CHAPTER XVIII

DEFECTS IN SHEET RUBBER

Defective coagulation--Coloured surface blotches--General darkening of surface--Soft coagulum--Spongy underface--Tearing --"Pitting" of surface--Thick ends or edges--Mis-shapen sheets --Thick patches--Torn sheets--"Dog-ears"--Creases--Greasiness of surface before smoking--Surface blemishes--Uneven appearance--Variation due to oxidation--Colour when dry-- Surface gloss--Dull surface--Moist glaze and greasiness-- Virgin spots--Surface moulds or mildew--Black streaks or spots --White or grey streaks--Rust--Theories on formation of-- Prevention of--Two methods--Other views on causation--Bubbles --Causes of formation--In the field--In the factory--Blisters --"Spot" disease in sheet rubber--Support marks--Stickiness-- Surface pattern--Sheet clippings--Other infrequent defects-- Dirt--Ash--Bark--Splinters 249