In addition to full whites with or without optical brighteners, it is sometimes desirable to reduce the natural coloration of wool for the dyeing of pastel and brighter yellow shades. This is sometimes achieved on a batch basis over night or with elevated temperatures in a more limited time. The pH should not exceed 9 as the rayon component may begin to saponify. The following procedure is a starting point and may be modified for various equipment and degrees of whitening necessary:
- Enter goods into bath containing the following chemicals and raise the temperature to 120-130°F(49-54°C).
- 1.0 % owb Sodium Silicate
- X % owb Soda Ash to a pH range of 8.5-9(Do not exceed pH of 9)
- 1.0 % owb Orcoterge ALK-N Conc™
- 2-2.5 % owb Hydrogen Peroxide 35%(2.25 gallon)
- Run at 120-130°F(49-54°C) for 45-60 minutes.
- Scour off at 100-120°F(38-49°C) in the beam, jig ,beck or continuous scour train. Re-acidify goods to pH of 5-5.5 with either acetic or sulfuric acid.