Seed Pressing

Part of Food Processing

Three progressively better press designs — mortar, lever, and screw — that extract oil from seeds and nuts using mechanical advantage.

Why Press Design Matters

You can extract some oil by simply squeezing a handful of crushed nuts in cloth. But “some” is not enough. A good press multiplies your force by 10-50x, extracting 60-70% of available oil instead of 20-30%. The difference is measured in liters of oil per season — liters that mean cooking fuel, lamp light, waterproofing, and soap. Building a better press is one of the highest-return investments of labor in a post-collapse settlement.

This article covers three designs in order of increasing complexity and output. Start with what you can build today and upgrade as your toolmaking capability grows.

Method 1: Mortar and Pestle Press

The simplest “press” is not a press at all — it is brute-force crushing that releases oil directly.

How It Works

Pounding oily seeds in a stone mortar ruptures cell walls. Oil pools at the bottom. You periodically tilt the mortar to pour off accumulated oil, then resume pounding. Heat from friction and from warming the mortar over a fire increases oil release.

Construction

No construction needed — use any concave stone (mortar) and heavy rounded stone (pestle) available. A hardwood mortar carved from a log section works equally well. The mortar should be at least 15 cm deep and 20 cm across.

Operation

1. Roast and coarsely crush seeds per Oil Extraction steps.
2. Add a handful of crushed seeds to the mortar.
3. Pound vigorously for 5-10 minutes. Rotate between straight downward strikes and circular grinding motions.
4. The paste becomes visibly oily. Tilt the mortar over a collection vessel and press the paste against the wall with the pestle to squeeze out pooled oil.
5. Add more seeds and repeat.
6. Periodically warm the mortar by the fire (not on direct flame) to reduce oil viscosity.

Performance

Metric	Value
Force multiplier	1x (body weight only)
Oil recovery rate	20-35% of available oil
Throughput	0.5-1 kg seeds per hour
Build time	0 (found materials)
Best for	Small quantities, immediate need

This method wastes a lot of oil locked in the press cake. Use it only until you can build a lever press.

Method 2: Lever Press

The lever press is the first true force multiplier. A long beam pivoting on a fulcrum converts modest weight at one end into enormous pressure on the seed paste at the other.

How It Works

The principle is simple mechanics: a lever 2 meters long with the fulcrum 30 cm from the pressing end gives roughly a 6:1 force multiplication. Hang 20 kg of rocks from the far end and you get 120 kg of pressing force on the seeds. Lengthen the beam or add more weight and the force increases proportionally.

Construction

Materials needed:

• 1 strong beam, 2-3 meters long, 10-15 cm diameter (hardwood: oak, maple, ash)
• 2 upright posts, 60-80 cm tall, firmly set in the ground or anchored to a heavy base
• 1 cross-pin or rope to act as fulcrum pivot
• 1 pressing platform (flat stone or thick hardwood board)
• 1 collection trough or groove carved into the pressing platform
• Heavy rocks or a basket for weights
• Cloth bags for wrapping seed paste

Step 1: Set the uprights. Plant two sturdy posts 30-40 cm apart, firmly anchored. These posts hold the fulcrum pin that the beam pivots on. The posts should be solid enough to withstand the full leverage force without shifting.

Step 2: Install the fulcrum. Drill or carve a hole through each upright at the same height (about 40-50 cm from the ground). Insert a hardwood pin or iron rod through both holes. The beam rests on this pin.

Step 3: Prepare the pressing area. Directly below the short end of the beam (between the uprights), place your pressing platform — a flat stone with a shallow groove or channel carved around its edge to direct oil into a collection vessel.

Step 4: Prepare the beam. The beam passes between the uprights, resting on the fulcrum pin. The short end (30-50 cm from fulcrum to pressing end) pushes down on the seed paste. The long end (1.5-2.5 meters) extends outward for hanging weights.

Operation

1. Wrap warm, crushed seed paste in tightly woven cloth, forming a flat packet 3-5 cm thick. Thinner packets drain faster.
2. Stack 2-4 packets on the pressing platform, separated by thin wooden boards (like a multi-layer sandwich).
3. Lower the short end of the beam onto the top of the stack.
4. Gradually add weight to the far end of the beam. Start with 10-15 kg and increase over 30-60 minutes. Adding weight too fast squeezes paste out through the cloth rather than expressing oil.
5. Oil drips from the packets, runs along the platform grooves, and collects in a vessel below.
6. After 2-4 hours (or when dripping stops), remove the packets. The press cake can be re-ground, re-heated with a splash of water, and pressed a second time for an additional 10-15% yield.

Structural Failure

The fulcrum pin bears enormous force. A weak pin will snap, dropping the weighted beam suddenly. Use only dense hardwood (oak, ironwood) or metal for the pin. Inspect for cracks before each pressing session. Never stand under the weighted beam.

Performance

Metric	Value
Force multiplier	5-10x
Oil recovery rate	45-60% of available oil
Throughput	3-5 kg seeds per session
Build time	4-8 hours
Best for	Regular household oil production

Method 3: Screw Press

The screw press is the pinnacle of pre-industrial oil extraction. It converts rotational force into linear crushing force with enormous mechanical advantage and fine control.

How It Works

A large wooden screw threads through a fixed crossbeam. Turning the screw drives a pressing plate downward onto seed packets resting on a platform below. The screw’s thread pitch determines the force multiplication — a typical hand-cut screw with 1 cm pitch and a 40 cm turning handle delivers roughly 25:1 mechanical advantage before accounting for friction.

Construction

This is the most complex build and requires some woodworking capability.

Materials needed:

• 1 hardwood log, 15-20 cm diameter, 60-80 cm long (for the screw)
• 1 thick hardwood plank or beam for the fixed crossbeam (top frame)
• 2 heavy upright posts forming the frame
• 1 pressing plate (hardwood disc or flat stone, 20-30 cm diameter)
• A solid base platform with drainage channels
• Cutting tools capable of carving threads

Cutting the screw thread:

This is the hardest part. You need a spiral groove carved into a straight, round hardwood cylinder.

1. Mark a straight line down the length of the log. This is your reference line.
2. Wrap a strip of cloth or cord spirally around the log at the desired pitch (1-1.5 cm between wraps). Mark along the cord with charcoal to create the spiral guideline.
3. Using a chisel and mallet, carve a V-shaped groove following the spiral line, 8-10 mm deep.
4. Round the remaining ridges (the threads) to a smooth, rounded profile.
5. Test frequently by turning a matching nut (see below).

Cutting the nut (female thread):

The nut is a thick block of hardwood with a hole through the center, threaded to match the screw.

1. Bore a hole slightly smaller than the screw diameter through a hardwood block 8-10 cm thick.
2. Heat the end of the screw slightly and force it through the hole, compressing the wood to imprint the thread pattern.
3. Alternatively, carve the internal thread by hand using a hooked knife, matching the screw’s pitch.

Assembling the frame:

1. Set two heavy uprights firmly in the ground or bolt them to a solid base.
2. Fix the crossbeam horizontally between the tops of the uprights. The nut is installed in a hole through this crossbeam.
3. Thread the screw through the nut. The pressing plate attaches to the bottom of the screw.
4. The pressing platform sits at the base, directly below, with drainage channels leading to a collection vessel.

Operation

1. Stack cloth-wrapped seed paste packets on the base platform with separator boards between them.
2. Turn the screw handle clockwise to lower the pressing plate onto the stack.
3. Continue turning slowly. Oil begins to flow almost immediately.
4. Apply pressure gradually over 30-60 minutes. The screw allows precise, incremental pressure increases.
5. When the screw becomes very difficult to turn and oil has stopped flowing, the pressing is complete.
6. Reverse the screw to release. Remove and re-process press cakes for a second pressing if desired.

Performance

Metric	Value
Force multiplier	20-50x
Oil recovery rate	55-70% of available oil
Throughput	5-10 kg seeds per session
Build time	2-4 days (skilled woodworker)
Best for	Community-scale oil production

Press Comparison

Feature	Mortar	Lever Press	Screw Press
Tools to build	None	Basic	Woodworking tools
Force (relative)	1x	5-10x	20-50x
Oil recovery	20-35%	45-60%	55-70%
Speed	Slow	Moderate	Fast
Precision control	None	Low	High
Portability	Yes	No	No
Durability	Indefinite	Years	Years

Tips for Better Yield

• Always warm the paste before pressing. Warm oil flows more easily than cold oil. Heat the paste gently (not above 60C) with a splash of water before wrapping in cloth.
• Press thin layers. Multiple thin packets (3-5 cm) extract better than one thick mass because oil has less distance to travel to escape.
• Increase pressure slowly. Rapid force squeezes paste through the cloth rather than oil out of the paste.
• Re-press the cake. Break up the press cake, add a small amount of warm water, re-grind, and press again. Second pressing yields 10-20% additional oil.
• Keep cloth tight. Loose wrapping lets paste ooze out and clogs drainage channels. Wrap firmly and tie with cord.

Key Takeaways

• A mortar works for emergency oil extraction but wastes 65-80% of available oil.
• The lever press is the best balance of simplicity and performance — build one as soon as you have basic woodworking capability.
• The screw press is a community investment that pays for itself in a single season of production.
• Warm paste, thin layers, and gradual pressure are more important than raw force.
• The press cake still has value: animal feed, fire fuel, or fertilizer.