Although most people are familiar with black mould, mould grows in other colours as well. White mould, also called grey mould, is often undetected for long periods, allowing the colony to grow. To properly clean white mould from unpainted brick, you must remove it from the surface and penetrate the porous structure to kill remaining white mould spores.
Place the flat edge of a plastic-coated spatula against the area of brick with white mould. Hold the spatula any way that feels comfortable to you. Move the spatula in a downward motion to scrape off as much of the white mould from the surface as possible.
Fill a bucket with a solution of four parts water to one part household bleach.
Plunge a scrubber sponge into the bucket to saturate the sponge.
Scrub the area of white mould with the scrubber sponge to remove as much of the mould from the surface as possible. Press the sponge firmly into the brick to penetrate the pores of the brick. Rinse the sponge in the bleach solution often to remove the mould spores from it. Wait two to three days and examine the brick for signs of new white mould growth.
Scrape the area with the spatula if the mould returns and reapply the bleach mixture with the scrub sponge.
Put on a face mask to prevent inhalation of the mould spores during cleaning. In addition, wearing gloves will protect your hands from bleach irritation. If the brick surface is indoors, repair areas of moisture seepage causing the mould growth.
Do not use a pressure washer on brick surfaces, as it can damage the brick and cause the mortar to crumble. Do not use a metal spatula, as it will chip the surface of the brick.