You would think Intense and Archival black ink were the same thing when you look at the packages. they both say permanant, solvent based ink and acid free. Both are waterproof, but the main difference is the Intense Black is fast drying which essentially means you can start coloring just after you stamp it. If you were to use the Archival Black, you would want to wait until it dries.
Close to my Heart states their recommendations as:
Intense Black: Recommended for use with watercolors or alcohol markers.
Archival Black: Recommended for scrapbook pages and stamping on vellum.
The Black Close to my Heart Ink is waterbased, and only recommended when you are NOT using anything with it.
If you have any questions, please leave them below in the comment section.
Creatively,
Carol