Cleaning old bricks: fine abrasive blasting or sandblasting?

What is the best way to clean old bricks?

After years of use, old bricks may be soiled with soot, atmospheric deposits, paint, moss, cement residues or other contamination. The right cleaning method depends on the brick, the contamination and the condition of the surface.

With historical masonry, do not automatically choose the most powerful method. An overly aggressive treatment can damage the original fired surface or joints, or leave the surface permanently rougher. Always begin with the least intrusive method expected to give a sufficient result.

First establish what is on the brick

Not every type of contamination needs the same treatment. Loose dirt and light deposits require a different approach from multiple paint layers, hard cement residues or heavy soot. It also matters whether you are cleaning an entire facade or preparing loose reclaimed masonry bricks for reuse.

Preferably test a cleaning method on a small, inconspicuous area first. This shows not only whether the dirt is removed, but also how the treatment affects colour, texture and pointing.

Fine abrasive blasting of old bricks

Fine abrasive blasting, known in Dutch as luchtgommen, is a blasting technique that uses relatively low pressure and a fine abrasive medium. It can therefore be applied with more control and less aggression than heavy blasting.

This makes it interesting where retaining the original surface is important. However, the exact pressure, abrasive and distance must still suit the brick and contamination. A gentler technique does not automatically mean damage is impossible.

For more about the technique itself, read our detailed explanation of fine abrasive blasting.

When can fine abrasive blasting be suitable?

Fine abrasive blasting may be considered for light to moderate contamination, certain paint or soot residues, and situations where controlled cleaning is important.

A sample area is especially important for old, relatively soft or vulnerable bricks. The condition of the fired surface and pointing helps determine how much treatment the masonry can withstand.

Sandblasting old bricks

Sandblasting and other more intensive blasting methods treat the surface more forcefully. They can remove stubborn contamination, but carry a greater risk of damaging bricks and joints if applied too aggressively.

On old facades in particular, losing the original fired surface can change the appearance and leave the surface rougher. Consider not only how quickly the facade becomes clean, but also how much original material remains.

If you are considering this method for existing masonry, also read our separate article on sandblasting an old facade.

Fine abrasive blasting or sandblasting: which is better?

There is no single best method for every old brick. In general, the gentlest treatment that achieves the desired result is preferable.

Fine abrasive blasting usually offers more scope for controlled, relatively gentle work. More intensive blasting may be necessary for stubborn contamination on a sufficiently strong substrate, but requires greater caution.

Have the bricks, joints and contamination assessed before treating an entire valuable or historical facade. A sample area often provides far more useful information than choosing solely by the technique’s name.

Can paint and cement residues be removed?

That depends on the type of layer and the substrate. Thin surface contamination differs from old, stubborn paint or cement strongly bonded to the brick.

On loose reclaimed bricks, mortar is often removed not by blasting the visible face but by chipping the old mortar off, known in Dutch as bikken. Old lime and cement residues are removed from the relevant faces so the bricks can be laid again.

Read more about the process in having reclaimed bricks cleaned of mortar.

Cleaning loose reclaimed bricks for reuse

The aim with loose reclaimed bricks differs from facade cleaning. The visible face often does not need to look completely new. Natural colour differences, signs of use and patina determine much of its appearance.

Making the bricks suitable for laying is more important. Old mortar must be removed where necessary and the bricks selected for usability. Overly thorough cosmetic cleaning can remove some of their historical character.

Must a cleaned facade then be impregnated?

Not automatically. Whether impregnation is desirable depends on factors including the condition and porosity of the masonry, moisture exposure and the chosen cleaning method.

It should therefore not be a standard next step after every cleaning job. First establish why the facade absorbs moisture and whether a water-repellent treatment suits that particular construction.

Read more in our article on facade impregnation.

Common mistakes when cleaning old bricks

Starting immediately with high pressure

More pressure does not automatically produce a better result. Aggressive treatment can unnecessarily remove material from an old brick’s surface.

Not preparing a sample area

A small sample shows how the brick, joint and contamination actually respond. It prevents surprises after an entire facade has been treated.

Treating every old brick alike

Handmade, moulded and other historical bricks can differ considerably in hardness, surface and condition. The method must suit the material actually present.

Wanting the facade to look completely new

An old facade does not have to look uniform and new to be clean. Excessive cleaning can remove the colour nuances and weathered character for which historical brickwork is valued.

Preserving the character of old bricks

Good cleaning is not only about removing dirt. It also preserves the properties that make the bricks distinctive. A facade can still show its historical character after cleaning.

The same applies when reclaimed bricks are reused in restoration or new builds. Our projects show how natural differences in colour and texture become part of the final facade.

Clean or replace old bricks?

Where an existing facade is badly damaged, local repairs may be wiser than increasingly intensive cleaning. Missing or unusable bricks can be replaced with suitable reclaimed examples.

Van Dillen Antieke Bouwmaterialen offers a large, changing range of reclaimed masonry bricks in different colours, sizes and production types. This makes it possible to find a close match for existing brickwork during restoration or extension.