Polished Silver vs Hammered Copper

How close are they?

ΔE 18.0, loose: different enough that you should pick on purpose. Hammered Copper is noticeably lighter, more saturated than Polished Silver.

Can I use Hammered Copper instead of Polished Silver?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Hammered Copper is noticeably lighter, more saturated than Polished Silver.

Can I use Polished Silver instead of Hammered Copper?

The same difference applies the other way round: Polished Silver is noticeably darker, more muted.

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.