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Molecular Traps

 

As important as alkaline buffering is, conservation scientists now realize it does have important limitations. Alkaline buffering does not deliver the degree of protection we once assumed it provide to our collections. If an acid migrates to, or arises from within (in the form of a by-product of deterioration), or forms from a pollutant coming into an alkaline buffered paper, and, if this acid is in contact with a particle of alkaline buffer, the acid will be neutralized. However, if the deteriorative molecule is an oxidative species such as a peroxide, or an acid precursor like an oxide of nitrogen or sulfur dioxide, or a pre-acidic by-product of deterioration, it will not react with the alkaline buffer. Instead it continues through the paper housing (i.e, box, envelope, folder, mount board, etc.) and damages the artifact you are attempting to protect. If a suitable molecular trap is contained within the alkaline buffered paper, it can capture and remove those harmful molecules which passed by the alkaline buffering. Our General Purpose MicroChamber Paper and MicroChamber boxboards (except the MicroChamber/Silversafe boards) contain both activated carbon and our SPZ zeolite. The black side of the General Purpose MicroChamber paper (also used in the MicroChamber boxboards) contains alkaline buffers and an especially effective activated carbon. The white side of the paper contains alkaline buffers and our modified proprietary hydrophobic, acid-resistant SPZ zeolite which we developed and engineered after extensive research to perform the specific functions necessary to protect your collections. Our SPZ zeolite removes acids, aldehydes, ammonia, pollutants such as SO2 and NOx, and despite the incorrect information seen in a competitor’s catalog, it does remove oxidative gases, even in very low concentrations (see doorway and bus photos subjected to ANSI standard IT 9.15-1992 oxidative gas tests in MicroChamber test section on our website. This SPZ zeolite was engineered to remove all of the known deteriorative molecules that threaten our collections, even those with very low polarization levels.

 

Efficacy of Molecular Traps in MicroChamber Papers

 

Acids:

It is interesting to note that our molecular traps are significantly more effective than an alkaline buffer at removing acids, and unlike buffered-only papers, they will remove by-products of deterioration such as aldehydes which form acetic acid. This is important because acetic acid is the primary by-product of deterioration produced both by paper and by photographic materials. One of the most dangerous pollutants to paper is acetic acid As the effects of acetic acid build up in a paper artifact, it accelerates degradation My goal was to identify materials that would be most effective at absorbing and retaining acetic acid, and that would be suitable for use in preserving artifacts. I looked at about 18 different materials, including activated carbon, clays, calcium carbonate, and several zeolites The activated carbon and one of the zeolites-called SPZ, (the zeolite Conservation Resources developed for use in Artcare board, conservation boards, papers and materials) performed significantly better than the other physical adsorbents … based on its adsorption and retention of acetic acid-which can be assumed to inhibit cellulose deterioration-the SPZ zeolite, incorporated in Artcare (and) MicroChamber technology (products), is a very viable material for preventative conservation applications. 1

 

The results from our tests using gas chromatography show that if we have equivalent papers-for example a 65 g/m2 interleaving paper, or a 130 g/m2, .006" thick envelope paper, or a standard 250 g/m2 archival file folder paper in both MicroChamber paper and buffered paper, the MicroChamber papers have 170 times the acid-removal capacity of the buffered papers. In other words, the buffered paper would have to be replaced 170 times before you would need to replace the MicroChamber paper.

 

1. From an interview with James Druzik, Senior Scientist, the Getty Conservation Institute, printed in the October 2003 Decor magazine.

 

By-products of deterioration:

MicroChamber papers are very effective at removing pre-acidic by-products of deterioration, such as aldehydes. These pre-acidic deteriorative by-products pass unaffected through traditional buffered paper because the deteriorative by-products do not react with the alkaline reserve in buffered papers. If we assume all of the acetaldehyde (a precursor to acetic acid) removed as deteriorative by-products by the MicroChamber paper will become acetic acid, we find the MicroChamber paper can remove what would become 231 times as much acid as would form if only the buffered paper were present.

 

Pollutants:

MicroChamber products do provide protection against common oxidative and acid gaseous pollutants such as ozone (O3), oxides of nitrogen (NOx, NO, NO2), sulfur dioxide (SO2), as well as H2S, CS2, ammonia, formaldehyde, peroxides and a great many other such molecules which can harm collections. The traditional alkaline buffers in conservation papers do not react with or remove these deleterious molecules. Furthermore, such molecules can pass unaffected through even the thickest buffered boards 2, where they can contact and damage collections housed within these buffered boards and papers. If, for example, we look at New York City and at Los Angeles, the EPA (The U.S. Environmental Protection Agency) gives us the maximum hourly rate of a variety of pollutants measured in these two cities for one year. Using these maximum concentrations, we can calculate the maximum amount of a pollutant such as SO2 in one liter of air. Exposing a 24 x 36 MicroChamber folder to a fresh liter (slightly more volume than a quart container) of polluted air every hour, we find, at the maximum hourly concentration level of pollutants measured in New York and Los Angeles, the MicroChamber folder has the capacity to remove the SO2 in NY city for 8219 years, and in LA for 26,224 years. Obviously if the air exchange is increased this figure will be lower. For example, if the air flow rate into the folder was increased to 10 liters per hour, the figures would drop to 1233 years for NY City and 3933 years in Los Angeles, CA. Of course the MicroChamber product will also pick up other harmful molecules, in addition to the SO2. Therefore to the extent these other molecules are present and removed, the maximum quantity of SO2 which can be removed will be lowered-but these figures do at least provide a point against which you can form a comparison between the effectiveness (zero) of buffered products and of MicroChamber products.

 

The preservation advantage offered by our new MicroChamber boards and papers, which contain both specialized proprietary molecular traps and alkaline buffers, is quite striking. While traditional alkaline buffered conservation papers and boards do provide an advantage over acidic commercial products, this improvement does not begin to approach the phenomenal gain in protection offered by MicroChamber products over traditional alkaline buffered products. Alkaline buffered paper is a technology of the 1960s. MicroChamber materials give you the advantage of technology from the 1990s. MicroChamber products offer new opportunities in preventative conservation, increased life and thus reduced preservation costs for all collections. See the MicroChamber product verses traditional buffered-only test results on our website.

 

2. Guttman, C. M. and Jewett, K. C. 1993 “Protection of Archival Materials from Pollutants: Diffusion of Sulfur Dioxide through Boxboard”, Journal of the American Institute for Conservation 32:81-91. Also, see MicroChamber test section on our website.