acidic paper v.3:pt.1-v.3:pt.4,v.3:pt.6-v.4:pt.3,v.5:pt.1-v.9:pt.4 acidic paper pH pen test brittle covers v.5:pt.2-v.6:pt.3/4,v.8:pt.1-v.8:pt.4,v.9:pt.2-v.9:pt.3 brittle covers double fold test--breakage on second fold brittle paper v.6:pt.1/2,v.8:pt.1-v.9:pt.1 brittle paper double fold test--breakage on second fold
