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Smith, Watson

"The Chemistry of Hat Manufacturing Lectures Delivered Before the Hat Manufacturers' Association"

No doubt on adding fresh copperas further precipitation of
iron will take place, and so this ochre-like precipitate will
accumulate, and will eventually come upon the hats like a kind of thin
black mud. Now the effect of this will be that the dyestuff, partly in
the fibre as a proper dye, and not a little on the fibre as if
"smudged" on or painted on, will, on exposure to the weather, moisture,
air, and so on, gradually oxidise, the great preponderance of iron on
the fibre changing to a kind of iron-rust, corroding the fibres in the
process, and thus at once accounting for the change to the ugly brownish
shade, and to the rubbing off and rapid wearing away of the already too
thin superficial coating of dyed felt fibre. In the final spells of
dyeing in the dye-beck already referred to, tolerably thick with black
precipitate or mud, the application of black to the hat-forms begins, I
fear, to assume at length a too close analogy to another blacking
process closely associated with a pair of brushes and the time-honoured
name of Day & Martin.


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