The way you prep for BIAB application shouldn’t make too much of a difference to your choice unless a brand requires rough treatment of the natural nail. But there were a few questions about prep steps so now is a good time to discuss them.

First, just to expand on what I mean by ‘rough treatment’ – in this day and age, with the technology available in the industry, there is NO, and I repeat, NO reason to prep the natural nail with an e-file or even with anything rougher than a 180-grit buffer (not file, buffer). There’s also no reason to use an acid-based primer, which was commonplace when adhesion technology wasn’t as good, but which chemically eats away at the nail to create a rough surface, potentially thinning the nail if overused or burning the client if used incorrectly. Acid-free primer, sure, just not acid itself.

Personally, I would stay away from any brand that instructs you to use something rougher than a 180-grit buffer or an acid-based primer on the natural nail as this tells me that their priorities are not with client safety and/or they don’t have access to high-quality ingredients.

With that out of the way, Kirsty asked – Why do some BIAB brands need primer beforehand yet others don’t?

The answer is all about that A-B scale from earlier in the module. The closer to the A End a BIAB is – indicated by thinner viscosity, decreased strength and increased flexibility – the looser the molecular structure is. Looser molecules are able to seep between the top-most layers of keratin cells and bond on their own.

When a product is closer to the B End, those molecules are getting tighter and tighter giving you thicker viscosity, better strength, decreased flexibility but worse adhesion. That worsened adhesion is because the molecular structure is bigger and therefore can’t fit into the same small gaps the thinner guys could. Since the BIAB itself can’t seep in and around the keratin cells, if we apply it straight to the nail, it will just sit on the surface. It will stick, but it won’t stick like a product that has been able to wrap itself around those first few layers like velcro.

This is where primer comes in – primer is thin and primer can seep in and wrap around the keratin cells for us. A small amount of primer sits on the surface of the nail and the BIAB bonds tightly to the primer. The ingredients in primer are attracted to and bond with both keratin and acrylate molecules, acting like a double-sided sticky tape (and called a double covalent bond).

With this, prep methods do actually play into your considerations when choosing a brand. If a brand requires a primer, it’s either got poor natural adhesive properties (this would be a cheap or knock-off brand) or (far more likely with reputable brands) the brand has prioritised strength in its formula. If a brand doesn’t require a primer, they have prioritised easy adhesion over strength. None of this means a primerless brand isn’t strong at all, because current technology generally allows us to have our cake and eat most of it too, but those priorities do matter.

Courtney had a question too, saying – “Most BIAB I’ve seen so far don’t seem to NEED a base coat, although some do. Why is this?”

The answer is pretty similar and ties in with Kirsty’s question and our considerations above. A base coat is a primer alternative. A brand that requires a base coat has put all their energy into priorities other than adhesion and is relying on the base coat for adhesion. This isn’t a bad thing – Artistic’s Correction Gel uses their Colour Gloss Bonding Gel base coat. The reason for this is that, well, Bonding Gel already existed. Correction Gel was seen as an add-on to a Gel Polish service. So why muck around creating a baseless BIAB when you’ve already got a perfectly good base? Most baseless BIABs still require you to paint and cure a thin layer first, which is no different than applying a base before your Correction Gel.

Essentially though, it’s all the same info – molecular structure informs how a BIAB adheres. A brand chooses to prioritise adhesion, flexibility, strength, ease of removal, viscosity and many other criteria when they’re in the development phase and until we’re at the point where we can have our cake and eat it plus the cherry on top, those priorities mean also choosing how their BIAB will adhere – on its own, with a primer or with a base.