Cleaning/restoring interior brick

Old 01-29-01, 10:10 AM
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How do you go about removing a tar(?) sealer that was placed on a brick chimney before plaster was placed around it? Brick is about 70 yrs old and I would like to have the brick exposed - trying to clean off this sealer and restore the brick.
Old 01-30-01, 12:53 PM
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Personally I would choose another interior solution.

Removal of heavy surface accumulation: crystallize by freezing with dry ice. Materials: dry ice, stiff plastic scrapers or a stainless steel scraper, a stainless steel wire brush, plastic brush or stripping pad, protective gear (heavy gloves, eye protection, a respirator, tongs or holder for the dry ice). The brick and mortar must be completely dry and full ventilation is a must. Some efflorescence may occur during this stage. ** Carbon dioxide from the dry ice is heaver than air and will collect at floor level. Remove children and animals from the area. Again, full ventilation is a must.

Next step: an intensive stone cleaner/stripper containing "potassium hydroxide". Stone Care makes this type of stripper. Read and follow directions, and blot, do not rub the surface. ** Potassium hydroxide is "caustic potash". It will burn skin, and adversely affect most surfaces.

Alternate products: heavy duty paint/graffiti stripper or adhesive remover. Any may leave a difficult to remove residue. Strippers containing "sodium hydroxide" (caustic soda) may cause more efflorescence.

Next step: a paste poultice. Obtain a quantity of "kaolin", or "diatomaceous earth" from a ceramics supply for the filler material. Suitable solvents for making the paste: kerosene, mineral spirits, acetone, xylene, and toluene. Mix filler & solvent to a paste, trowel on, cover with plastic, tape and seal in place, poke a hole or two in the plastic. Remove when completely dry (days not hours). Repeat as necessary.

Acetone, xylene, and toluene are fast acting solvents, highly flammable, and toxic. **Toluene vapors collect at floor level. An ignition source may cause an explosion. Nitrified toluene is the explosive TNT. Interior use: small patches only, with full ventilation. Kerosene and mineral spirits are slower acting solvents, less toxic than the former, are a little more difficult to ignite, but will tend to leave a gloss residue on the brick.

Final clean up: wash with TSP or TSP paste for deeper cleaning (TSP, filler, water). Rinse repeatedly and completely.

Spot cleaners: bug & tar remover, asphalt cleaners, STP brake parts cleaner. Typically bug & tar remover and asphalt cleaners contain "dipropylene glycol methyl ether" or "ethylene oxide".

Ethylene oxide is flammable, toxic, and a suspected carcinogen. Dipropylene glycol methyl ether decomposes hazardously in the presents of Carbon dioxide (the solid form is "dry ice") and other oxides of carbon. The main solvent in "STP brake parts cleaner" is "perchlorethlene". This is the same solvent used by dry cleaners. It is a federally regulated solvent, and toxic, but it maybe the lessor of the three evils. All of the solvents are toxic. None should be used in quantity, especially in confined unventilated areas.

Efflorescence treatment products are available at masonry supplies.

A very expensive hired solution is CO2 blasting. Portable CO2 blasting services are not common, however, it is nondestructive.

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