Completing+the+Polarization+Test+
How+to+Make+and+Use+a+Film+Viewer+
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The!film!viewer!is!valuable!tool!for!distingu is hing!polyester!film!supports!from!cellulose!acetate !
and!cellulose!nitrate!film!supports!in!a!simple!and!no‐destructive!manner!(NOTE:!It!cannot!
distinguish!between!cellulose!nitrate!and!cellulose!acetate).!This!information!is!important!to !
know!when!considering!your!park!unit’s!cold!st orage!needs,!as!B&W!polyester!films!are!
significantly!more!stable!than!cellulosic!film!supports!and!do!not!need!cold!storage.!Therefore,!
such!materials!may!be!stored!in!normal!environmental!conditions!(70!degrees!/50%RH)!within!
museum!storage!spaces.!Ultimately,!this!may!save!considerable!space!within!a!freezer!
compartment!or!cold!storage!vault.!
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Instructions+on+How+to+Make+a+Film+Viewer+
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Materials+Needed:+
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• Polarizing!Filter!sheet!film!(available!at!phot o!supply!stores)!
• Archival!Mat!Board!
• 3M‐415!Clear,!Double‐sided!tape!(1/4”!width,!recommended)!
• Tyvek!tape!(2!¼”!width,!recommended)!!
• Scissors!
• Scalpel/blade!or!Exacto!knife!
• Paper!cutter!or!blade!for!cutting!mat!board!and!polarizing!filter/film!
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To+make+a+6”+x+8”+viewer+tool:+
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1.! Cut!mat!board!into!two!6x8”!pieces!!
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! Cut!two!3x3”!square!pieces!of!polarizing!filter/film!!
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3.! With!mat!board !lying!flat,!use!scalpel/blade!o r!Exactor!knife!to!cut!out!a!2x2”!square!in!
lower!right!corner.!Square!should!be!1!inch!from!each!edge.!Cut!these!in!both!mat!boards.!
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4.! Place!one!board!on!top!of!the!other!so!the!square s!match!up!(th is !is!how!the!mat!
boards!will!look!when!taped!together.!You!will!be!able!to!open!it!like!a!book.!
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5.
! Place!one!small!piece!(approximately!3!inches!long)!of!clear!double‐sided!tape!above!
each!side!of!the!open/cut!square!on!the!mat!board!(this!wi ll!hold!the!polarizing!filter/film!in!
place!over!the!square!opening).!Place!one!piece!(3”!square)!of!the!polarizing!filter/f ilm!ov er!the!
cut!square!so!it!lies!on!top!of!the!clear!tape.!This!will!be!the!inside!of!the!viewer!tool,!as! if!you!
were!opening!a!book.!
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6.! For!the!second!mat!board,!you!will!need!to!match!up!the!polarizing!filter/film!at!
opposite!directions!so!that!when!you!have!the!two!boards!on!top!of!each!other!and!“close!the!
book,”!the!square!will!be!dark.!When!you!have!the!square!piece!of!filter/film !properly!in!place!
over!the!cut!square!in!second!mat!board!(wh ich!will!now!be!underneath!the!board!you!just!
completed),!you!can!adhere!it!using!the!clear!tape!(use!the!sam e!procedure!indicated!above).!
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7.
! Place!the!boards!on!top!of!each!other,!with!the!cut!squares!on!top!of!each!other!on!the!
lower!right.!Confirm!the!cut!square!is!dark.!The!Tyvek!tape!will!be!used!to!hold!these!two!mat!
boards!in!place!(like!the!binding!of!a!book).!If!you!were!to!open!the!book!and!lay! it!flat!with!the!
open!pages!facing!down,!you!would!be!taping!the!spine.!Place!the!piece!of!Tyvek!lengthwise!
over!the!center!(the!“spine”!area),!with!about!an!inch!on!each!board.!Turn!the!taped!boards!
over!and!tape!the!“inside!of!the!spine”!the!same!wa y.!The!mat!boards!should!now!be!held!
together!securely!with!the!Tyvek!tape!on!both!sides.!
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8.! Close!the!book!and!be!sure!the!cut!squares!match!up!and!the!square!is!dark.!!
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NOTE:!If!the!square!is!not!dark!when!closed,!then!you!have!the!filters!positioned!at!the!same!
orientati on!which!is!not!correct.!You!need!to!remove!one!and!re‐position!it!so!it!is!at!the!
opposite!orientation.!That!is!the!ONLY!way!the!tool!will!function!properly!when!viewing!films!
between!the!boards.!
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Instructions+on+How+to+Use+the+Film+Viewer
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To!use!the!viewer,!open!it!(like!a!book)!and!place!the!film!over!the!polarizing!filter!(window)!to!
the!right.!Make!sure!to!select!an!area!of!the!film!that !has !thin!or!no!image!making!material,!
such!as!an!outer!edge,!to!be!within!the!window!frame.!Otherwise,!you!will!not!be!able!to!see!
through!the!film.!Close!the!viewer,!hold!it!up!to!a!lig ht !source!(or!place!it!on!a!light!table)!and!
look!through!the!window.!You!may!need!to!tilt!the!viewer!back‐and‐forth!or!move!the!film!
slightly!in!the!viewer!to!observe!color!changes.!!
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• If!the!film!base!is!polyester,!you!will!notice!red!and!green!interference!colors!(rainbow!
patterns!like!a!soap!bubble)!and!the!film!will!appear!brighter!and!clearer.!
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• If!the!film!base!is!cellulosic!(acetate !or!nitrate),!there!will!be!no!interference!colors,!and!
the!window!will!be!dark.!
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References:!
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Bennett,!Karen!L.!and!Jessica!S.!Johnson!(1999)!NPS!Conserve!O!Gram!14/9!–!Identification!of!
Film‐Base!Photographic!Media!
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Fischer,!Monique!C.!and!Andrew!Robb!(1993)!Guidelines!for!Care!and!Identification!of!Film‐Base!
Phot ographic!!Materials.!!Available!online!at!
http://palimpsest.stanford.edu/byauth/fischer/fischer1.html!
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Reilly,!James!(1993)!The!IPI!Storage!Gu ide!for!Acetate!Film.!Rochester:!Image !Permanence!
Institute!
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