Dull gels can be caused by a few different problems. The most common have to do with curing, file grit, and oil residue on the nail. If gel is not cured for the entire recomm-ended time, it can appear dull. Always follow the manufacturer’s suggested time. Also, not all UV lamps are the same wattage, and some gels require a higher wattage than others. This leads to the most common problem: The bulbs in a UV lamp should be changed after a certain number of hours determined by the manufacturer. A good rule of thumb is twice a year. We change our bulbs when we change our clocks for daylight saving’s time.
Also remember that gel needs a dry, rough surface on which to stick. A coarse-grit file is needed with most gel lines in order to have proper adhesion. If the surface is not entirely roughed up, the gel will sit differently, and when cured, this could cause it to appear dull. -- MaeLing Parrish