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1、Paper―MorethanMeetstheEyeA)Wearesurroundedbysomuchpaperandcardthatitiseasytoforgetjusthowcomplexitis.Therearemanyvarietiesandgradesofpapermaterials,andwhilstitisfairlyeasytospotthevarieties,itisfarmoredifficulttospotthegrades.B)Itneedstobeunderstoodthatmostpaperandcardismanufa
2、cturedforaspecificpurpose,sothatwhi1stthecorn-flakepacketmay1ooksmart,itisclearlynotsomethingdestinedforthearchives.Ttismadetolookgood,butonlyneedsa1imited1ifespan.Ttisalsomuchcheapertomanufacturethanhighgradecard.C)Papercanbemadefromanalmostendlessvarietyofcellulose-basedmate
3、rialwhichwi11ineludemanywoods,cottonsandgrassesorwhichpapyrusisanexampleandfromwherewcgettheword''paper〃?Manyoftheseareveryspecialized,butthepreponderaneeofpapermakinghasbeenfromsoftwoodandcottonorrags,withthebulkbeingwood-based.PaperfromWoodD)Inordertomakewoodintopaperitneeds
4、tobebrokendownintofinestrands.Firstlybypowerfulmachineryandthenboiledwithstrongalkaliessuchascausticsoda,unti1afinepulpofcellulosefibersisproduced.Itisfromthispulpthatthefinalproductismade,relyingonthebondingtogetherofthecelluloseintolayers.That,inaverysmal1nutshell,istheessen
5、ceofpapermakingfromwood?However,therealityisrathermorecomplicated.Tnordertogiveusourwhitepaperandcard,themakerswilladdbleachandothermaterialssuchaschinaclayandadditionalchemicals.E)Afurtherproblemwithwoodisthatitcontainsamaterialthatisnotcellulose.Somethingcalledlignin.Thisise
6、ssentialforthetreesinceitholdsthecellulosefibrestogether,butifitisincorporatedintothemanufacturedpaperitpresentsarchivistswithaprob1em?Lignineventuallybreaksdownandreleasesacidproductsintothepaper?Thiswillweakenthebondbetweenthecellulosefibersandthepaperwillbecomebrittleandloo
7、kratherbrownandcareworn?Wehaveal1seenthisinoldnewspapersandcheappaperbackbooks.Tthasbeenestimatedthatmostpaperbackbookswillhavealifeofnotgreaterthanfiftyyears-Notwhatweneedforourarchives.A)Sincethe1ignincanberemovedfromthepaperpulpduringmanufacture,theobviousquestionis"whyisit
8、leftinthepaper?"Theanswerliesinthefactthatligninmakesupaconsi