A customer wrote in with a great question today and I thought I'd share it here for the benefit of everyone designing their own business cards.
I need to have business cards produced and was wondering about any font size/weight considerations that I need to be aware of while designing the cards. - Scott
There's no hard and fast rule about font weights. For example, Stonewood Spa uses a logo that has their 'boutique and apothecary' tag line as part of their business card mark.
You'll see that it is a bit lighter than you would chose for perfect legibility, but it is readable and it maintains the visual and messaging continuity with their other marketing materials.
The contact details, on the other hand, stand out nicely against the brown craft. This happens to be a 7.5pt Myriad Pro Bold, and I think you could safely use a Regular or a slightly smaller font size.