Ornamental Horticulture

(2) Bleaching

Bleached ornamental plant material provides a striking contrast when arranged with dried or dyed flowers. Bleaching also allows the use of dyes for colouring. Oxidative (Hypochlorite, Chlorite and Peroxide) and reductive bleaching chemicals (Sulphite and Borohydride) are used for bleaching ornamental flowers and foliage. Profitability is depended upon attainment of high white quality and on cost efficient utilization of expensive bleaching chemicals. Sodium Chlorite is an excellent bleaching agent because it is relatively selective for lignin without damaging fibre. Optimum pH (4.5-3.5) and temperature (70^oC) is to be maintained for effective chlorite action. Hydrogen Peroxide may be more practical for some plant materials because it is less expensive.
Sodium Chlorite 10 % solution at 70 ^oC is ideal for complete colour removal of pink Gomphrena flowers in to pure white flowers at 7 hours of immersion. Hydrogen peroxide 30% also takes 7 hours for complete colour removal of Gomphren.