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A Cotton Gin

A Cotton Gin

Introduction: (Initial Observation)

The cotton gin is a device for removing the seeds from cotton fiber. Before invention of the cotton gin, cotton seed had to be removed by hand, work that was usually performed by slaves.

The Cotton Gin is said to have begun the Industrial Revolution, and made an immediate impact upon American industry.

In this project, you will study the cotton gin and learn how it works? You will also study the history of the cotton gin and its affect in agriculture, industry, and economy of the United States. Finally, you will construct a model of a cotton gin.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Adult supervision and support is required.

Information Gathering:

Gather information about the cotton gin and its inventor. Find out how this invention affected the economy of the United States. Review the designs and descriptions about different cotton gins in order to understand the mechanism of its functionality.

You may find books related to cotton and the cotton gin in your local library. You may also find a large amount of information about cotton gin online.

Keep track of where you got your information from.

The following are samples of information that you may find:

Inventor of cotton gin, Eli Whitney

Born in Westborough, Massachusetts, in 1765, Eli Whitney found an early interest in machinery. Working in his father’s woodworking shop, Whitney could be found taking apart such items as pocket watches and clocks, studying the intricate mechanisms and then putting their parts together again.

At the relatively early age of fourteen, he had opened his own nail-making business and then a pin-making shop, earning a fairly good wage for his efforts.

After graduating from Yale University in 1792, Whitney, in need of money to pay off some outstanding debts, accepted a private tutoring position on a plantation in Georgia owned by a Mrs. Catharine Greene. Because of his interest in mechanics, he took to heart the seriousness of doubts and growing difficulties in cotton production that were presented to him by the local planters. With his experience and success in mechanical problems, Whitney took it upon himself to find a feasible answer to the growers’ woes.

Birth of the Cotton Gin

Not long after listening to the growers speak of their troubles, Whitney began to experiment and arrived at his basic design of the cotton gin. This machine was created to ease the tremendous burdens of those who labored to pick the seeds from the cotton. Many labored under difficult conditions, and even under good conditions, one could manage to clean only one pound of the crop a day.

With his invention, Whitney made it possible to clean fifty pounds per day.

Basic Design

Whitney had arrived at a basic design: a cylinder with wire teeth would pull the cotton fiber. The raw cotton from the field could be fed on one side of the cylinder and as it spun around, the teeth would pass through small slits in a piece of wood, pulling the fibers of the cotton all the way through but leaving the unwanted seeds behind.

This crudely made box, with a cylinder, a crank, and a row of saw-like teeth had made it possible to clean fifty times more cotton than could be cleaned by hand.

It is said to have begun the Industrial Revolution, and made an immediate impact upon American industry.

The first cotton gin built by Whitney in 1793 was simply a wooden box that spun cotton around a drum and pulled it through a set of wire teeth mounted on a revolving cylinder, the fiber passing through narrow slots in an iron breastwork too small to permit passage of the seeds

How does it work? Design concept:

The cotton seeds are relatively large. You can almost compare them with the seeds that you see in some oranges.

Original cotton engine consisted of spiked teeth mounted on a boxed revolving cylinder which, when turned by a crank, pulled the cotton fiber through small slotted openings so as to separate the seeds from the lint. Simultaneously a rotating brush, operated via a belt and pulleys, removed the fibrous lint from the projecting spikes.

Economical effects:

In 1793, approximately one hundred and eighty thousand pounds of cotton was harvested in the United States. Two years later, that harvest grew to more than six million pounds; by 1810, an astounding ninety three million pounds were brought to harvest.

Chemistry of cotton:

Cellulose, the main structural component of cell walls, is a polysaccharide made up of anywhere from 100 to 15,000 glucose molecules attached to one another. In the case of cotton, this creates a strong material that is absorbent, versatile, dyes well, and withstands many washes. As additional benefits, each cotton plant produces a large amount of fiber, and cotton costs less to process than other plant fibers.

Cotton plant:

Cotton bolls, as the fruit capsules are known commercially, mature 50-80 days after fertilization. At maturity, they split open to reveal masses of long, white seed hairs (lint), each of which is attached to a black seed. This modification enables the seed to be dispersed by the wind.

Ginning of cotton:

The gin removes the seeds so that the lint can be packed into tight bales. The quality and price of cotton are determined based on several factors: length of individual fibers, or staple; grade (color, brightness, and amount of foreign material contaminating the final product); and character (diameter, strength, uniformity, and smoothness of individual fibers).

The ginning of cotton produces tons of seeds, which were once deemed a waste-disposal problem but are now a valuable by-product. The separated seeds go to oil mills, where they are further delinted of the shorter, fine hairs that adhere to the seed coat after initial ginning. This shorter lint, sometimes called linters, is used to make paper, furniture padding, and the tips of cotton swabs. The seed is then cracked, the kernel removed, and the oil extracted.

A seed from the cotton plant. The seed is approximately 3/8 inch long and 3/16 inch wide. It is covered by a soft fibrous substance. Sometimes the seed will appear blackish and fiberless (no cotton adhering to the seed).


Models of cotton gin made by other students.

Do these models show the concept and mechanism of cotton gin? Can you make a better model from paper, wood, plastic or metals?

All these models are missing one important component, the slot.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this experiment is to construct a model of a cotton gin and display how cotton fibers can be pulled through a slit while the seeds cannot.

Also see the experiment #2

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Note that this is a display and engineering project. You will not define variables like experimental projects. So you can skip this part.

Your variables are design variables such as choices of material and size for each part.

Also see the experiment #2


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Not needed for a display/ engineering project.

Also see the experiment #2

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1: Make a model of a cotton gin

Introduction: According to legend, Eli Whitney conceived of the idea of the gin in two ways: by watching a cat reach through a fence, try for a chicken, and come away with nothing but feathers and by hearing Catherine Green say as she handed him a hearth brush, “Mr. Whitney, here’s what you need,” to remove the seeds from the cotton. You can use the same ideas to construct a cotton gin that may or may not be similar to Mr. Whitney’s design.


  1. Construct a small wooden or cardboard box.
  2. Mount a wooden or cardboard spiked wheel in the center of the box such that you can turn it using a crank.
  3. Mount a slotted sheet of cardboard or wood in the box such that some teeth of the wheel come through the slot enough to grab cotton fibers.

4.Enter some cotton bolls and spin the wheel to show how fibers pass through the slot.

5.In your model you may skip the brush that Mr. Whitney used to remove the cotton from the teeth or spikes of the wheel. This action can now be performed by air.

If you want to use a brush, note that the brush must spin faster than spiked wheel in order to work.

Following are some sample images of this model:

The round saw is a main component in each cotton gin. Real cotton gins have many saws mounted side by side with some distance.

You cut a round saw from cardboard, soft metals, and hard plastics.

Make a hole in the center of the saw so the pencil, wood dowel or any other axle that you choose can go through.

You don not have to actually cut the hole. Cut two and sign over each other with about 45º difference. In this way the hole will open with the force of the wooden dowel or pencil. This also makes it easy for the saw to be glued to the axle.

The wheel is then mounted in a box while part of the saw is going through a slot on the plane that separates the box in two parts.

The box can be made from cardboard, balsa wood or other types of wood.

Drop some cotton and some seeds in the machine to show that saw pulls the cotton through the slot but seeds can not go through. If you don not have real cotton seeds, use beans or orange seeds to simulate cotton seeds.

Experiment 2:

Construction of a cotton gin model is an engineering or demonstration project that does not require any question, hypothesis, data and graph. Some students may want to do a cotton related science project that requires such parts. This is how you may do that.

Start with a question like this: What is the ratio of lint, seed and linter in cotton bolls?

Propose a hypothesis like this: Long fibers or lint form more than 50% of the cotton bolls. Seeds are probably about 40% and linters or small fibers are the smallest portion of about 5%.

This is how you define variables:

  • The independent variable is the parts of a cotton boll. (Lint, Linter, Seed)
  • The dependent variable is the ratio of each portion.
  • Constants are the type and source of the cotton bolls.


  1. Get about 100 grams of cotton bolls and then measure and record their total mass (weight).
  2. Using your hands and simple household tools separate the lint, the linter and the seeds.
  3. Measure and record the mass (weight) of each portion and divide that by the total mass in order to get the ratio for each portion.
  4. Record your data in a table like this:
Materials total Weight of bolls Weight of each component Ratio
Lint 100g
Linter 100g
Seeds 100g

Make a graph:

Use the above results table to make a bar graph. Make one vertical bar for each of the components. Write the name of the component (Lint, Linter or seed) below the bars. The height of each bar will be the ratio of the component that ball represents. For example you may use a 62 millimeter bar for the component that is 62% by weight.

To calculate the the ratio, you must divide the weight of each component by the total weight of bolls.

Finally remove the extra information from your data table to make your results table like this:

Materials Ratio

Make a graph:

Use the above results table to make a bar graph. Make one vertical bar for each of the components. Write the name of the component (Lint, Linter or seed) below the bars. The height of each bar will be the ratio of the component that ball represents. For example you may use a 62 millimeter bar for the component that is 62% by weight.

Materials and Equipment:

You have many options for material.

The spiked wheel can be a round saw. Alternatively you can make it by inserting nails in a wooden wheel and then cut the ends of the nails. The simplest way is to cut the spiked wheel from cardboard.

The axle of the wheel can be a wooden dowel, a pencil, or a metal rod.

The box itself can be made of wood or cardboards.

If you don not have access to cotton balls, buy some cotton and mix it with orange seed to simulate cotton seeds.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


If you do any calculations for this project, write your calculations in this section of your report.

Summery of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Since this is an experimental/ engineering project, write down what problems did you face while constructing your cotton gin and how did you overcome each project.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Write if your cotton gin works. How can you improve it if you choose to make more of these.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

This item was for sale on EBAY in April 2005.

Lot includes original bill of sale, newspaper article documenting the sale and photo of cotton gin with log house where it was used. Also included is an old photo of Cotton gin with Georgia dignataries, including the Governor, a Senator, buyer and seller. A portrait of Eli Whitney, tools used by Whitney while working on the machine, and other interesting artifacts related to this cotton gin accompany the lot. This cotton gin is an extremely important piece of history and was one of the main attractions of The Atlanta Museum where it was on display. 50″ Long x 20″ w x 35″ h

Original Design of Cotton Gin by Eli Whitney