How to Lighten Mortar Colors

Many factors influence the brightness of mortar when it is mixed: the color and age of the cement, the color of the sand used and even the amount of water used in the mixture. But there are few products marketed to consumers to lighten mortar after it has set. Luckily, oxalic acid, a product often used to remove stains from wood, can be used to brighten mortar.

Oxalic acid
Plastic mixing container
Wooden stirring dowel
Gloves
Water
Borax

Instructions

- 1
  Purchase oxalic acid, borax, a wooden mixing dowel, plastic paintbrush and a plastic container at a local hardware store.
- 2
  Mix the oxalic acid in the plastic container with water until it forms a thick paste.
- 3
  Apply the paste quickly and thoroughly to the mortar with the brush. The paste should have an abrasive cleaning effect on the bricks, and will not harm them if applied there as well.
- 4
  Allow the paste to cure for thirty minutes to an hour.
- 5
  Apply borax over the paste; this will nullify the active ingredient in the acid, allowing you to handle it if necessary.
- 6
  Wash the paste and borax mixture off of the bricks and allow the mortar to dry.

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