  Ellerman bombs are transient brightenings of the wings of the Balmer lines
that uniquely mark reconnection in the solar photosphere. They are also bright
in strong Ca II and ultraviolet lines and in ultraviolet continua, but they are
not visible in the optical continuum and the Na I D and Mg I b lines. These
discordant visibilities invalidate all published Ellerman bomb modeling. I
argue that the assumption of Saha-Boltzmann lower-level populations is
informative to estimate bomb-onset opacities for these diverse diagnostics,
even and especially for H-alpha, and employ such estimates to gauge the
visibilities of Ellerman bomb onsets in all of them. They constrain Ellerman
bomb formation to temperatures 10,000 - 20,000 K and hydrogen densities around
10^15 cm^-3. Similar arguments likely hold for H-alpha visibility in other
transient phenomena with hot and dense onsets.
