True Brass vs Boiler Black

How close are they?

ΔE 29.0, loose: different enough that you should pick on purpose. Boiler Black is noticeably darker, much more muted than True Brass.

Can I use Boiler Black instead of True Brass?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Boiler Black is noticeably darker, much more muted than True Brass.

Can I use True Brass instead of Boiler Black?

The same difference applies the other way round: True Brass is noticeably lighter, much more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.