Radiation occurs when there is a transfer of heat through electromagnetic waves. While radiation plays a minor role in filter coffee brewing, it can still contribute to heat loss during the brewing process.

Temperature is the primary control variable in coffee extraction. It dictates the solubility of compounds and the kinetics of diffusion.

Deff=D0exp(−EaRT)cap D sub e f f end-sub equals cap D sub 0 exp open paren negative the fraction with numerator cap E sub a and denominator cap R cap T end-fraction close paren Eacap E sub a is the activation energy of the specific coffee solute. is the universal gas constant.

The mass percentage of soluble solids in the final liquid beverage.

EY (%)=TDS (%)×Mass of Liquid Coffee (g)Mass of Dry Coffee Grounds (g)EY (%) equals the fraction with numerator TDS (%) cross Mass of Liquid Coffee (g) and denominator Mass of Dry Coffee Grounds (g) end-fraction The Universal Coffee Control Chart

[ t = \frac2\eta L^2\gamma r \cos\theta ]

Freshly ground coffee is hydrophobic due to trapped CO₂ from roasting. When water first contacts grounds, it beads up (high contact angle > 90°). As CO₂ escapes (the "bloom" phase), the contact angle decreases. Water then enters the particle’s pores via capillary action, described by the Washburn equation: