I just received my diploma from my university. I'm very happy and my results aren't that bad either. Now, as the result is already known, I would like to thank my professor and my supervisor for their support.
Would it be acceptable, if I make them a gift to express my thankfulness?
I was thinking of a bottle of a good liquor for both of them.
The safest way to express your gratitude is to (hand)write a thank-you-card. In all likelihood that will be appreciated just as much as a gift, and is guaranteed not to cause any trouble.
I would suggest avoiding anything as substantial as a bottle of liquor. However a small gift is generally seen as acceptable. Such as a mug/cup, biscuits, or as has been stated a hand written thank you card would be fine.
Don't go too over the top as it may cause an issue for the professor/supervisor either in terms of admin problems, or just making them feel a little awkward.
In our case, it's a strict no, no matter whether before or after examinations. We would have to relinquish the gift and do a lot of tedious paperwork to document how we were or may have been influenced by the gift. In other words, not only would we not enjoy the gift, the attempt to please us would end with punishing us with a lot of tedious paperwork. I can imagine this to be the case in many institutions.
Why after the examinations, too? I assume the reasoning is that, if it gets known that gifts are expected/accepted, there may be an incentive to pre-announce them. So, the policy is strictly no gifts.
@MaartenBuis' response is thus by far the best one: a nice thank-you card will always please your professor and not cause any trouble.
