Sunday, May 5, 2013

Choosing a UV lamp to make gel nails

Every manufacture recommends that you buy their UV lamp, just as they also recommend that you only use their primer, bonder, etc. But is this because there are good reasons for this advice? Or, is it because the manufacturers simply want to make more money?

In this article I will explain why there are differences between various UV lamps, and I'll explain why CCFL and LED UV lamps are different from the traditional CFL UV lamp that you probably use right now. I'll also talk about the chemistry of gel nails and explain how all of these parts all fit together.  

It's all about the chemistry

Lets use the example of baking a cake. It's chemistry too. If you change the type of ingredients or the amount, or use too much or too little heat, then the cake won't taste like it should from the recipe. Remember that heat is just another form of energy which is used to make a chemical reaction, in the same way that we use UVA light to make a chemical reaction with nail gel. 

Fortunately, we can use ovens that are manufactured by different companies and still expect to bake a nice cake. 200 degrees C at 60 minutes exactly dictates the amount of energy required and will be the same amount of energy whatever brand of oven we use. If we are lucky enough to own a more expensive convection oven that uses a fan to distribute the heat, we know that type of oven is more efficient and we will need to use a shorter cooking time to get a good result. 

Unfortunately, creating a repeatable and good chemical reaction using UV gels and UV lamps is more complicated than baking a cake. That's because :
  • UV lamps are available that generate different amounts of energy
  • Different UV lamps and UV emitting devices have different levels of efficiency
  • Photoinitiators in gels and gel polishes require a specific wavelength and intensity of  UV light energy to work
So unlike the cooking example where 200 degrees at 60 minutes defined the correct amount of energy to bake the cake, if we use the wrong UV lamp to cure our gel then the result has four possibilities:
  • the gel doesn't cure. Not enough UV light is generated to cure the gel, or the generated UV light wavelength does not match the wavelength required by the gel or gel polish. 
  • the gel is not fully cured and may be soft near the nail plate. The nail enhancements will be weaker and will have less adhesion to the nail plate that can cause lifting problems. Uncured gel that touches the skin increases the risk of allergic reaction. 
  • the gel is cured perfectly to create the most reliable and best looking nails possible for that specific gel product
  • the gel is cured too much. Over curing increases the risk of excess heat that can cause the customer pain and product lifting that can cause bacteria to thrive. 

Photoinitiators - the crazy eggs in the UV gel cake

Photoinitiators are chemicals are added to gels to start the chemical reaction. When UV energy is applied in sufficient quantity, these photoinitiators break down to create free radicals that then attach themselves to the soft gel oligomers to create longer chains of the cured gel polymer. 

But like those strange eggs, different photo initiators require different levels of UV energy to break down and to make free radicals. Also, different photoinitiators need UV that has a particular UV light wavelength. So to create the most effective chemical reaction the photoinitiators and UV light source need to be compatible.

If you are confused by the word wavelength, it's the different wavelengths of light that make the colors of a rainbow, or make the light visible or invisible to the human eye. Next time you are at the beach, notice that some waves change slowly and have a longer wavelength, but as the sea approaches the beach the wavelength increases and produces those fast little waves before they break on the sand.

Why are different photoinitiators used?

Before gel polishes, nearly all hard and soak-off gels contained photoinitiators that required UVA light having a wavelength between 350 to 370 nm. A nanometer (nm) is a unit of length that is 1 meter divided by 1,000,000,000. 

As traditional UV lamps using Compact Florescent Light (CFL) light bulbs produce a range of light in the UV-A spectrum with wavelengths between 320nm to 400nm. Incidentally, the reason why we can see a purple light from our UV lamps is because it also produces light with wavelengths above 400nm that is within the light range visible to the human eye. What we can't see is are the UV wavelengths below 400nm that actually cures the gels. Take a look at the diagram below:

Image courtesy of NAILS magazine

So why do most gel polishes contain photoinitiators that need UV light with a wavelength of 390nm? 

The answer to this seems to be connected to the introduction of LED UV lamps. Light Emitting Diodes are semiconductor devices that are more rugged than glass bulbs. Also because they use less energy, work for up to 50,000 hours and don't contain mercury, they are kinder to the environment. 

But, until now it was only possible to buy LED's that created a peak of 405nm UVA at a low price. Although LED's exist that create UVA at a peak of 365 nm are available (and could be used to cure hard gels) - they are too expensive today to be used in UV nail lamps. So the gel polish manufacturers designed their product to work with the available LED UV lamps because these offered a shorter curing time of between 30 to 60 seconds, compared to the traditional CFL UV lamps that still need curing times from 120 to 180 seconds. 

What are LED UV lamps faster?

If you place your finger over the end of a water tap, the jet of water is much more intense than before because you have focused the water energy. It's the same idea with LED's. As these generate light over a much smaller range of wavelengths, the light intensity is greater than a traditional UV CFL lamp that blasts light across a much wider spectrum - much of it unused to cure the nail gel. So a 9W LED UV lamp, is going to cure gel polish much faster than a 9W CFL UV lamp. 

Less shine with LED?

Having tested a significant number of LED UV lamps and different gel polishes, we noticed that the top gel shine was worse on LED cured nails, than nails cured using CFL or CCFL UV lamps. 

CCFL UV lamps

CCFL or Cold Cathode Florescent Lamps are the new kid on the block. Like CFL UV lamps they use an excited gas to generate light inside a glass container. But like LED devices, CCFL have a long lifetime of between 30,000 to 50,000 hours. 

However they have one advantage over LED's; CCFL UV lamps generate UV light over a wide spectrum from 350nm to 400nm - so like CCL can be used to cure both hard gels and gel polishes. But CCFL UV lamps will not cure gel polishes as quickly as the best LED UV lamps. 

CCFL UV light bulbs are available in two shapes depending on UV lamp that is purchased. Notice that the UV lamp on the right also contains LED's:

UV Lamps - design is important

So far we've discussed the different devices that emit UV light, and how the UV wavelengths cures some or all gels and gel polishes. But let's now look at the two main factors that affect the performance of a UV lamp:
  1. the intensity of the UV light that is generated by the CFL, CCFL or LED devices
  2. the intensity of UV light that is produced on the nails

It's obvious that a 9W CFL UV lamp will produce less UVA intensity than a 36W UV lamp. But we also need to remember that 9W refers to the electrical power consumed, and is not a direct indication of the amount of UV produced. 

As with most things in life, you get what you pay for so a more expensive Philips or Sylvester CFL UV bulb is more efficient, maintains it's light output intensity and lasts longer than a low cost Chinese UV bulb. 

But the amount of UV light produced is not the only factor. It's also important how much of that light lands on the nail surface. The distance from the nail to the UV emitting device is important because distance reduces the UV intensity as it travels though air. Closer is therefore a better use of the UV created as more will be useful on the nail gel. 

Another factor that can be important is the quality of the reflectors inside the UV lamp. Both CFL and CCFL UV bulbs radiate light in 360 degrees so the reflectors are used to bounce as much UV light as possible onto the nail surface. 

With LED UV lights, reflectors are less important. That's because LED's project light in front of the device that is focus in a narrow area - like a spotlight. But if the LED's are only mounted on the top of the UV lamp, they are unlikely to cure gel on the the thumb nails. For this reason, higher quality LED UV lamps also have LED's mounted in the side walls. 


As we now understand, the UV lamp is an important part of the nail chemistry. For that reason, manufacturers recommend UV lamps that they have designed or tested to work with their gels. They want their gel customers to be produce reliable nails and avoid potential risks of salon customers developing allergies.

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