First partial mash was a diacetyl disaster

[Earl_Grey]

The first partial mash i did was an irish red ale.

I am not positive what happened but its been kegged for about 2 weeks and i can detect a good dose of diacetyl.

What are some things that could have caused this? The yeast i used was safale s04 if that makes any difference. It was fermented 60-65F.

 

[VTDuffman]

Diacetyl could be due to old yeast or insufficient aeration. What was your lag time?

 

[Earl_Grey]

It was around a day. I aerated by shaking the carboy with cooled wort