The Sticky Layer on Gel: What It Really Means and Why No-Wipe Does Not Automatically Mean Hard

When choosing a material, we look at color, coverage, viscosity, strength or flexibility. But what about the sticky layer?

This article was actually inspired by a very simple customer question: whether we have a white gel that leaves a sticky layer after curing.

Of course we do. But while answering, another question came to mind: Why do we sometimes want a sticky layer and at other times look specifically for a no-wipe product? Is a no-wipe product only meant to save us work, for example with a final gloss? Does it perhaps mean better coverage? And why, then, do no-wipe color gels, French gels or nail-art gels exist?

And most importantly: what does the information “with a sticky layer” or “without a sticky layer” really tell us about the properties of the material?

After more than twenty years of working with UV/LED materials, I have found that some of the rules we learned in the past still make practical sense. Their explanation, however, is not always as simple as we once thought.

What exactly is the sticky layer?

After polymerization, some UV/LED materials leave a tacky layer on the surface, commonly referred to as the sticky layer, dispersion layer or inhibition layer.

Its formation is related, among other things, to the effect of oxygen on free-radical polymerization. At the surface of the material, where it is in contact with air, oxygen partially inhibits polymerization. As a result, the surface may not reach the same degree of conversion as the material underneath.

In some products, the sticky layer is very noticeable; in others, it is almost imperceptible; and some products are formulated as no-wipe.

Having a sticky layer does not mean worse. Being no-wipe does not mean better.

They are simply different properties of specific gels. What matters most is what we need the product to do.

No-wipe = hard? This is where I stopped and reconsidered

For many years, I also associated no-wipe materials with a harder, sometimes almost “glass-like” surface. And I used to say so.

There were not many of them. In our range, for example, there was Quick Finish and the Perfect Line series of color gels.

I was only partly right.

I still observe this behavior in some products today. But all it took was to take a few newer materials, cure them in the same thin layer and start comparing them.

And the simple rule fell apart.

For example, Quick Finish 1408 cracks when bent after curing in a thin layer. The newer no-wipe Brilliant Gloss 1484, on the other hand, behaves significantly more flexibly in the same simple test.

Both are no-wipe.

From practice, we knew that Quick Finish could sometimes crack when used as the final layer over a more flexible enhancement. On a rigid enhancement, however, it performed beautifully. We had similar experiences years ago with the Perfect Line range.

The comparison between newer no-wipe Cat Eye and Reflective gel polishes is just as interesting. One may remain relatively flexible after polymerization, while another may be noticeably more brittle in a thin layer.

No-wipe therefore no longer automatically means hard.

The presence or absence of a sticky layer alone does not tell us whether the final material will be hard, soft, rigid or flexible.

The mechanical properties of the cured product result from its full formulation, the ratio of the individual components, the structure of the polymer network created, the degree of cross-linking, the photoinitiator system, pigments or other fillers, and of course correct polymerization.

That is why today I would not automatically attribute the differences between Cat Eye, Reflective or Basic gel polishes to magnetic pigment, glitter or any single ingredient. Without knowing the full formulation, I would only be guessing.

The information “no-wipe” alone is therefore not enough to assess the mechanical properties of a material.

Quick Finish Natur: an example that taught me a lot

We have a very good example directly from DENATO practice.

Because of legislative changes, we had to replace our popular Quick Finish Natur, which many of you may remember.

The original product, like Quick Finish, was hard, no-wipe and had one property we loved for nail art: pigments could be buffed into its surface to an almost mirror-like effect, even several days later.

Of course, we wanted to have the closest possible replacement made.

But during reformulation, while also trying to preserve the no-wipe character of the product, it was no longer possible to simply create an identical material with all the original properties.

We do have the new product. It works excellently as a no-wipe gloss and in some properties we even prefer it.

However, pigment can no longer be buffed into it in exactly the same way as into the original Quick Finish Natur.

And this is a perfect example of how complex the formulation of a UV/LED material really is.

Changing a raw material or a photoinitiator system does not simply mean “we remove one substance and replace it with another”.

The resulting formulation has to work again as a complete system:

• polymerize in the intended lamp and curing time,
• create the required surface,
• have the correct hardness or flexibility,
• maintain the desired shine,
• provide suitable adhesion,
• and meet other required performance properties.

Two products can therefore both be described as “no-wipe”, yet their surfaces may behave so differently after curing that a nail-art technique that works perfectly on one will not work on the other.

So does the sticky layer actually have a function?

This brings me to a rule that nail technicians who started around the same time as I did may remember:

“Gel sticks to the sticky layer or to a roughened surface.”

This is what we were taught more than twenty years ago, and in practice the rule worked.

Today, however, I would be more careful with the word “only”.

The sticky layer does not primarily form in order to “glue” individual gel layers together. It is mainly a consequence of oxygen inhibition of polymerization at the surface of the material.

During curing of a UV/LED material, the photoinitiators start the polymerization reaction when exposed to light. At the very surface, however, the material is in contact with oxygen from the air, which partially suppresses free-radical polymerization.

The result may be the familiar tacky surface layer, also called the inhibition or dispersion layer.

The sticky layer is therefore not a sign that the lamp “did not reach” the surface, nor is it automatically a sign of insufficient curing.

For a product formulated to leave a sticky layer, this is an expected result of polymerization.

Most builder gels leave a sticky layer, as do many bases and color gels.

And over time, we learned how to use this property in our work.

Is the sticky layer a “glue” between individual layers?

We often hear the comparison that the sticky layer works like double-sided adhesive tape between individual gel layers.

It is an easy image to understand in practice, but chemically the reality is more complex.

With compatible light-cured materials, the sticky layer can support contact and bonding with the next layer.

That does not mean, however, that two polymer layers cannot bond without it.

The sticky layer is therefore not the only condition for interlayer adhesion.

If it were, why would material adhere to a correctly roughened surface?

The sticky layer can support the bonding of compatible layers, but it is not the only mechanism by which individual layers adhere to one another.

This is also why there is usually no need to automatically remove the sticky layer between individual steps of an enhancement unless the application system specifically requires it.

At the same time, the opposite statement is also not true:

No sticky layer does not mean the next layer will not adhere.

When working on a smooth no-wipe surface, I follow the manufacturer’s recommendations and the compatibility of the specific materials.

If the system requires mechanical roughening before the next application, I use a buffer or a fine file.

The absence of a sticky layer alone is not proof that the next layer cannot adhere.

With builder material, there is therefore usually no reason to remove the sticky layer between layers unless the application protocol requires it.

With color gels, the situation may be different, for example when I need to prepare the surface for further painting or a specific nail-art technique.

And what about no-wipe materials?

No-wipe products are formulated so that, after correct polymerization, the usual tacky surface layer does not remain.

How this result is achieved depends on the specific composition of the material.

And that brings me back to my own tests.

If I take two no-wipe products, cure them in a similarly thin layer and one cracks when bent while the other flexes, it becomes very clear that the information “no-wipe” alone tells us nothing about the hardness or flexibility of the material.

Does no-wipe mean we can apply the gel as thickly as we want?

No.

And here it is important to separate two different things.

No-wipe tells us something about the final surface of the material, not about the recommended thickness of application.

With light-cured materials, we are dealing with two opposite challenges.

At the surface, there is oxygen, which can inhibit polymerization. This is particularly relevant in very thin layers exposed to air.

Deeper in the material, however, the issue is light penetration.

Photopolymerization in depth is limited by light absorption, which means that a thick layer may reach a different degree of conversion at the surface than inside.

This is why one practical rule makes a lot of sense to me today:

I would not start using a no-wipe color or nail-art gel that the manufacturer designed for thin application as a builder material just because I like its consistency, color or hardness.

Not because it has no sticky layer.

But because its formulation and photoinitiator system may have been designed for a specific application thickness.

This is even more important with pigmented products, because pigments and other components can affect light penetration and polymerization.

In general, the type and concentration of the photoinitiator, the intensity and wavelength of the light, viscosity and other formulation parameters are important factors in polymerization.

UV/LED light must penetrate the entire applied layer and activate the photoinitiator system sufficiently even in its depth.

The thicker the layer and the more its composition absorbs or scatters light, for example because of pigments or other fillers, the more the specific formulation, lamp and curing technology matter.

A dry surface does not mean the entire layer is correctly cured

I therefore would not apply a no-wipe color or nail-art gel intended for thin application in a thick layer just because the surface looks perfectly hard and cured immediately after coming out of the lamp.

Of course, I also learned this in practice.

When working with sample tips, I once failed to control the layer thickness because I wanted to finish the samples more quickly.

Not immediately, but after some time, the gel layer inside the tip began to wrinkle, even though it looked perfectly fine right after finishing.

This is exactly where I see a major risk in trying to apply gel polish in one thicker layer.

It can happen with a product that leaves a sticky layer just as easily as with a no-wipe product.

That is why I recommend applying gel polish in thin layers and following the manufacturer’s application protocol.

Coverage and layer thickness are not the same thing

I understand that high coverage is in great demand today.

But coverage and layer thickness are not the same thing.

The development of UV/LED materials is moving forward very quickly. In recent years, it has also been strongly influenced by changes in European legislation and the resulting reformulations.

Manufacturers are looking for new combinations of raw materials and photoinitiator systems while trying to preserve the properties we expect from modern products:

• good coverage,
• comfortable application,
• shade stability,
• reliable polymerization.

The fact that a modern gel polish can provide beautiful coverage in the first thin layer does not mean that we can replace two thin layers with one thick one.

During polymerization, the light must penetrate the material sufficiently.

With a thicker layer, especially with highly pigmented shades, light penetration into the depth may be limited.

The surface may feel firm and, with a no-wipe product, may even look completely dry without this appearance alone confirming that the entire thickness of the material has been correctly polymerized.

“But the first layer already covered perfectly” is not a reason to apply it more thickly.

Coverage tells us something about the optical properties of the product. It does not tell us that we may apply it in a thicker layer.

Perhaps, paradoxically, the better the materials we have available, the more important it becomes not to confuse their improved user properties with permission to ignore the application technology.

A no-wipe surface can be a little deceptive

With a product that leaves a sticky layer, we expect the surface to remain tacky.

With a no-wipe product, we get a beautiful, smooth and often glossy surface that can easily make us feel that everything has cured perfectly.

But the surface alone does not tell us what happened throughout the full depth of the material.

A dry surface is therefore not proof of correct polymerization through the entire layer.

I should also mention one older practical experience.

Although the sticky layer is not usually removed from classic color gels between layers, I also used to wipe it off occasionally, for example when I wanted to continue painting.

And by doing so, I sometimes discovered that the color layer had not been cured sufficiently.

In that case, the only option was to correct the mistake.

But the sticky layer can sometimes be troublesome too

A pronounced and relatively fluid sticky layer can affect the behavior of the next color layer.

During application, we may notice a different distribution of pigment or an apparent “thinning” of the next layer.

This can happen with color gels as well as with thin-layer gloss products.

Likewise, it is not a good universal rule to wipe off the sticky layer every time we see it.

By wiping it off, we change the surface onto which we are going to apply the next material.

So instead of automatically asking “wipe or do not wipe?”, I would always ask:

What is going on top of this layer next?

The situation is different before another structural or color layer than it is after the final gloss.

And in nail art? There, the sticky layer can be very useful

We do not have to see the tacky surface layer only as something that needs to be removed.

In nail art, we can use it intentionally, for example for:

• certain transfer foils,
• fine glitter,
• pigments,
• other effects.

At other times, we want exactly the opposite.

No-wipe materials are practical for techniques where we need a dry, smooth and clearly defined surface after curing, for example for certain lines, ornaments, chrome effects or layered nail-art designs.

So once again:

It is not about whether the sticky layer is good or bad. It is about what we are trying to create.

And what about our old rule: “let the sticky layer cool down”?

Anyone who has worked with gels for a long time may remember the recommendation to wait for a moment after taking the hand out of the lamp and only then remove the sticky layer from the final gloss.

We used to do this with certain gloss products that left a sticky layer, and many nail technicians still follow this procedure today.

But does the sticky layer itself really “cool down” in a way that matters?

Today, I would be more careful with that explanation.

Of course the surface cools down after leaving the lamp. The question is whether cooling of the sticky layer itself is really the cause of what we observe in practice.

It is not accurate to simply say that the sticky layer needs to “cool down”.

It is more likely a technological procedure related to the specific properties of the product and the condition of the surface immediately after polymerization.

That is why the manufacturer’s recommended procedure for the specific product should take priority over a general rule.

With our Brilliant Glanz Exclusive, one of our long-standing gloss products with a sticky layer, for example, we recommend this procedure based on practical experience.

It is similar with transfer foils

We have a similar experience when transferring foil directly onto the sticky layer.

If we apply it shortly after polymerization, the transfer is usually very good.

If we leave the surface standing for longer, the foil may transfer much less effectively.

In practice, we often used to say that the sticky layer “cools down”.

But here too, it is useful to separate our long-standing practical observation from the chemical explanation.

The fact that surface properties change over time after polymerization does not automatically mean that cooling of the sticky layer is the only cause.

The final effect may be related to the condition and composition of the surface layer, ongoing processes after the light exposure has ended, the temperature of the material and other properties of the specific formulation.

For us, the practical conclusion is simple:

If we want to use the sticky layer for foil transfer, we work with it at the time and in the way recommended for the specific material.

It is another beautiful example of how we learned in practice what works long before we ever needed to know why it works.

So what can we actually learn from the sticky layer?

Above all, I would not use it to judge:

• product quality,
• hardness,
• flexibility,
• coverage,
• or overall mechanical resistance.

When choosing a material, I would start somewhere completely different:

• What do I need from the material?
• Am I building structure?
• Am I strengthening the natural nail?
• Am I applying color?
• Am I painting fine lines?
• Do I want to use foil, pigment or chrome?
• Do I need another layer afterward?
• Or is this already the final surface?

Only then does the information about the sticky layer become truly useful.

What should we take from this into salon practice?

• No-wipe does not automatically mean hard or brittle.
• A sticky layer is not automatically a sign of poor curing.
• The sticky layer is not the only mechanism responsible for adhesion between layers.
• No-wipe says nothing about how thickly the product may be applied.
• Coverage and layer thickness are not the same thing.
• A dry no-wipe surface does not confirm correct polymerization throughout the entire layer.
• The sticky layer can be both a disadvantage and a very useful tool in nail art.
• The manufacturer’s application protocol for the specific material always takes priority.

FAQ: Common questions about the sticky layer

Is the sticky layer a sign that the gel is poorly cured?

Not automatically. In a material formulated to leave a sticky layer, the tacky inhibition layer is an expected surface property after polymerization.

Do I always have to remove the sticky layer between layers?

No. If the application system does not specifically require it, the sticky layer is not normally removed automatically between individual layers of an enhancement.

Is a no-wipe gel harder than a gel with a sticky layer?

Not necessarily. Two no-wipe products can have very different hardness, flexibility and brittleness after curing.

Can I apply a no-wipe color gel in a thicker layer?

The fact that a product is no-wipe says nothing about the recommended application thickness. If the product is intended for a thin layer, that application protocol should be followed.

Why does foil sometimes transfer better onto a fresh sticky layer?

From practice, we know that surface properties may change over time after polymerization. That is why, when working with foil, it is best to follow the specific procedure recommended for the material being used.

Summary: the sticky layer is only one piece of information about the material

Even after more than twenty years of working with UV/LED materials, I can take two products, say that both are “no-wipe”, cure them side by side and find that one cracks when bent while the other flexes.

The sticky layer is therefore only one piece of information about the material.

It is not a guide to how the material as a whole will behave.

That is why it is not enough to choose a gel based on a single property.

What matters more is knowing what we expect from the material, what it was formulated for and which application protocol the manufacturer recommends.

Article author

This article was prepared by Lucie Králová and the DENATO expert team based on more than twenty years of experience with UV/LED materials and professional salon practice.

Updated

This article has been updated in line with current knowledge and professional practices in the field of nail enhancement.