The feature size of the matte vs shiny sides are much smaller than the wavelength of the bulk of the radiated light in either a microwave or conventional oven.

▲

bmicraft 2 hours ago | parent [-]

Is it? I can see the broiler glowing, so at least a decent chunk is close to visible light.

	▲	cwillu an hour ago \| parent [-]
		Look up the emission spectrum for a body at the temperature of a typical oven element: yes, it starts emitting some light that is visible, but the bulk of the energy is still in the IR band.