The most common brick stains and blemishes are effloresces and smoke stains. Effloresces stains can look white and powdery. If you notice a dark stain around your chimney for example, most likely this could be a smoke stain. Removing these stains can be used with muriatic acid, diluted 1-10, but for no longer than a few minutes. After applying the diluted muriatic acid for a few minutes, wash off with water using a garden hose.
You may need to repeat this process a few times, but you’ll want to wait the proper duration between each session. It is important to know that when you are trying to remove mortar stains that have colour additive your muriatic acid, must be diluted 1-100. If the stains are fussy, don’t hesitate to scrub it with a wire brush (stiff fibre brush) in the process of stain elimination. Always wear safety gear when doing so as this chemical can cause permanent damage to the eyes and skin. Also, always add acid to water, never water to acid. Below are 3 different masonry materials and what products to use when trying to remove stains and blemishes.
Removing common stains from different masonry materials:
Brick and concrete: muriatic acid (diluted)
Wash slate, bluestone and granite: laundry detergent
Limestone and sandstone: clean water and scrub brush