Lots of experimenting......the cotton shirts on their own made good paper when it had been beaten for 60 mins, 45 mins. 30 mins would be fine if the sheets were thicker.
Adding 60 min cotton really helped to make a stronger sheet that would be usable to letterpress or screen print on......not so sure about etching.
The cotton shirts that were beaten for 30 mins and added to the cotton and made a nice all over distributed effect. The 15 min cotton was very chunky and difficult to make a good sheet but it may be useful in creating unusual pieces.