Q&A: Question on etiquette after PhD Defense at TU Delft

Some time ago, I received a reader question. I actually wasn’t able to reply on time because my mailbox got so full, but I still think it’s an interesting question to address. Here’s the question, edited for anonymity.

Hello Eva,
Thank you for your posts. I am defending on Some Date. Since I am not from Holland (I did my PhD remotely from the USA), I was not sure about the etiquette regarding the reception and dinner. Is it expected that I take the entire committee out for dinner after the reception? Or only my promoters? How about their families?
Regarding the reception, how much food is considered appropriate? I am expecting less than 50, but planning for about 25 tea/coffee/pastries + 25 orange juice/water/sandwiches + 25 beer/wine/snacks/nuts/pretzels. Would something like this suffice?
Appreciate your thoughts, and sorry for so many questions!
Regards,
A Reader

Let me take this question by question:
Is it expected that I take the entire committee out for dinner after the reception? Or only my promoters? How about their families?
Yes, it’s indeed expected to invite the entire committee and extend the invitation to their partners. Most of your committee members may need to travel back home and won’t be able to make it, but it’s expected to invite all committee members. Looking back at my defense, of the 8 committee members, 5 joined the dinner (3 with their spouse).

Regarding the reception, how much food is considered appropriate? I am expecting less than 50, but planning for about 25 tea/coffee/pastries + 25 orange juice/water/sandwiches + 25 beer/wine/snacks/nuts/pretzels. Would something like this suffice?
Yes, that sounds appropriate indeed! I remember I ordered too much food (but my defense was at noon, so I couldn’t gauge well if everybody would want a sandwich or not). The other part of uncertainty is that, since the defense is public, it’s sometimes difficult to know who will show up (and how many people will be there for the reception).