UV light professionals recommend customized UV flashlight for fly tying.
A 365nm wavelength UV flashlight is, in most cases, the best option,
optimally suited for UV resin curing. The 395-405nm UV LED lights that
are now commonly used do not provide as much light in the wavelengths
that best activate the resin. The Gulff 365nm wavelength LED produces
a spectrum of light that best matches the absorption spectrum of the
photoinitiator that is in most UV-curable resins. The Gulff flashlight’s
UV light appears whiter than the light of 395nm lights. This is because
the human eye cannot discern UV light when the wavelength is clearly
below 400nm. In this case, the light only becomes visible when it strikes
a surface that reflects UV light. Experts do not recommend using inexpensive
lights with uncertain wattage for resin curing. Their wattages and advertised
wavelengths can vary considerably. Note that, for example, the advertised
wattage in inexpensive versions is often only the maximum possible wattage.
There are a number of things that affect the ability to reach this maximum,
from the LED to the structure of the flashlight (or other light source) used.