Ask Mr. Wizard

T90 vs. T45 Hop Pellets

TroubleShooting

Sam Schalley - Rochester, Minnesota asks,
Q

I recently noticed that hop pellets are described as either T90 or T45. What do these values mean? What are the pros and cons of each? Is it possible to tell which you’re purchasing from homebrewing stores (I have not seen the values used in hop descriptions)?

A
The Wizard explains how hop pellets are made and the effect different types of light have on wort and beer.
Response by Ashton Lewis.