Shellac (E904)
A glossy coating from lac insect resin; the material itself is generally tolerated, but the process needs checking.
Why this is a critical point
Shellac is a secretion produced by lac insects on tree branches, not part of the insect's body itself, so most fatwa bodies tolerate it. What needs checking is the solvent used in processing it (often ethanol) and the possibility of it being blended with other animal-derived waxes.
Halal alternative
Halal-certified shellac with a verified solvent, or a plant-based coating (pure carnauba wax).