I always clean my bulbs and use disposable white gloves or a clean towel. Any oil will may cause problems. A clean globe is a happy bulb, but will admit I have installed a few hundred industral bulbs and never had a problem. But on my own systems I always keep it clean and oil free. Note MH bulbs if the outside globe is broken never use it. It puts out UV and will cook you skin eyes, and plants. The vicor glove stops UV from being emitted.