing how to weld

Janael went the other way. Welding is his weak spot, and he knew it. So he brought Rui, a metalworker with ten years of welding, and showed up with the design ready. Rui welded the frame and the foot in under ten minutes and said the line that sums up the strategy: "the design was already done, I just executed it". He did not have to think, only join what was already decided. For a floor mirror that is worth a lot: whoever defines the structure before turning on the welder spends less time and makes fewer mistakes.

Big or small, the mirror has to stand

Rômulo did consider a way out: a smaller mirror standing on a tripod. It met the rule, metal frame and standing, with less weight to hold. In the end he saw the full-length mirror on the other side and copied the size, something we already discussed in the post about reading the rules before cutting. His own conclusion after the challenge is the one I leave here: the mirror has to stand in a frame, no matter if it is pretty or ugly.

• Read the whole rule: "stand up" demands a foot and a base, not just an outline.
• Square tube makes the frame and the foot; flat bar only goes along.
• Leave a few extra millimeters when cutting the metal: the weld pulls.
• Decide the structure before welding; the welder only executes.
• If the size is free, smaller and standing beats big and tipping over.

What did the Arena do Vidro final's rule require?

A metal frame and a mirror that stands on its own, in one hour. The mirror size was free.

Why doesn't flat bar hold a floor mirror?

It bends easily, which makes it look practical, but standing up it gives. It works as support and finish on top of a square tube structure, not as the structure.

Why did the frame go out of size after welding?

Welding heats and shrinks the joint, pulling the metal. That is why you cut a few millimeters long and check the size after welding.

The full final episode is on the site, with the whole challenge from the rule to the result. If you want to see how the mirror was cut before it went into the frame, the mirror cutting machine guide on the Routeck site shows the Router Glass we use at the Arena.

Full episode 4: the final · Flat bar mirror frame: why flat bar fools you on a standing mirror · Full-length or small mirror: read the rules first · Guide: mirror cutting machine

Episode 4