If you’re a nail tech, you’ve probably heard things like: “My gel is burning in the lamp – is it over-curing? My lamp is 80W, so surely it cures everything? The gel feels hard, so it must be cured."
Or even:“I’ll just cure it for another minute to make sure.”
But gel curing isn’t quite that simple.
You definitely don’t need to be a chemist to understand it, so let’s break it down in normal, everyday nail-tech language.
What Actually Happens When Gel Cures?
Gel contains ingredients called photoinitiators. I already covered this topic in our previous Nail Blog HERE
Think of photoinitiators as little light receivers inside your gel. When you put the gel into the lamp, the photoinitiators absorb light and start a chemical reaction called polymerisation.
Polymerisation is simply the process that changes your gel from its uncured state into the solid material we wear on the nail.
But here’s the important part: Just because a gel feels hard on top doesn’t automatically mean it has cured properly all the way through.
What Is Under-Curing?
Under-curing simply means the gel hasn’t received what it needs to achieve an adequate cure.
There are lots of reasons this can happen.
You might be using the wrong lamp for that particular product.
Your curing time might be too short.
The product might be applied too thick.
The client’s hand might be positioned incorrectly.
The thumb might not be receiving enough light.
A highly pigmented colour might have been applied too thick.
The quality of the gel, ingredients and photiniciators.
Or the light produced by your lamp might not be a good match for the photoinitiator system inside your gel.
You can’t always see under-curing.
The top of your gel can feel completely hard while the product underneath hasn’t cured sufficiently.
That’s why touching the surface isn’t a reliable curing test.
Why Is Under-Cured Gel a Problem?
When gel polymerises, reactive ingredients are being incorporated into the polymer network. If the product doesn’t cure adequately, more unreacted material can remain within the coating.
Apart from potentially affecting the performance and durability of the product, we particularly don’t want uncured or inadequately cured gel coming into contact with the client’s skin. This may lead to potential allergic reaction. This is one of the reasons correct curing is such an important part of professional gel services.
So Why Do Some Gels BURN in the Lamp?
Now let’s talk about something nearly every nail tech has experienced.
🔥 HEAT SPIKES.
Your client suddenly pulls her hand out of the lamp and says: “OMG, IT’S BURNING!”
Why does one gel feel completely fine while another gets really hot?
The first thing to understand the lamp isn’t necessarily heating the gel like an oven. The heat is largely being created by the curing reaction itself. Polymerisation produces heat. We call this an exothermic reaction.
Basically:
Gel starts curing → chemical reaction happens → heat is released.
And if lots of that reaction happens very quickly, your client can feel a sudden burst of heat. This is the reason why you shoud use the lamp with low heat mode with certain types of gels where the polymerisation happens fast.
That’s the heat spike.
Why Do Some Gels Heat Up More Than Others?
There isn’t one simple answer because lots of things can affect it.
The formulation itself matters. But the amount of gel matters too.
Think about the difference between a very thin base coat and a big builder gel apex.
With the apex, you’ve got much more product curing in one place.
More material is going through polymerisation, which means more heat can be generated in that area.
That’s why heat spikes are particularly common with builder and hard gels.
The client’s nails matter too.
A client with healthy, thicker natural nails may barely feel anything.
A client with very thin, damaged or over-filed nails may feel the same curing reaction much more strongly.
So remember:
Heat spike does NOT mean over-curing.
It usually means your client is feeling heat produced during polymerisation.
So What Does Low Heat Mode Actually Do?
Low Heat Mode isn’t there because normal mode is “too hot”.
It simply changes how quickly the curing reaction gets going. Instead of immediately delivering the lamp’s full intensity, a well-designed low heat programme gradually increases the output.
Instead of encouraging a huge amount of reaction to happen very quickly, we slow down the beginning of the process. The gel still needs to cure properly – we’re simply trying to make that initial reaction more comfortable for the client.
What About Over-Curing?
This is probably one of the most misunderstood terms in the nail industry.
People often imagine curing like this:
30 seconds = under-cured
60 seconds = perfectly cured
90 seconds = OVER-CURED
It doesn’t work quite like that.
If a manufacturer recommends curing for 60 seconds, leaving the hand inside for a few extra seconds doesn’t suddenly destroy the gel. Polymerisation progresses toward the level of conversion that the particular gel formulation and curing conditions can achieve.
Follow the recommended curing time for the product you’re using.
More time isn’t automatically better.
“But My Lamp Is 80W…”
Here comes another huge nail-industry misconception.
Higher wattage does NOT automatically mean better curing.
You can have two lamps that both say 80W and they can perform very differently.
Wattage alone doesn’t tell us how much useful curing light is actually reaching the gel.
There are other things we need to consider.
Wavelength
Your gel contains photoinitiators. Those photoinitiators respond to particular types – or wavelengths – of light. You’ll often see numbers such as: 365–405 nm on modern nail lamps.
Without getting too scientific, those numbers describe wavelengths of light.
Think about it like this:
Your lamp is sending a message.
Your photoinitiators need to understand that message.
Lamp and photoinitiators need to speak the same language.
A super powerful lamp isn’t much use if its light isn’t suitable for the photoinitiator system you’re trying to activate.
What Is Irradiance?
Irradiance basically tells us how much light power is reaching a certain area.
It’s commonly measured in: mW/cm² – milliwatts per square centimetre.
You don’t need to remember the unit.
What matters is understanding the idea.
Imagine having a really bright light. If that light is distributed badly, one nail might receive lots of light while another receives much less. That’s why a huge wattage number on the outside of the lamp doesn’t tell us the full story. We care about how much useful light actually reaches the gel.
And What Does “Output” Mean?
You’ll also hear people talking about lamp output. Very simply, we’re interested in the useful light the lamp is actually producing and delivering inside the curing area.
We want to know things like:
Does it produce suitable wavelengths?
Is enough light reaching the nails?
Is the output consistent?
Does the thumb receive good exposure?
Do the sides of the nails receive enough light?
Is the light distributed evenly?
That’s why lamp design matters so much.
Why Does LED Positioning Matter?
Look at your hand. Your nails don’t all point in exactly the same direction. And your thumb is the obvious troublemaker. 😂 It naturally sits sideways.
So imagine a lamp where most LEDs are simply positioned directly above the four fingers. You could have incredibly powerful LEDs, but that doesn’t necessarily mean the thumb and sides of the nails are receiving the same exposure. That’s why good lamp design considers where the hand actually sits inside the lamp. Same applies to the top par of the lamp and bulb coverage - in a simple wording everyone has different length of fingers and we need to make sure the whole surface is covered. LED positioning, LED angles and the design of the curing chamber all matter. A reflective interior can also help redirect light around the inside of the lamp. It’s all about where they are and how effectively their light reaches the nails.
What About Photoinitiators?
Photoinitiators absorb suitable light and start polymerisation.
Some gels use a combination of different photoinitiators. And that can be useful because different photoinitiators can absorb different parts of the light spectrum and have different purposes in gel formulation - some are designed to cure bottom layers some top layers and others are responsible for proper structural curing through the whole nail.
More photoinitiator does NOT automatically mean better BUT...
What we want is a well-designed combination of photoinitiators appropriate for that particular formulation and curing system.
It’s about formulation and compatibility.
So What Actually Makes a GOOD Nail Lamp?
Now we can put everything together.
A good professional lamp isn’t simply:
❌ Highest wattage
❌ Most LEDs
❌ Most expensive
❌ Brightest-looking light
We want several things working together.
Suitable wavelengths- The lamp needs to produce light that works with the photoinitiator systems in the gels it’s intended to cure.
Good irradiance- Enough useful light needs to reach the product.
Even light distribution- We don’t just want loads of light hitting the middle finger while the thumb receives much less.
Good LED positioning- The LEDs need to be positioned so that light can reach all five nails effectively.
Consistent output- A professional lamp needs to perform consistently rather than delivering unpredictable results.
Good internal design- The curing chamber, LED angles and reflective surfaces can all contribute to how effectively light reaches the nails.
But there’s something else that’s incredibly important.
TESTING.
A brand shouldn’t simply choose a lamp from a catalogue, see that the gel feels hard after 60 seconds and say: “Perfect! It works.”
Because remember:
HARD doesn't automatically mean PROPERLY CURED.
Ideally, the lamp and products should be evaluated together as a curing system.
That means looking at how the intended products perform in that lamp using appropriate application thicknesses and curing times.
This becomes particularly important with products that can be more challenging for light penetration, such as highly pigmented colours or thicker builder/hard gel applications.
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