We studied the bleaching potential of a highly reductive chemical: sul
furated borohydride, also known as the Lalancette's reagent, on a spru
ce/fir softwood TMP. The influences of reaction time, temperature, pul
p consistency and reactant concentration on pulp brightness were studi
ed. A very fast reaction was observed, along with an adverse effect of
high temperature on brightness. High reactant concentration increases
brightness gain. Sulfurated borohydride was compared to sodium hydros
ulfite and sodium borohydride. The Lalancette's reagent bleaches pulp
to the same level as sodium hydrosulfite, but lowers the yellowness of
the pulp to a greater extent.