An extension infill is a procedure in which the grown-out area at the cuticle is filled with the same product, restoring the length and apex of the nail without removing the entire coating. It is most often done every 3–4 weeks: over that time the natural nail grows out, the thickest point of the extension moves forward, and the risk of breakage and lifting increases.
What is an extension infill and why is it essential
An extension is built so that its thickest point – the apex – sits at the stress area, where the nail separates from the nail bed. As the nail grows, the apex moves towards the free edge and the extension starts to act like a lever: every knock to the edge puts more strain on the base of the nail. This is how cracks and lifting at the cuticles appear.
Lifted product is not just an aesthetic issue. Moisture collects underneath it, creating a favourable environment for infections, which we cover in more detail in the article nail fungus after gel polish.
An infill differs from a new set in that well-adhered product is left in place and only the lifted and thinned areas are removed. This saves time, product and the natural nail.
How often to do an infill
The usual interval is 3–4 weeks. You may need an infill sooner if the nails grow quickly, the hands do a lot of work or the nails are long. It's time for an infill if:
- there is a clearly visible grown-out band between the cuticle and the coating;
- the coating has started to lift at the cuticles or sides;
- cracks have appeared or the nail catches on clothing.
If considerably more time has passed since the extensions were applied, it is often safer to remove everything and start again.
The infill process: filing down the grown-out area and filling it in
What you need for an infill
- E-file and bits: to thin the old coating and remove lifting, and gentler bits for work near the cuticles.
- Files and buffer: a coarser file for shaping the artificial coating, a finer one for the natural nail and smoothing the surface.
- Prep products: dehydrator, primer, lint-free wipes and cleanser.
- The same sculpting product the nails were built with, and a brush for it.
- A UV/LED lamp powerful enough to cure thicker layers of gel.
- A dust collector – a lot of filing is done during an infill, and neither the technician nor the client should breathe in fine dust.
Steps
- Assess the nails: lifting, cracks, colour changes under the coating. If you see signs of infection, do not carry out the infill.
- Shorten and shape the free edge.
- Remove the lifted product and thin the old coating with an e-file or hand file. It is especially important to create a smooth transition without a ledge from the edge of the coating to the grown-out area. Do not file the natural nail. We covered suitable e-file bits and speeds in the guide how to use an e-file for nails.
- Tidy the cuticles and remove the dust.
- Prepare the grown-out area: dehydrate it, and apply primer only to the natural nail.
- Fill in the grown-out area with a thin layer of gel and cure.
- Rebuild the apex with a second layer (described below), cure, shape the surface and finish with colour or top coat.
Use the same product for the infill as for the original extension. You will find builder gels in the gel system section. If you don't know what product the nails were extended with elsewhere, ask the client, or do the infill only after the old coating has been thinned to a thin, firmly adhered layer.
Repairing lifting and cracks
A lifted area must be removed completely – back to firmly adhered product. If new gel is simply applied over it, a gap remains under the coating where moisture collects, and the lifting returns within a few days.
File a cracked coating down to sound product and recover it with a new layer that covers the whole crack zone. If the natural nail itself has cracked, shorten it – a layer of coating will not reinforce such a crack.
If the same client's nails lift every time, look for the cause in the prep: leftover oils or cuticle tissue, too little or too much primer, gel on the cuticles. We described the differences between bonding products in the article primer, dehydrator and cleanser.
Rebuilding the apex
The apex is the thickest point of the extension, which absorbs the load. During an infill it is moved back to the stress area.
- Place a second, thicker bead of gel where the apex should be and let it self-level.
- Turn the client's hand with the nails facing down for a few seconds – the gel will gather at the apex. Then cure.
- Check the nail from the side – the curve should be even, with no hump near the cuticle – and from the front, where the C-curve should be the same on both sides.
- The coating should be thin at the cuticles and free edge, and thickest at the apex.
The most common infill mistakes
- A ledge at the cuticle. If the old coating isn't thinned smoothly, dirt collects on the ledge and the coating starts to lift.
- Filling too thickly. The nail becomes bulky and the apex shifts too close to the cuticle.
- Gel on the cuticles or sidewalls. Once cured on the skin, it lifts within a few days.
- Over-filing the natural nail. A thinned nail flexes, and the coating splits along with it.
- Leaving the apex in the old position. The infill then only hides the problem, and the nail keeps breaking.
When it's better to remove everything
- a large part of the coating has lifted on several nails;
- considerably more time has passed since application than the usual infill interval;
- colour changes are visible under the coating, the nail is sore or it has separated from the nail bed;
- the natural nail is very thin or damaged;
- you want to change the shape or length fundamentally.
If your nails need a rest, you will find tips in the article nail recovery after gel polish.
How to remove extensions safely
The method depends on the product. Builder (hard) gel does not dissolve – it is filed off with an e-file or hand file, leaving a thin protective layer on the natural nail, which later grows out. Acrylic and soak-off gels are softened with remover and gently pushed off. We described how the products differ in the article nail extensions: gel, acrylic or PolyGel.
At home, the safest way to remove soak-off products is by soaking, as described in the article how to remove gel polish safely. Hard gel is better left to a professional. Never peel or pry off extensions – layers of the natural nail come off with them.
FAQ
What is an extension infill?
It is a procedure in which the grown-out area at the cuticle is filled, lifting is removed and the apex of the nail is rebuilt without removing the entire coating.
How often should an infill be done?
Most often every 3–4 weeks. Sooner if the coating has started to lift or crack.
How does an infill differ from a new set?
During an infill, well-adhered product is left in place, whereas with a new set all the old coating is removed and the nail is sculpted from scratch.
How do I remove extensions at home?
Acrylic and soak-off gels – by soaking with remover under foil and gently pushing off. Hard gel has to be filed off, so it is better left to a professional. Never peel them off.