Vicfine is purified isinglass in convenient powder form. It is added to beer at the end of fermentation to speed maturation and improve filtration by removing yeasts and protein particles. For ease of use Vicfine in its standard form includes the necessary acid and preservative already blended.
The active component of Vicfine is isinglass (collagen). It is derived from the swim bladder of fish. Processing into finished form involves a regime of rigorous washing and sterilisation, followed by drying and milling. The precise nature of the action of collagen on yeast and proteins is not fully understood, and many suggestions have been promoted.