M42 is Mangrove Jacks' high-gravity yeast — chosen for beers that push beyond the limits of standard ale strains. Its very high alcohol tolerance and clean neutral profile make it the right choice for barleywines, imperial stouts, and double IPAs, where you need a yeast that ferments completely without stalling or producing harsh off-flavours under alcohol stress.

Best suited to: Barleywine, Imperial Stout, Double IPA, Triple IPA, Strong Ale, Wee Heavy, any beer targeting above 8% ABV.

Fermentation parameters:

• Temperature: 16–22°C (lower end for cleaner profile in high-gravity fermentations)
• Attenuation: High
• Flocculation: High
• Alcohol tolerance: 14%+ ABV
• Pitching rate: 2 sachets per 23L for beers above 1.080 OG; add yeast nutrient

Flavour contribution: Clean and neutral. At high alcohol levels, less robust yeasts produce harsh fusel alcohols — M42 minimises this and does not add competing flavour to complex malt profiles.

Choose M42 when your target OG is above 1.080 or target ABV is above 8%. Standard ale yeasts can stall or produce fusels in strong beers.

Pitching note: For very high-gravity beers above 1.100 OG, pitch 2 sachets, ensure yeast nutrient, and oxygenate well. Ferment at 16–18°C to minimise fusel production.

Storage: Keep refrigerated. Once opened, reseal and use within 7 days.