The graph (supplied by Doug Schoon) shows the UV light output from a traditional UV lamp and a LED UV lamp. Notice the peaks in UV irradiance at different light wavelengths.
UV irradiance is if you like, the amount of light energy (Watts) that falls on a 1cm x 1cm area. From this we can understand the amount to UV energy that falls onto a finger nail.
The amount of the irradiance is controlled by different factors: the type of UV light device used (different devices from different manufacturers output more or less UV energy), the distance from light device to finger nails, the quality of the lamp reflectors, etc. So depending on which UV lamp is being tested, these peaks will change in height.
The position of these peaks on the wavelength axis can also change depending on the light device. In this example the traditional UV lamp seems to have a peak at 370 nanometers - but another UV lamp could have it's peak at 360nm or 365nm, etc. Same with the LED UV lamp.
If you tested 10 different UV lamps the size of the peaks and the peak wavelength would all be different. This is a very important point.
Now, if we take the UV lamp used for this graph that has a peak at 370nm, and we try to cure a gel that has a photo initiator which operates best at 370nm then both the gel and UV lamp are matched and you will obtain the fastest cure time. But if you use a gel that has a 360nm photo initiator this is going to get approx 80% less UV energy and that would increase the cure time by at least 4 times (it also depends on how much PI is in the gel).
The problem is that the NT who uses the wrong gel for this UV lamp may not know that the gel is under cured. That's because gels appear hard when only cured at 50% of full cure. It's not possible for the average NT to know if a gel is fully cured without scientific equipment.
Different gels use different photo initiators and may have more or less of this. There is no standard, just like there is no standard UV lamp design.
This means that the gel chemist has to either:
a) design the gel to match a UV lamp that the company already has, or
b) design a UV lamp to match their new gel.
But the fact is that most manufacturers, even some famous brands, are not developing their own gels. They buy standard products from the catalog of one of the acrylic / gel factories - in other words they are private labellers and not real manufacturers.
In most cases they are never told, and don't know to ask, what photointiator is used in the gel and what amount of UV energy is needed to correctly cure the gel (and the curing time). That makes it impossible for them to find a matching UV lamp.
This begs the question of how a private labeller can know that their UV lamp will cure the factory gel, especially when they don't have a laboratory with the required test equipment and a chemist to make the tests. Perhaps some hire an outside laboratory to make the test, but I suspect that many of them stick a glob of gel on a tip, cure it for 2 minutes and see if it looks hard - which as you know now is no kind accurate test.
So when a supplier says that their UV lamp will cure all gels, ask them how they know what the peak UV irradiance and the peak wavelength required by the photo initiator in your gel is. Without that information, how can they possibly say that their UV lamp will cure your gel?
