1st Reason: You need to separate the color clothing from the white clothing because if they are washed together the white clothing will become off-white due to the colors released by the color clothing during the washing. 2nd Reason: We have dedicated washing programs for Cotton/ Synthetics/ Delicates/ Hand Wash/ Woolens/ Silk/ Bedding (option depends on the model selection) in the washing program knob. All the programs will have their own cycle of washing e.g. load size/ temperature/ spin speed and duration of washing for optimized washing performance. Therefore, if you are washing bath towels that are thick in texture and silk which is delicate and thin in texture, you cannot mix them to wash as the temperature/ spin speed/ duration of washing are different for best washing performance and to ensure optimal care for your precious laundry. The silk material which requires delicate washing may risk being damaged if you wash under the cotton program.   For more information on things to consider before buying a washing machine, check out Zanussi Washing Machine Buying Guide .