Journal

Where the seal goes, and why we changed our mind

23 September 2026 — Build log

A Veriroo Secure Seal is a small NFC sticker that a buyer taps with a phone to confirm a piece is the one its record describes. Until this week, our guidance on where to put one was vague: somewhere on the back. That turns out to be two different pieces of advice, and only one of them works.

The physics bit, briefly

NFC reads at a range of a couple of centimetres, and the distance is measured through whatever sits between the phone and the chip. Stick a seal on the raw canvas itself and the chip is roughly a millimetre behind the paint, so a phone held flat against the front of the painting reads it easily. Fabric and paint do not block it.

Stick the same seal on the wooden stretcher bar and the situation changes. Now the phone on the front is separated by the depth of the bar plus an air gap, which is often outside the range entirely. The buyer taps, nothing happens, and they conclude the piece is fake or the technology does not work.

The part that matters more than the physics

There is a second reason, and it is the one that decided it. A stretcher can be replaced. Canvases get re-stretched after damage, or when a work travels, or simply because the original bars warped. The canvas is the work; the frame around it is furniture. A proof of authenticity attached to the furniture can be separated from the thing it was proving without anyone acting dishonestly.

Put the seal on the canvas and that cannot happen quietly. Removing it means damaging the work, which is exactly the property a tamper evident seal is supposed to have.

What changed in the app

Three small things, all shipped this week:

• When an artist marks where the seal sits, the hint now says to put it on the canvas itself, not the frame or the stretcher bars, and explains why: a buyer taps the front, and the seal has to be directly behind that spot.
• The buyer’s sheet used to say “hold your phone against the seal”, which reads as an instruction to find the sticker first. It now says to hold the phone flat against the front of the piece, over the marked spot, and keep it still.
• The failure message says the same thing, rather than suggesting the seal is at fault.

Nothing about the seals themselves changed. The chips, the certificates and the records are the same. What changed is that the instructions now describe the gesture that actually works.

Why write this down

Because the wrong version was live for a while, and some seals are already on stretcher bars. If yours is, it will still read when tapped directly on the back at that spot; it just will not read from the front. Move it on the next piece rather than digging at the current one.

We would rather publish the correction than quietly change the copy. A platform whose entire argument is that records should be checkable does not get to be shy about its own.