We share a kitchen with around 20 people on our office floor. The problem is that some people leave their dirty cups and plates in the sink and on the tables even though we have a dishwasher. Each week two people are in charge of cleaning the kitchen. However, this job is only to clean the surfaces, start the dishwasher. and then unload it. There have been several emails, but they have had no impact on the issue. What can be recommended to improve or correct the situation?
[Update]
The problem at our kitchen is that there are a few people who cook and heat up food in the microwave, and the rest - including me - who would either never use it or only make coffee. Therefore, one plate would not work. As the frequent users would just use the plates of the people who don't use the kitchen. Also the surfaces and the microwave tend to get dirty quickly. Our boss does not use the kitchen, and I don't want to spend my time leading by example when I am hardly using the kitchen.
The main annoyance (for me) is, that it is our only social area and so you have to sit in this dirty kitchen when you want to have a chat.