Getting a QR code engraved onto stone so it still scans in twenty years
Getting a QR code engraved onto stone so it still scans in twenty years
- Open source
- No sign-up
- No watermark
- Free API + MCP
- In the MCP registry
The stone is the variable, so proof on the stone
Two blocks of the same granite from the same quarry can engrave differently, and polished black granite behaves nothing like flamed grey. Every rule on this page is a starting position; the scan test on the actual material is the rule that counts. Ask the mason for a proof cut on an offcut of the same stone, or on the least visible corner of the base, before the design is committed.
What each cutting method does to a code
A QR code is a grid of squares, and every cutting method has a smallest mark it can make cleanly. If the squares in the code approach that mark, adjacent modules run into each other and the code stops decoding, even though it looks fine to the eye at arm's length. The practical consequence: the bigger the code and the shorter the destination it encodes, the more room each module has, and the more forgiving every method becomes. Keep the destination as short as it can honestly be, then size the code up from there.
| Method | How it treats a code | What to ask for |
|---|---|---|
| Laser engraving | The finest detail of the common methods; a clean edge on most granites at small module sizes | A test cut first: some dark granites mark pale and low-contrast, which changes the infill decision |
| Sandblasting | Coarser than laser; the blast undercuts edges and rounds small features | Larger code, fewer modules, deeper blast; keep the panel around the code clear of fine lettering |
| Hand etching | Skill-dependent detail; a good letter-cutter produces clean squares but slowly | Discuss module size openly; an experienced cutter will say plainly how small they will go |
| Cast bronze | The code is part of the casting, so edges soften in the sand and the patina develops over years | Recessed squares, generous module size, and a deep enough relief that patina in the recesses still reads darker |
Depth and infill: one decision, not two
A scanner reads contrast, not depth. A shallow cut in a mid-grey stone can have almost no contrast from a metre away in flat light, which is the light a cemetery visitor usually has. Depth matters for longevity, for keeping weathering and lichen from filling the marks, and for raking light across a polished face, but depth alone does not make a grey-on-grey code scan. Where the stone cannot give you contrast by itself, infill does: a lithographic black or a stone-safe enamel painted into the cut, wiped off the face. Ask for the infill to sit below the surface, not proud of it, because a filled code that stands slightly proud collects wax, polish and fingers, and loses its contrast back again within a season or two.
Placement on the stone: leave the quiet zone alone
Every QR code needs a clear margin around all four sides, roughly the width of four of its squares, with nothing cut into it: no border, no lettering, no carved rose. Headstone layouts are dense by nature, with inscriptions running close to panel edges, so the quiet zone is the first thing that gets squeezed when the design tightens. Give the mason the code and the margin as one block, sized so the margin travels with it, and keep it clear of the lettering panel: a border line separating inscription from panel tends to get drawn right up to whatever is nearest, and if that is the code, it is dead. On a south-facing polished granite in direct sun, also think about glare: a glossy face can turn into a mirror at the hour people actually visit, which is an argument for a matte panel, an infilled code, or a position out of the afternoon reflection.
The proofing sequence, in order
- 1
Paper proof at final size
Print the actual file at the final millimetre size and scan it. This clears the file and the encoded destination before stone is involved.
- 2
Cut one on the real stone
An offcut of the same material, same finish, same depth and infill as the finished piece.
- 3
Scan in flat grey daylight
Overcast conditions, not direct sun: this is the honest test of contrast without glare helping you.
- 4
Scan in raking light
Low sun across a polished face can wipe a shallow cut out entirely. If it fails here, deepen or infill.
- 5
Wet it and scan again
Rain is when people stand under trees reading plaques. Water changes the surface contrast; know which side of that you are on.
The years afterwards: cleaning without killing the code
A code on stone will spend its life growing things. Lichen and moss sit in the cuts and, at level H error correction, the code usually keeps working through a fair amount of it. What shortens its life is aggressive cleaning: wire brushes, acids and pressure washers strip soft infill, round cut edges and can delaminate polished faces. The cleaning guidance for a coded memorial is the same as for any memorial stone, plus one line: soft brush, water, and if the code is infilled, expect the infill to want topping up every few years, which is a five-minute job for whoever maintains the stone. That line belongs in the care sheet a mason or memorial company hands the family, because in year six nobody else will remember it.