Do ultra-white gels not cure properly because they are so dense?

This is mostly correct, but there’s a twist. It has a lot less to do with “density” and more to do with the thickness of the UV gel layer. The thicker the white UV gel, the more difficult it is to cure. UV light has difficulty penetrating most substances — even pure water. With all UV gel products, a great technique is to use a thin layer of clear UV gel on the natural nail plate. This thin, clear layer will cure easily and provide a good base for proper adhesion. Then apply a thin coating of white UV gel on the free edge. This thinner white layer will cure more easily and the two layers at the free edge will provide enough thickness to resist cracking or breaking. -- Doug Schoon is vice president of science and technology for Creative Nail Design (Vista, Calif.).