Show Glass Made to Protect Documents Fr From Fromthe Fr6mthe m mthe the Sun ; : an Aid to the Museum Curators The product on of document documentglass documentglass documentglass glass wh ch is designed to protect protectvaluable protectvaluable protectvaluable valuable manuscripts from the de deterloratIOn deterioration detenoration terloratIOn terioration caused by harmful 1 I ght ghtrays ghtrays ghtrays rays is announced says SCientific SCientificAmerican ScientificAmerican ScientificAmerican American Developed to meet a agrowmg agrowing agrowing growmg growing demand by museum dIrec dIrectors directors directors tors and curators of collections of ofrare ofrare ofrare rare manuscripts document glass glassfilters glassfilters glassfilters filters out the ultra violet portion of ofthe ofthe ofthe the spectrum exposure e"qosure eqosure e'cposure ecposure " ) ' to which whichcauses whichcauses whichcauses causes discolorat on or paper andfading and andfadmg andfading fadmg fading of mk Ink at the same time tunc giv givmg giving giving mg ing complete vis via bility bihty by transmit transmittmg transmitting transmitting tmg ting the visible light I1ght raysDevelopment raysDevelopment rays raysDevelopment Development ot of o1 document documem glass glasswas glasswas glasswas was based on the tact fact that the theultra theultra theultra ultra violet portion ol of the spectrum spectrumis is most destructive to paper stocks stocksand stocksand stocksand and inks of various kinds as es estabhshed established estabhshed tabhshed tablished in m research activities car carried carrued carried ried rued out at the Swedish Nat onal onalTestmg onalTesting onalTesting Testmg Testing institute mstitute in m Stockholm The Themost Themost Themost most active light rays are those be beyond beyond beyond yond the range of the visible spec spectrum spectrum spectrum trum in the short wave regIOn regIOnof regionof regionof of ultra violet ( shorter than 400 400mill 400mill 400mill mill microns ) Alter Arter After considerable exper menta mentat t on with chem chern cal ingred cnts ents de designed designed designed signed to transmit the visible I ght rays and filter out the ultra violet violetdocument violetdocument violetdocument document glass was perfected perfectedComprehensive perfectedComprehensive perfectedComprehensive Comprehensive tests reveal that It Ittransmits ittransmits ittransmits transmits only 3 per cent of the m in mvIsIble invisible mvisible vIsIble radiat radlat on just out of the VIS vie VISIble vieable visible Ible able range yet has a relatively very veryhIgh veryhigh veryhigh hIgh transmission within the vIsIble vIsIbleportion visibleportion visibleportion portion of the spectrum The chem chemical chemical chemical ical icalclements icalelements elements clements which give the glass glassits glassits glassits its non actinic act/me act me / quality impart to It Ita ita ita a very faint famt pink t tngc nge which Is Isno isno isno no way interferes with visib vlsib hty lIty htyWith lItyWith lityWith With the extremely low ultra ultraviolet ultraviolet ultraviolet violet transmission effected by doc document document document ument glass-by glass by glass - by tar far the lowest ob obtalnable obtamable obtainable talnable tamable with any glass of compar comparable comparable comparable able visible transmIssion-the transmIssion the transmission - the fad fadIng fadmg tading Ing mg of even the most del cately Gately col colored colored colored ored ink and the deterioration of ofthe ofthe ofthe the paper should be almost wholIy wholly wholIyprevented whollyprevented whollyprevented prevented |