Hard Gel vs Builder in a Bottle – What’s the Difference ?

One of the questions I get asked and one i see on forums all the time is, “What’s the difference between hard gel and builder in a bottle?” And honestly, it’s a fab question – because while they’re both builder gels, how we use them and what they’re best suited for can vary quite a bit.

Let’s start with the basics. Both hard gel and builder in a bottle (BIAB) are classed as builder gels because we use them to add length, shape, and structure to the nail. That’s why they’re given the name “builder” – because they literally build or help build strength and structure.

Now here’s where it gets interesting. You’ll often hear soak-off gels referred to as soft gels and file-off gels as hard gels. And both types can actually come in either pots or bottles. Thanks to the popularity and convenience of soft gels in bottles, we’re now seeing more hard gels in bottles too – it’s all about making our jobs that little bit easier!

So what’s the real difference?

It mostly comes down to flexibility, strength, and texture.

• Soft builder gels (like Builder in a bottle) tend to be medium viscosity, meaning they’re not too runny and not too thick – just right for everyday strengthening and short extensions. Some soft gels can be a little thicker depending on the brand, but they’re still more flexible overall. 

• Hard gels are typically thicker and higher in viscosity, which actually makes them easier to work with when building up a structure or adding length. The thicker texture means they don’t run or level too quickly, giving you time to place and perfect the shape without it sliding into sidewalls or cuticle areas. That’s especially helpful when working on longer extensions or complex shapes.

Once you start to work with gel, the combination of brush movement, body heat, and room temperature can warm the product up. This warming process changes the viscosity, causing it to become looser and more self-levelling. This is a huge reason why builder in a bottle shouldn’t be applied in large beads, it simply doesn’t stay in place long enough to build a nice structure before it starts flowing into sidewalls and making a mess!

With Builder in a bottle/ soft gels, it’s best to apply in thinner layers, building up the foundation gradually before applying a final bead if needed. Rushing with large beads increases the risk of flooding, undercuring, and a wonky finish, and nobody wants that!

Removal – Soft vs Hard Gel

Soft builder gels are porous, which means that once you’ve filed the top layer down to the correct thinness, acetone can pass more easily, softening the product for safe removal.

That said, not all soft gels are equal. Some are so close in texture and strength to hard gel that, despite being classed as soakable, they’re still very tough to remove. In my experience, the higher the viscosity of the product, the harder it is to remove – and again, this comes down to the gel’s chemical composition, quality, and ingredient ratio.

Hard gels, on the other hand, are far denser and less porous, making it almost impossible for acetone to break them down in the same way. That’s why hard gel must be filed off completely, and this must be done with the right training to avoid damaging the natural nail plate. Without proper technique, it’s all too easy to cause trauma. Adding a thin soakable base to a hard gel can aide in removal ,once the hard gel has been filed away. You can simply soak the base off if you're worried about filing to far and damaging the natural nail with your file. 

Let’s talk about base coats

Now here’s something that often gets overlooked – base coat.

Some brands say their builder doesn’t need a base coat, and while that can be true, it doesn’t always mean you shouldn’t use one. Adding a super thin layer of base coat before applying your builder gel can make a world of difference.

This base layer acts as a flexible buffer between the natural nail plate and the more rigid builder product. It allows for a bit of natural movement and can really help prevent lifting, especially for clients prone to poor retention.

And of course, always make sure you’re using the base coat from the same brand as your builder gel. Gel systems are formulated to work together, and mixing brands can sometimes lead to performance or durability issues.

If lifting is something you struggle with, my free lifting lesson will really help you understand what’s going wrong and how to fix it, you can find it here .

And don’t forget – brand matters too!

Even within the same type of gel, viscosity, flexibility, and strength can vary hugely from brand to brand. That’s why I always encourage techs to really get to know their products and not just assume all builder gels are created equal. They’re absolutely not!

Unfortunately, many gel brands don’t have a strong understanding of the actual composition of their products, especially if they’re private-labelled or manufactured elsewhere and no compliancy measures are taken by the brand. So it’s always worth checking that they have a full and clear understanding of their product’s ingredients, behaviour, and how it’s intended to be used. If they can’t explain it confidently, that’s a red flag.

Knowing exactly what you’re working with helps you get better results – and more importantly, keeps your clients’ nails safe and healthy.

Knowledge is power ! 💪💅

Love Mel x