Permeability and Breathability
Halal nail polish consists of an open lacquer basket. It is developed on the basis of a chemical formula with thermoplastic polymer which, in conjunction with other auxiliaries and chemical reactions, penetrates and punctures the paint – or rather enters and creates amorphous regions: There are microscopic trails in the paint that allow the water particles to penetrate and rest on the nail belt:
Thermoplastic polymers create amorphous regions in the paint. Polyolefin plastomer (POP) is, for example, a polymer composed of l-Bute and 1-ocetane molecular bonds. This polymer is used in plastic packaging to create breathability.
POP is assisted by polyethyn (PE) which distributes the molecular weight in the chain to prevent the holes from pulling together.
In contrast to the permeable nail polish, the conventional nail varnish is dominated by crystalline polymers which form dense layers in the structure, which makes it impossible for the water particles to penetrate. The illustration below gives a visual insight
In relation to the permeable nail polish, it is important to understand that the argument about halal is based on porosity. The permeable nail polish does not lay like a tight nail on the nail. It is porous, which means that the paint contains microscopic openings and passages that allow the water vapor to pass through the paint and moisten the nail belt.
In fiqh al-tahara (purity ethics before prayer) thoroughness and water treatment are two important criteria for the validity of wudu. The issue of nail polish, as an impermeable barrier to water, has therefore been pointed out in the English translation of the hanafi manual Nur al-Idah (The Ligth of Clarification). Based on the principle qiyas (analogy), the translator of Nur al-Idah, Wesam Charkawi, compares nail polish with wax and greasy substances (such as body oil). These are mentioned in the original Nur al-Idah script of Hasan Shurunbulali (f.1580). In the conditions that validate wudu , Shurunbulali mentions that waxes and greasy substances void wudu.
The Messenger of Allah (ﷺ) said: When the believing servant does wudu and he (or she) rinses his mouth, the wrong actions leave it. If he cleans his nose, the wrong actions leave it. As he washes his face, the wrong actions leave it, even underneath his eyelashes. If he washes his hands the wrong actions leave them, even underneath his fingernails. If he wipes his head, the wrong actions leave it, even from his ears. And as he washes his feet the wrong actions leave them, even from underneath the toenails of both his feet.
(Source: Al-Muwatta or Imam Malik Ibn Anas, Chapter on Purity, 2.6: 31 translated by Bewley 2001, 13).