yes. direct connection between battery and solenoid causes the valve to open. I did notice that the bag containing the transistor is labeled as 60V rather than 100 (which is what the datasheet was saying)

I'll have to get back to you on that, no 10k on hand. I tried 5 1k and 5 560 Ohm all in series (7800 total) with no difference. I did verify my solenoid / battery combo works by hooking positive / negative directly to the valve which subsequently clicked open.

@joan No. Switching it over to RPi Pin 1 has no effect

Ok thanks for the update, I'll go ahead and mark as accepted. I ask because I only have 2mos experience as an electrical hobbyist :)

I initially marked this as accepted but then took it back. I'll mark it again if you can update with any general guidelines on how to come up with the design considerations when looking for the MOSFET specifically, but I'd also appreciate any info on how you came up with the values for the resistors. What would change if I upgraded to a 24V battery with a 24V solenoid valve?

Thanks for the advice Milliways, it is much appreciated. The only MOSFET transistor in the drawer at the local store was a 60V one which I just went ahead and picked up thinking it was way overboard, now I'm glad I did.

:) Thanks Ghanima. I asked here mostly because this is specifically for a raspberry pi. I thought to go to Electronics.SE, but I hadn't yet asked a question here yet