# Hydraulic press

> Multiplying force with water

- Date: 1795
- Era: Industrial age
- Domain: [Tools & Making](https://lastcodex.org/en/domains/tools/)
- Rebuild stage: IV (Science & industry)
- Difficulty: 3/5
- URL: https://lastcodex.org/en/inventions/hydraulic-press/

A hydraulic press multiplies force with water. A small hand pump forces water into a closed cylinder, and the wide piston in it, the ram, pushes with a force as many times greater as its area is larger than the pump piston's, while moving that much less. Blaise Pascal described the principle in a treatise written around 1651 to 1654 and published in 1663. Joseph Bramah patented a working press in London in 1795; a leather collar that tightens under pressure made it seal, and its presses packed cloth, hay and oil seeds before growing into the forging presses of the 20th century.

![Hydraulic press · Multiplying force with water](https://lastcodex.org/_astro/plate.Tahv0i4c_EwNwg.webp)

## Legend

1. Pump lever
2. Pump plunger and its small cylinder
3. Non-return valves
4. Pipe to the large cylinder
5. Ram and its cylinder
6. Platen pressing against the fixed head

## What it is

A hydraulic press squeezes, flattens or shapes things with a ram pushed by water. It has two cylinders of very different sizes joined by a pipe and filled with water or oil. A worker drives a narrow plunger into the small cylinder with a lever, and the liquid pushes up the wide ram in the large one with far greater force. The ram carries a platen, and the load between the platen and a fixed head is pressed as hard as the frame can bear.

In a press of the kind Joseph Bramah built in London in the early 19th century, the large cylinder sits in a cast-iron base, and iron columns tie the base to a fixed head at the top, so that the frame takes the reaction of the ram. A hand pump on one side draws water from a cistern and forces it along a narrow pipe under the ram. A small cock lets the water back out to lower the ram when the work is done.

## How it works

Water barely compresses, so pushing on it in a closed vessel raises its pressure, and that pressure acts equally on every wall and piston it touches. The force on a piston is the pressure times the piston's area. With the same pressure under both, a ram a hundred times larger in area than the pump plunger pushes a hundred times harder.

![Two upright glass cylinders of water on a wooden base, joined at the bottom by a tube, with an arrow pushing down the narrow piston on the left and an arrow lifting the wide piston on the right](https://lastcodex.org/_astro/v1.CWUerzBf_YU2uW.webp)
_The narrow piston goes down a long way; the wide one rises a little, with greater force._

The gain is paid for in distance. The water the plunger drives out of the small cylinder spreads under the whole width of the ram, so the ram rises only a hundredth of the plunger's stroke in that example. Work, force times distance, comes out the same at both ends, less what friction takes. Suppose the plunger has an area of 1 cm² and the ram 100 cm². A push of about 100 newtons, the weight of 10 kilograms, then gives about 10,000 newtons on the ram, the weight of a tonne, and the pump lever multiplies the worker's push again before it reaches the plunger.

The pump works in strokes, and two non-return valves keep the water going one way. On the up stroke, the plunger draws water from the cistern through the inlet valve; on the down stroke, that valve closes and the water is forced out through the outlet valve into the pipe. The outlet valve closes when the plunger rises again, so the ram stays up between strokes. Opening the release cock lets the water flow back and the ram sink.

The ram has to slide out of its cylinder without the water escaping round it. In the early presses this seal is a ring of leather bent into a U and set in a groove at the mouth of the cylinder, with the open side facing the water. The water pushes the two lips of the U apart, against the ram and the cylinder wall, so the higher the pressure, the tighter the seal.

## How to do it

This demonstration shows the gain in force with two syringes. You need two needle-free syringes of different sizes, for example 5 ml and 50 or 60 ml, about 30 cm of flexible tube that fits tightly on both nozzles, a glass of water with a drop of food colouring, a paperback book, a towel and safety glasses.

Draw the small syringe full of coloured water, fit one end of the tube on it and push gently until water comes out of the other end. Push the large syringe's plunger all the way in, fit it to the free end of the tube, and check that there is little air in the tube. Lay the syringes on the towel.

![Two needle-free syringes, one small and one large, joined by a clear tube full of coloured water, lying on a wooden board](https://lastcodex.org/_astro/v2.DDXcwpOm_2sO6ps.webp)
_Two syringes joined by a tube of water: a small pump and a large ram._

Push the small plunger in by its whole stroke and watch the large one: it moves out a much shorter distance, and its scale shows the same volume of water arriving as left the small one. Now hold the large syringe upright, plunger on top, and lay the book on its plunger. A light push on the small plunger lifts the book. Swap the roles: put the book on the small syringe and push the large plunger, and you will find you must push much harder to move the same weight. Finally, press the two plungers against your thumbs at the same time: the large plunger pushes back much harder for the same pressure.

## History and evolution

Blaise Pascal described the principle in his treatise on the equilibrium of liquids, written around 1651 to 1654 and published in Paris in 1663, after his death. He imagined a vessel full of water closed by two pistons, one opening a hundred times larger than the other. One man pushing the small piston, he wrote, holds back a hundred men pushing the large one, so that the vessel becomes "a new machine to multiply forces". He also noted the price: when the small piston is pushed in by an inch, the large one moves out only a hundredth of an inch.

A working press came more than a century later. Joseph Bramah, a London engineer already known for his [lock](/en/inventions/lock-and-key/), patented one in 1795, No. 2045, under the title "obtaining and applying motive power". His press pumped water under the ram of a large cylinder with a [piston pump](/en/inventions/piston-pump/). The difficulty was the seal: a packing of hemp or leather tight enough to hold the water gripped the ram so hard that the press could barely move. The answer was the leather collar bent into a U, which only tightens as the pressure rises. James Nasmyth, writing in 1863, credited it to Henry Maudslay, who worked for Bramah until 1797, and the European Route of Industrial Heritage does the same; according to the history edited by John Cantrell and Gillian Cookson, the _Mechanics' Magazine_ named Benjamin Hick of Bolton a year later.

![A Bramah press squeezing a bale of folded woollen cloth between the platen and the head, a worker at the pump lever](https://lastcodex.org/_astro/v3.B79f7s1N_dGGO.webp)
_A Bramah press packing woollen cloth, one of its first uses._

The first presses went to the woollen trade, to pack hay and to press seeds for [oil](/en/inventions/oil-press/). Bramah supplied presses to the Leeds cloth maker Benjamin Gott, whose workers resisted their installation, and he later went to court to get ten of them back. The Sheffield Museums date the first use of a Bramah press at the Tower of London to 1806. Bramah went on to apply water pressure to [cranes](/en/inventions/crane/) and to the gates of [canal locks](/en/inventions/canal-lock/).

Powered pumps later replaced the hand lever, and hydraulic cylinders came to drive guillotine shears and the cocoa presses used for [chocolate](/en/inventions/chocolate-making/). Under a US Air Force programme to build very large presses, the Loewy company built a 50,000-short-ton forging press for Wyman-Gordon at Grafton, Massachusetts, in service in October 1955. It forged aircraft parts, among them parts of the Boeing 747.

## Key facts

- Pascal's treatise on the equilibrium of liquids: Written about 1651–1654, published in 1663
- Bramah's patent for the hydraulic press: London, 1795, No. 2045
- Gain in force: Area of the ram divided by area of the pump plunger
- Wyman-Gordon forging press, Grafton, Massachusetts: 50,000 short tons, in service in October 1955

## Requires

- [Piston Pump](https://lastcodex.org/en/inventions/piston-pump/): Water raised by valve and piston (c. 270 BCE)
- [Iron Smelting](https://lastcodex.org/en/inventions/iron-smelting/): Wider adoption around 1200 BCE; ore, charcoal and a bloomery (c. 1,200 BCE)
- [Leather Tanning](https://lastcodex.org/en/inventions/leather-tanning/): Raw hide, oak bark and months in pits (c. 1,500 BCE)

## Leads to

- [Hydraulic manipulator arm](https://lastcodex.org/en/inventions/hydraulic-manipulator/): Joints moved by oil under pressure (1947)
- [Self-climbing tower crane](https://lastcodex.org/en/inventions/self-climbing-tower-crane/): A crane that adds sections to its own mast (c. 1955)
- [Synthetic plastics](https://lastcodex.org/en/inventions/synthetic-plastics/): Materials built from long molecules made in chemical plants (1907)

## Sources

- [Blaise Pascal, Traitez de l'équilibre des liqueurs et de la pesanteur de la masse de l'air (Paris, 1663)](https://archive.org/details/bub_gb_F8UPAAAAQAAJ), Internet Archive
- [Blaise Pascal](https://imss.fi.it/vuoto/epasca.html), Museo Galileo, Institute and Museum of the History of Science
- [Pascal Blaise : Pascal savant](https://www.universalis.fr/encyclopedie/blaise-pascal/2-pascal-savant/), Encyclopædia Universalis
- [Henry Maudslay and the Pioneers of the Machine Age (ed. J. Cantrell and G. Cookson, 2002)](https://gwern.net/doc/technology/2002-cantrell-henrymaudslayandthepioneersofthemachineage.pdf), Tempus Publishing
- [Joseph Bramah](https://www.gracesguide.co.uk/Joseph_Bramah), Grace's Guide to British Industrial History
- [Bramah press](https://sheffieldmuseums.org.uk/whats-on/bramah-press), Sheffield Museums
- [Wyman-Gordon 50,000-Ton Hydraulic Forging Press, National Historic Mechanical Engineering Landmark (1983)](https://www.asme.org/wwwasmeorg/media/ResourceFiles/AboutASME/Who%20We%20Are/Engineering%20History/Landmarks/89-wyman-gordon-50000-ton-hydraulic-forging-press.pdf), American Society of Mechanical Engineers
- [The forging industry, always advancing (L. Kren, 2013)](https://newequipment.com/metal-forming/article/21922860/the-forging-industry-always-advancing), New Equipment Digest
- [Henry Maudslay (1771–1831)](https://www.erih.net/how-it-started/stories-about-people-biographies/biography/maudslay), European Route of Industrial Heritage

Fact-checked on 2026-10-19.

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