Journal

Why a Secure Seal goes on the canvas, not the stretcher bar

Published 23 September 2026 — Last updated 23 September 2026 — Build log, by Jason Patten

A Veriroo Secure Seal is a small NFC sticker. A buyer taps it with a phone and sees the record of the piece it belongs to. The obvious question, once you are holding one, is where on the piece it should go.

It belongs on the canvas itself. There are two reasons, and the second one is the one that settled it.

The first reason: read range

NFC reads over a couple of centimetres, and everything between the phone and the chip counts against that. A seal on the canvas itself sits about a millimetre behind the paint, so a phone laid flat on the front of the painting reads it without any trouble. Canvas and paint do not get in the way.

A seal on the wooden stretcher bar is a different story. Now the phone is separated from the chip by the depth of the bar and an air gap, which is usually more than it can manage. So the buyer taps, nothing happens, and they draw one of two conclusions: the piece is not genuine, or our technology does not work. Both are bad, and neither is true.

The second reason: a stretcher is not the work

A stretcher can be replaced. Canvases get re-stretched after damage, or for travel, or because the original bars warped. The canvas is the work. The bars are furniture.

So a proof of authenticity attached to the furniture can be parted from the thing it was proving, with nobody behaving dishonestly at any point. A restorer does a normal job and the proof ends up in a skip.

On the canvas, that cannot happen by accident. Taking the seal off means damaging the work, which is the entire point of putting one there.

What the app tells you

Three places say the same thing, so the guidance does not depend on anyone reading this post:

• When you mark where the seal sits, the hint tells you to put it on the canvas itself rather than the frame or the stretcher bars, and says why: your buyer taps the front, so the seal needs to be directly behind that spot.
• The buyer's sheet says to hold the phone flat against the front of the piece, over the marked spot, and keep it still. Not "hold your phone against the seal", which reads as: go and find the sticker.
• The message you get when a tap fails repeats it, rather than implying the seal is faulty.

None of that is about the seals themselves. The chips, the certificates and the records are the same either way. It is about describing the gesture that actually works.

Why publish this at all

Because the reasoning is the useful part. Anyone can read an instruction that says put it on the canvas. Knowing that it is about read range through wood, and about what happens to a stretcher over thirty years, is what makes the instruction stick.

It is also how I intend to write about the platform generally. When a decision gets made, the reasoning goes here. A platform whose whole argument is that a record should be checkable rather than taken on trust should keep one of its own.