There is no uniform method to carry out caustic treatment since manufacturing technology for polyurethane yarn varies. Breaking strength, breaking elongation and immediate recovery vary depending on which type of polyurethane yarn is used.

A caustic treatment accelerator cannot be used. For caustic treatment with a liquor flow machine, 105°C is recommended. Hanging, liquor flow and continuous methods are the most popular procedures applied to caustic treatment devices.

Some factories apply alkali automatic metering devices in order to carry out stable caustic treatment in the liquor flow method.