What is the brightness % of white?
Cougar White has a 98 Brightness
How thick is the 100# weight? What is the GSM of the cards? Would these be good for using as postcards?
The 100 lb cover weight is equal to 270 gsm and these would work fine for postcards. If you plan to print on them, you will need to be sure that your printer can handle the weight and the size of these cards.