Porcelain is the premium end of the diffusion spectrum — and it is worth understanding exactly why. Four distinct diffusion processes are sold as 'frosted' or 'white' on the market, and they are not equal. Frosted (acid-etched): the inner glass surface is acid-etched into an uneven texture. Virtually no lumen loss, no CCT shift, but diffusion is weak — the filament is still partially visible and direct glare persists. Opal-white (internal powder spray): thick white powder sprayed inside and baked. Lumen loss 10–20%, CCT drops ~200K, noticeably softer — but the outer glass surface stays smooth and shiny. Sand frosted (external sandblast): grey matte exterior texture, lumen loss 80–90%, CCT drop ~200K, strong diffusion. Porcelain (external matte-white spray): the process used by premium lighting brands. Lumen loss 80–90%, CCT drop 100–200K — but diffusion quality is the highest available: fully scattered, uniform face, zero visible filament. You can look directly at a porcelain bulb at full brightness without discomfort. HongYu's ETL + FCC listed porcelain range applies this process across nine shapes in E26 and E12 base.