Treatment of quartz glass surfaces; treatment of ceramic surfaces; applying partial opaque reflective coating onto fused silica parts, possibly lamps, windows, tubes, reactor chambers; applying partial coatings onto fused silica parts, especially applying partial coatings onto parts for lamps, windows, tubes or reactor chambers; applying partial reflective coatings onto fused silica parts, especially applying partial reflective coatings onto parts for lamps, windows, tubes or reactor chambers...