ILNP Birefringence (H) is a very cool-toned, dark duochrome with a metallic finish. It is a permanent nail lacquer that retails for $12.50 and contains 0.4 oz.
ILNP Birefringence (H) Holographic Ultra Chrome Nail Polish ($12.50 for 0.4 oz.) has a black base with multichromatic shift that went between rich blue, deep violet, and warmer magenta. There was a hint of an olive gold at more extreme angles under sunlight, but it was predominantly blue-purple-magenta. This version of the shade included fine holographic micro-flakes throughout, which gave it a rainbow effect under bright light.
The consistency seemed slightly more fluid and a touch thicker compared to other multichrome shades I've tested out from the brand, so I felt like I had a little more product than desired on the second coat, but I was able to apply with the level of precision desired the second time I applied it. The first time, there were a few more visible brush lines from a normal viewing distance, but with the second application, I didn't have that issue. I'd also recommend giving it a little extra time to self-level and dry down, which also helped.
Per the brand, it has its maximum coverage in two coats. In the swatches, I've applied two coats and then one layer of Zoya Armor top coat (though I added Zoya Anchor as a base coat when I tested for longevity), which was all that was necessary for full coverage. I wore this shade for 10 days and had minor tip wear and no chips.
As a FYI, the brand offers this shade with and without holographic micro-flakes--shades designated with "(H") include the holographic micro-flakes.
FURTHER READING: Formula Overview, which is a detailed review of the range as a whole.
Butyl Acetate, Ethyl Acetate, Nitrocellulose, Adipic Acid / Neopentyl Glycol / Trimellitic Anhydride Copolymer, Acetyl Tributyl Citrate, Isopropyl Alcohol, Stearalkonium Bentonite, Acrylates Copolymer, Styrene / Acrylates Copolymer, Silica, Benzophenone-1, Trimethylpentanediyl Dibenzoate MAY CONTAIN Titanium Dioxide (CI 77891), Iron Oxides (CI 77489, CI 77491, CI 77492, CI 77499), Red 6 (CI 15850), Red 7 (CI 15850), Red 34 (CI 15880), Yellow 5 (CI 19140), Blue 27 (CI 75510), Black 2 (CI 77266), Mica, Aluminum Powder (CI 77000)
Disclaimer: Ingredient lists are as available by the brand (or retailer) at the time of publishing. Please always check product packaging, if it exists, for the ingredient list applicable to the product you're purchasing, or the brand or retailer's website for the most up-to-date ingredient list.