You have a sentence with two different fonts, bold or italic, for example:
"How to solve a baconian cipher"
The message is 25 letters, of which letters number 5, 14, 17, 18, 20, 22 and 23 are bold.
Write them as A for not bold and B for bold letters, in groups of 5:
1) AAAAB 2) AAAAA 3) AAABA 4) ABBAB 5) ABBAA
The Baconian alphabet consists of a different combination of A's and B's for each letter of the alphabet (two versions available).
FIRST VERSION with I=J and U=V (used in the example text):
Decoding the five groups above gives:
1) B 2) A 3) C 4) O 5) NYour decoded message is: BACON
SECOND VERSION (using a unique combination for each letter):