I have two 150watt HPS fixtures that I got back around 1990. I have a full case of replacement bulbs but they are frosted/coated. Does it matter if the bulbs are coated? There is a difference in appearance but does that matter? Thanks for any info. !
If the only difference between your bulbs and other, equivalent HPS bulbs is that yours have "frosted" glass, I would expect that there wouldn't be any difference from the plants' perspective because the frosted bulb would simply diffuse its light a little bit compared to a clear glass bulb.
