The question comes up in almost every enquiry we get, and it deserves a straight answer rather than a reassuring one. A memorial is supposed to outlast the person who commissioned it. A plaque that stops scanning after three winters is not a memorial. It is litter with sentimental value.
So: what does a British graveyard actually do to a QR code, and what survives it?
What the weather is really doing
Four things wear out an outdoor plaque, and only one of them is rain.
Ultraviolet light. The main killer of printed and vinyl codes. UV breaks down the pigments in ink, and it does not need sunshine to do it. Black fades to grey, greys drift towards the background tone, and the contrast the camera relies on quietly disappears. A code can look perfectly present to your eye and be unreadable to a phone.
Freeze and thaw. The specifically British problem. Water gets into a seam, a fixing hole, or the gap between a laminate and its backing. It freezes overnight, expands, and levers the layers apart. Repeat forty times a winter. This is why laminated and layered plaques delaminate here in a way they do not in drier climates, and why a single solid piece of metal is a fundamentally better design than a sandwich.
Biological growth. Lichen, algae and moss, which love damp shaded stone and will happily colonise a plaque fixed to it. This is the most common real-world cause of a scan failing, and the good news is that it is completely reversible with a wipe.
Salt and pollution. Coastal air and roadside grit will pit ordinary steel. This is a genuine material-selection issue rather than a maintenance one: 304 stainless is fine inland and will develop rust freckles within sight of the sea, where 316 grade is the right specification.
Materials, ranked honestly
Printed vinyl or paper under laminate. Avoid for anything outdoors. Cheap, looks fine on arrival, and typically loses usable contrast within two to five years. Fine for an order of service. Not fine for a graveside.
Anodised aluminium, laser-marked. Good. The laser burns through the anodised layer to the bright metal beneath, so the code is a physical feature of the surface rather than a coating on it. Light, will not rust, holds contrast well. Softer than steel, so it scratches more easily.
Stainless steel, laser-marked or etched. The best all-round choice, and what we use. The mark is part of the metal. There is no layer to peel, fade or delaminate, because there is no layer. Grade matters: 316 for coastal, 304 elsewhere.
Fired ceramic or vitreous enamel. Genuinely excellent optically and effectively UV-proof, which is why Victorian enamel signs still read perfectly. The weakness is brittleness. It survives a century of weather and does not survive one strimmer.
Engraved brass. Traditional and handsome, and it will last indefinitely as a physical object. The subtlety is that brass patinates, and as it darkens the contrast between the engraved code and the surrounding metal narrows. It stays scannable, but it benefits from an occasional polish in a way steel does not.
The thing that actually keeps a code readable
Here is the part most suppliers never mention, and it matters more than the material.
Every QR code carries built-in error correction, using a mathematical scheme that stores the data redundantly. There are four levels, and the level is chosen when the code is generated:
- Level L tolerates roughly 7% of the code being damaged or obscured
- Level M tolerates roughly 15%
- Level Q tolerates roughly 25%
- Level H tolerates roughly 30%
A code generated at level H will still scan with nearly a third of its surface covered in lichen, scratched by grit, or obscured by a water droplet. A code generated at level L will fail at the first serious blemish. The two codes look almost identical to you. They behave completely differently after five winters on a north-facing headstone.
The trade-off is density: higher error correction means more modules in the same area, which means each module is physically smaller. This is precisely why plaque size and error correction have to be chosen together, and why a very small plaque carrying a very long web address is a bad combination. Short addresses make for sparser, more robust codes. It is one of the reasons a well-designed memorial code points at a short link rather than a long one.
Glare, angle and contrast
A phone camera needs to see light and dark areas distinctly. Two practical consequences follow.
Polished mirror finishes are a poor choice outdoors, because in direct sun the whole surface returns one sheet of white light and the camera sees no pattern at all. A brushed or matte surface scatters that light and keeps the pattern visible. This is a real reason to prefer brushed steel or matte black over a high polish, quite apart from taste.
Fitting angle matters too. A plaque set flat on a horizontal surface collects standing water, grit and leaf litter, and catches the sky as glare. A plaque on a vertical or gently raked face sheds water and sits in more even light. If you have a choice of faces on a memorial, the vertical one is better.
Fixing
Adhesive fixing, using a structural exterior adhesive, is the standard method on stone and is genuinely durable when the surface is clean, dry and above about five degrees at the time of fitting. Cold, damp fitting is where adhesive failures come from, which makes a January installation a worse idea than a May one.
Mechanical fixing, with pins or screws into drilled holes, is stronger but introduces holes, and holes let in water that then freezes. On stone it also usually requires a mason, and in most council cemeteries it requires one anyway.
On a wooden bench, screws are the right answer. On stone, well-executed adhesive is generally better than badly-executed mechanical fixing.
Maintenance, which is almost none
Once a year, when you are there anyway: warm water, a soft cloth, wipe it. That is the whole regime. It removes the lichen and algae that cause the overwhelming majority of scan failures.
Do not use wire wool, bleach, or a pressure washer. Wire wool leaves iron particles that rust and stain. Bleach and acidic cleaners damage the surrounding stone, which will annoy the burial authority considerably more than it annoys you. A pressure washer can drive water behind an adhesive bond.
If a code will not scan, try this order before assuming it has failed: wipe it, shade it with your hand to kill glare, move to about arm's length, and clean your phone's camera lens. In our experience one of those four fixes it nearly every time.
How to test whether a supplier is serious
Ask them two questions. What material and grade is it, and what error correction level is the code generated at?
A supplier who can answer both immediately has thought about the twenty-year problem. A supplier who answers the first and not the second has bought plaques wholesale and is guessing. It is a short conversation and it is remarkably revealing.
Our own plaques are marked stainless steel in brushed, matte black and antique brass, at 50mm and 80mm, with the code and the size chosen together so the finished plaque scans reliably at the distance it will actually be read from.