Flax gives both linen fibre and seed holding 35-45% oil, but linseed oil spoils fast: it keeps only about 1-3 months and is best used as a drying oil for wood finish, waterproofing and paint rather than as a staple food oil. An acre yields 400-800 lb of seed and about 70-252 lb of oil after pressing at 50-70% recovery.
Part of Oil Pressing at Scale
Flax grown for seed oil: what the oil is good for, why it spoils so fast, what an acre yields, and the fire hazard of oil-soaked cloth.
Linseed Is An Industrial Oil First
The carrier calls flax dual-purpose: linseed oil for wood treatment, waterproofing and paint (it is a drying oil), and flax fibre for linen. It also notes that raw linseed oil has a strong flavour and goes rancid quickly, and is best used industrially unless fresh-pressed and eaten immediately. Its shelf life in the carrier’s list is the shortest of the oils: 1-3 months, against 6-12 months for sunflower and 12-18 for olive.
A drying oil hardens in air into a waterproof film, which is what makes it a finish for wood, a waterproofing for cloth and cord, and a paint vehicle (Oil Extraction).
What The Acre Yields
The carrier gives 400-800 lb of seed per acre at 35-45% oil. In the seed that is 400 x 0.35 = 140 lb up to 800 x 0.45 = 360 lb. Pressed at 50-70%: 400 x 0.35 x 0.50 = 70 lb and 800 x 0.45 x 0.70 = 252 lb, which at 7.68 lb per US gallon is 9 to 33 gallons. Flax is the lowest-yielding of the field oil crops here; grow it for the finish and paint oil and the linen, not as the village’s cooking oil.
Fibre Or Seed Is A Compromise
Fibre flax is pulled before the seed is fully ripe, so a crop grown for the best linen gives less seed (Flax Processing), which is a general fact recalled here and not a corpus figure. Decide the main purpose before sowing: a patch for fibre, a separate patch for seed.
What You Need
- A seed patch, separate from the fibre patch
- A press and a way to clean small seed (Screw Press Design)
- Small, dark, full containers, because the oil spoils quickly (Rancidity Prevention)
Method: Using The Oil
Step 1: Press and settle the oil as for other seeds.
Step 2: Store in small, full, dark jars in a cool place and use within 1-3 months.
Step 3: Use it as a finish. Rub thin coats into wood and let each dry fully before the next; soak cloth or cord for waterproofing.
Step 4: Dispose of oily rags safely (see the danger block).
Common Mistakes
- Making a year’s linseed oil in one go. It spoils in 1-3 months.
- Eating old linseed oil. Rancid oil smells sharp or like paint; use it for finish, soap or lamps.
- Feeding the cake like sunflower meal. Flax meal contains cyanogenic glycosides and should be fed in limited quantities (Meal and Cake Utilization).
Oil-soaked rags can ignite on their own
Cloth soaked in a drying oil such as linseed oil heats as the oil dries and can burst into flame without any spark (a well-known hazard, recalled here). Lay used rags flat outdoors to dry, or soak them in water in a closed metal can before disposal, and never pile them or leave them in a heap inside. Keep open flame away from the oil and the rags.
What’s Next
- Learn next: Screw Press Design - how the oil is pressed
- Combine with: Plant Oils - drying oils and soap