Building with brick or stone usually requires the inclusion of mortar as a binding agent between the materials. Made from Portland cement, most mortar appears dull grey in colour, but many builders tint the material slightly to go along with the stones or brick used. Colouring mortar can be a tricky process, however, and sometimes when the mortar dries it's not quite the colour intended. When this occurs, there's no need to remove and replace the material. With a brick dye, you can correct the mortar colouring, replacing the existing colour with the one you desire.
Wear protective gear throughout the etching and tinting process, including a respirator, safety goggles and rubber gloves.
Prepare the mortar for the brick dye by etching the mortar surface slightly to roughen the texture and open the pores in the material. Fill a pump-up sprayer with a biodegradable masonry etching solution. Press the pump up and down a few times to add air pressure to the sprayer, and then point the nozzle directly at the masonry and mortar surface from about 8 inches away. Press the trigger on the sprayer to start the flow of etching solution and spray the entire surface with a light covering.
Wait about 30 minutes for the etching solution to penetrate the surface, and then wash it off with a power washer. Wait two to three hours after rinsing for the mortar to dry out before changing its colour.
Mix a batch of brick tint following the manufacturer's directions using a wooden stir stick. The brick tint is available in a small number of colours, but you can mix tints to create the colour you wish to apply to the mortar. Test the colouring on a section of mortar not easily seen, using a small paintbrush, to ensure the proper colouring before applying it to the entire surface.
Use a paintbrush to brush the mortar with the brick tint. Apply a light coating of the tint to the mortar lines, taking care not to drip the tint onto the masonry surrounding the lines. The first layer will only give you a translucent coating, tinting the mortar slightly. Apply multiple coats of the tint to deepen the colouring until you achieve the correct colour of the mortar that you're looking for. Wait four hours between each coat to allow the tint to dry to note the true colour of the mortar after each coat's application. If you drip tint onto the masonry, remove it immediately with a damp sponge to keep the tint from penetrating into the stone. Wait 24 hours after applying the final coat before touching the mortar.