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porous brick and mortar joints and leave behind salts. NPS recommends spot cleaning rather than cleaning entire surfaces with commercial cleaners, if cleaning is indeed necessary. The GSA rule of thumb is to achieve 85% clean rather than 100% clean. GSA specifications generally call for a very mild blend of buffered ingredients and wetting agents (3% solution or 1 part concentrate to 16 parts water). No metal buckets or bowls. Products containing muriatic acid should not be used. Hydrofluoric acid (HF) will not leave behind salts and it found in masonry restoration cleaners, but would etch limestone. Copious amounts of water should be used to dilute acidic cleaners and protect limestone from etching. Natural fiber brushes and low water pressure (max 300 psi) should be used during cleaning. NPS and GSA recommend hand trowling'mortar joints, but the specifications seem to adequately provides incentives to diligently grind mortar joints without nicking bricks and finishing the joints by hand. NPS repointing guidelines specify the use of lime mortar, which the submitted specifications follow closely. Staff recommends approval the specifications submitted by Forum Architecture and the School Corporation for Monroe School with the following additions and amendments: 04500 — Masonry Restoration 1.1 General D. Gently wash all surfaces and clean with commercial cleaner where needed. 2.3 Sealants Provide a non -silicone based sealant as silicone based sealants can retain water within the masonry. A sealant would probably not be necessary if a low-pressure wash were used without commercial cleaners. 2.4 Cleaners A. #600 Sure Klean detergent should not for this project. Appropriate cleaners would be Sure Klean Restoration Cleaner, Sure Klean VanaTol, 101 G Granite, Terra Cotta, Brick Cleaner, or other similar products. 3.4 Total Re -pointing areas G. Maintain slightly recessed joint profile and do not overfill joints. 3.5 Wash A. Wash entire masonry surface with clean, potable water, no high-pressure spray, 300 psi max. and natural fiber bristle brushes to remove loose dirt and peeling coatings. Use appropriate chemicals suited for the materials where needed and rinse from bottom of the building to the top. Protect limestone with water to prevent acid from etching stone and rinse often. No metal buckets. Use ] part concentrate to 16 parts water. 04110 — Restoration Mortar 2.2 Mortar Aggregates; Avoid fine sand samples; beach, river, or agricultural sand with coarse aggregates should be used for the 1931/32 portion of the building. Different aggregates may need to be used depending upon the mortar types used for the 1952 and 1959 additions.