Residual resin, reversible treatment

Residual resin percentages in Table III are given both before and after correction for the amount of extractives, which are presumed to have been extracted along with the consolidant. In several cases the uncorrected values are negative, which would be expected if all consolidant and some extractives had been removed. After the correction, the only negative value is for the AYAT-acetone system, which must therefore be considered the most reversible. The least reversible treatment was the Butvar B98-toluene-ethanol system, especially when removal was attempted by soaking only, which left corrected residual resin of 5.7%. For AYAT and Acryloid B72, the polar acetone was much more effective than the nonpolar toluene in removing consolidant. 

Sulfite paper has a relatively short life span, since residual acid will continue to hydrolyze the cellulose and cause embrittlement. Further sources of acid include aluminum sulfate (which is added together with resin to suppress bleeding or feathering of ink into the paper) and S02 and NO from the atmosphere. Much of the world s library collections and archives will soon be lost as the paper crumbles. Various deacidification treatments (e.g., with ammonia, morpholine, cyclohexylamine carbamate, or diethyl-zinc) have been proposed and tried, but at best they can only halt the process of embrittlement and cannot reverse it.14 With the move to kraft pulping, alkaline peroxide bleaching, and increasing use of precipitated calcium carbonate as a filler, the high quality papers produced today are intrinsically acid free and should also resist subsequent acidification by S02-polluted air fairly well. 

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