I wish people on here would stop being to rude to me, just because Im asking questions does not give you the right to be so nasty!
Nancy, so Gelish in it's make up has something that the led works with right to cure?
So with the Shellac what makes that lamp only work with Shellac?
Yes, Gelish has something different in its formula than Shellac that makes each of them work with different lights. And I think you have it reversed. It's not that the CND/Shellac lamp will cure only Shellac; it's that Shellac will cure (reliably, at least) only in a CND lamp.
You should read the Nails Magazine articles and Doug Schoon's technical articles for a better, fuller explanation but here goes... (And others, please chime in to supplement or correct me)
There are different photoinitators and they are defined by the wavelength of UV light they work with. There are photoinitiators that work with CFL UV and others that work with LED UV. Photoinitiators for gel polishes fall in the 320-400 nm spectrum. CFL UV lights (lamps mean the bulbs, lights mean the unit) emit a wide spectrum of light for a longer period and can cure a wide range. LED UV lights emit a much narrower range of light (usually around 370-380nm) but it is more intense. Because photoinitiators can cause sensitivity, Shellac has fewer and a different kind of photoinitators than other brands; it is why it claims to be hypoallergenic. But it can only cure in the CFL UV light. And because it has fewer photoinitiators, a thorough exposure and cure is especially critical.
Gelish, ACG, Geleration and others contain both kinds of photointiators so they can cure in either CFL UV or LED UV lights. In terms of lights, it is important to make sure that the light emits the proper concentration, energy and wavelength of UV light for that product, hence the insistence that you use the manufacturer's light with their product.