The restoration of limestone has traditionally been accompanied by a search for the appropriate products. Standard HF (hydrofluoric) restoration technology can have unpleasant results. The fluoride ion has an affinity for calcium. The ion initiates cycles of degradation that are virtually impossible to halt, as the fluoride ion cannot be removed. Even the safer "fluoride salt" products have this residual problem. Further complicating this issue is the porosity of the stone and its tendency to develop deep stains of distinctly different natures. The first is environmental staining relating principally to urban pollution and its reaction to the calcium. This usually results in black streaks or black crust. The second problematic set of stains is the rain and heat cycle, which results in black shadows deep in the stone. We have developed four easy-to-use products that are almost 100% effective. The only situation where this chemistry has not been proven effective is when abrasive blasting has damaged the limestone. This process seems to open the stone in such a fashion that the chemical cleaning process has no chance of being successful. We strongly advise against abrasive blasting on any kind of stone or brick.
Many hospitals have been cleaned with OneRestore® while they were open and contractors have not had to cover air intakes. NMD 80 has been tested by OSHA and various other officers on government jobs, especially military bases, and has found that respirator protection was not needed when used at proper dilutions. I personally have found the odor of Stripper Cream to be most pleasant in use. The D-Limonene gives off a very pleasant odor while the stripper is being used.
OneRestore® and Heritage Restorer have been proven time and again to be safe for glass and anodized aluminum frames. Simply do not allow the products to dry on the surfaces, rinse while wet. OneRestore, an acidic based cleaner, is not only safe for glass and anodized, but will clean them as well. OneRestore® and Heritage Restorer are great choices for restoring limestone since there is no need to cover windows or frames. We do not recommend the use of Stripper Cream on glass or anodized frames.
This is a special application that requires communication with the manufacturer. We have seen though that NMD 80 has removed a variety of problems caused by other products. This would include streaks and burns on sensitive stone, block and brick. NMD 80 actually removed the stone whitening and allowed the uniform result achieved by then cleaning with OneRestore®.
There are some common misconceptions concerning the use of strong acids (such as hydrochloric acid) on limestone.
The Indiana Limestone Institute literature states:
“Special consideration and protection shall be provided when brickwork is cleaned above the limestone. Strong acid compounds used for cleaning brick will burn and discolor limestone. Use of sandblasting, wire brushes or acids will be permitted under special circumstances, approved by an architect.”
The common misconception is that if a product is acidic in nature (with a pH less than 2.5), it should automatically be banned for use on limestone. because it would fall under the classification of strong acid and would do the type of damage indicated in the statement issued by the Indiana Limestone Institute. This statement would be true if using strong acids in their raw non-reacted state. Our modern limestone cleaners (OneRestore® and NMD 80) have been formulated and blended to successfully incorporate strong acids coupled with surfactant packages that clean without adverse effects on limestone. Throughout the country, OneRestore® has been successfully used to clean historic limestone as well as buildings that have limestone on their windowsills or as one of their components. Our new masonry detergent, NMD 80, which contains a greater amount of the buffered strong acid than OneRestore®, has been used to clean new and historic buildings that are made up completely of limestone and those that contain limestone as one of their components. Repeated inspections of these cleaned structures have been done over more than a four year period and have shown no apparent etch or discoloration has occurred. This etch and discoloration would have occurred and been grossly visible if the limestone had been cleaned with raw HCL or a similar “strong acid” type product.
OneRestore® and NMD 80 do not cause discoloration or etch on limestone. EaCo Chem provides blended products that contain a mixture of acids and surfactants without the adverse effects that are typical of products, which use raw acids as their main component or in an unblended state. Acid is just one of the many components in OneRestore® and NMD 80 and is why we feel it is appropriate to evaluate them on performance and safety issues, rather than on what the raw materials could, do because in their finished state, the problems associated with low pH products do not exist.