Transparent for heads with a viscosity of light honey Semperfli No Tack UV dries as it says, with No Tack to its finish. It can be used to secure thread or deer or bucktail part way through a tie to allow you to continue tying without building up a profile or use it as a varnish replacement. Unlike some UV's on the market, the no tack finish means no need to varnish over the top to get a perfect finish to your fly. Use to create heads, as a layer over bodies Perdigon flies or as an alternative to superglue based flies.
The science bit - specially developed liquid monomers and oligomers are mixed with a small percent of photoinitiators, these are then stored in black UV resistant bottles. Exposed to UV energy in a few seconds the adhesives instantly harden to protect your fly.