Sometimes after the use of pressure cookers,the inside of it will 
have stains which is very difficult to remove even after hard 
scrubbing....Try this out then!!!

Cut one lime into two halves.In the cooker add 1/4th of water and 
lightly squeeze this limes into it and put both pieces in it.Close 
the cooker and bring into boil.Wait for one or two whistles....

See the magic...All the stains will go easily..!!!