First, a bit of background:
I am a recent graduate from university looking for employment at a laboratory space that is associated with the university that I graduated from. This space is known for hiring students with my degree right out of graduation, and for working with them if they want to apply to a graduate program in the future, as I do. There are a few positions available that I am qualified for and are interested in applying to. However, I am also currently hired in a separate lab space, which takes up around 10 hours of my time every week
My problem comes from the space I am already hired at. I greatly enjoy my work there, and my supervisor is a respected individual in the field that I am interested in applying to graduate school for. He has promised me a letter of recommendation for the work I am doing with him, so I absolutely wish to keep working there for as long as possible. However, this leaves only 30 hours a week for my potential employment at this new lab space, and all of the positions I am going to apply for are listed as full time.
While I know that requesting fewer hours has a good chance of hurting my chances to be hired, I think that it is still more important to apply and be open about this restriction, than to not apply at all. My question is this:
Should I mention this restriction in my cover letter, being open about it up front, or should I wait until any potential interview and bring it up then?