If the yellowish haze appears to be uneven and is on both the masonry and the mortar joints, you likely have acid burn.
Acid burn can be the result of cleaning masonry with muriatic acid, inadequate pre-wetting, or incomplete rinsing when cleaning with an acid-based cleaner. In these instances, acid and/or impurities in the acidic cleaner are rapidly absorbed by the porous masonry and cannot be thoroughly rinsed. The acid and/or impurities attack the masonry and mortar, and salts (insoluble and soluble) are mobilized within the wall assembly. As the moisture evaporates, the mobilized salts are drawn to the face of the masonry and deposited. This process results in an uneven, yellow or gold discoloration on the face of the masonry and mortar joints. In addition to the uneven discoloration, acid burn can also result in severe etching. While the discoloration may be reduced, the etching cannot be reversed.
See the FAQ "How to Remove Acid Burn" for specific cleaner recommendations.
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