Cleaning monuments, stone and facades with a laser — what conservation publications say

RC-Laser Team · 2 November 2026

Is a laser suitable for cleaning historic facades and stone? The first use in Poland, the risks and the conservator's permit.

First use in Poland: the Tomb of the Unknown Soldier

In 1999, in the quarterly Ochrona Zabytków, Andrzej Koss and Jan Marczak described the cleaning of selected stone elements of the Tomb of the Unknown Soldier in Warsaw with a Q-switched Nd:YAG laser. The authors write that this was the first such use in Poland. Hard, black layers that had built up over several decades were removed. Conclusions: the method is the most effective and the least aggressive, allows contaminants to be removed selectively and is convenient for work on high scaffolding. The available abstract gives neither parameters nor numerical results ^[1].

What is written about the risks

A 2021 article in Renowacje i Zabytki lists specific risks: facing brick may turn grey, sandstone may show visible pitting and wood may scorch. It stresses that most industrial devices on the market work on metal only, that the result depends on the operator and the device, and that holding the laser in one spot for longer risks damaging the surface ^[2]. The same text describes two-dimensional scanners that automatically clean a field of up to about 18×18 cm and limit the operator's influence ^[2].

Wikipedia also lists the use of laser cleaning in the restoration of paintings, sculptures and frescoes ^[3].

How we describe it

What we work on: ceramic and clinker brick, sandstone, limestone, granite, mineral plasters, architectural concrete, stucco detail and metal elements.
What we remove: sulphate deposits, soot, algae, old paint coatings, mortar residue and graffiti.
Test: on historic objects, a test on a small, agreed area is standard, with parameters chosen for the specific deposit.
Conservator: we talk to the conservator before work begins, and documentation from the test usually settles doubts faster than a description of the method.
Permit: for a monument entered in the register, the Polish Act on the Protection and Care of Monuments (Ustawa o ochronie zabytków i opiece nad zabytkami) requires a permit from the voivodeship monument conservator (wojewódzki konserwator zabytków) for conservation, restoration or construction work on the monument (Art. 36(1)(1)) and for other actions that could harm the substance or change the appearance of the monument (point 11). The permit also applies to construction work in the surroundings of the monument (point 2) ^[4]. Whether cleaning a particular facade requires a permit is for the conservator to assess — so it is worth asking before commissioning the work.
What a laser will not do: discolouration that has penetrated deep into porous stone, and rusty streaks from a corroding anchor inside the wall, will remain; in the second case the anchor is repaired first, then the face is cleaned.

Laser versus sandblasting and wet methods

A laser does not abrade the face of brick or the profile of a sculpture and does not wash out joints; nor does it put water into the wall before the frost season or leave streaks on the facade below. Sandblasting is rarely used on non-metallic materials ^[5].

The job

Send us a photo and we will send back a preliminary assessment. We give the final price after inspecting the object on site.

The information on regulations refers to Polish law, is general in nature and is not legal advice. For a specific object, the voivodeship monument conservator (wojewódzki konserwator zabytków) decides.

Sources

Sources as of 2 November 2026.