Quote Originally Posted by The Deadlifting Dog View Post
That's not what I said...
Some find that prop hurts like a bitch.
It's not the length of the ester but what what it is.

Also, PIP can be caused by the solvents used.
OP Deadlift gave you a solid response.

To expand on it further, after you inject an esterified steroid the esterase enzyme splits off the ester resulting in hormone and acid.

In the case of prop you get testosterone and propionic acid.

Solvents can cause or help prevent PIP.

For example, ethyl oleate (EO) is a plasticizer used in the molding industry and is sometimes used as a numbing agent in some intramuscular drugs.

This may be why you didn't experience any PIP when mixing compounds.

My experience with PIP has been if you pin before working out that muscle group after a few times you no longer get any discomfort even if not working out.