Cotton Processing

We’ve Spent A Century Perfecting Our Process

Our finished products go through an extensive purification process before they ever end up in the hands of consumers.

Cotton-Bleaching-Stages

Raw cotton arrives initially in densely packed bales, and these bales are subjected to a series of steps over time, ultimately undergoing a dramatic change. While raw cotton contains fiber, it also carries small plant parts and field trash (non-lint or foreign matter) that must be dealt with.

Many people are also unaware that cotton fiber has a coating of natural waxes that protect it from rain, which ultimately makes it hydrophobic (which is a fancy word for water repellent). This means raw cotton is unsuitable for use in many consumer products that require absorbency, a trait that is critical in many cotton applications.

Keep in mind this is just one example; but it illustrates, perfectly, why our cotton process and fiber finishes must be customized to meet a demanding range of customer needs.

Step One: Mechanical Purification and
Cake Formation

The first step in our process is to open the dense tufts of fiber from the bales. The fiber is fed into a hopper that mechanically picks the fiber tufts apart, and then the opened fiber is fed to mechanical cleaners that open the fiber even more. The end goal is to allow the non-lint material to be more easily extracted from the fiber.

While the aim is to remove all of the non-lint material, in reality it’s never 100% removed. The remainder of the process is conducted in large vessels called kiers. These kiers can be heated and pressurized to speed up the wet purification process.

Cotton is wet out and packed into large cakes with a hole in the middle (for a perfect visual, imagine a Bundt cake). The cotton cakes are then lowered down into the kier and it is closed.

Step Two: Scouring

Now, a solution containing sodium hydroxide is pumped into the kier. As the kier is heated and pressurized, the alkali solution is continuously pumped through the cakes. During this time the waxes on the fiber are saponified (converted into water soluble soaps), the remaining plant matter is softened, and the pectins and other non-cellulosic materials are suspended so they can be washed away.

After a predetermined length of time at elevated temperature and pressure to allow for a complete scouring, the saponified waxes and suspended materials are rinsed away with fresh water. After scouring, the cotton fiber is absorbent and any small amounts of plant matter that remained are softened.

Step Three: Purifying

Once the scouring rinse is drained, a purifying solution is pumped into the kier. Barnhardt uses only hydrogen peroxide as the oxidizing (purifying) agent, which makes our process Totally Chlorine-Free (TCF).

The hydrogen peroxide whitens the fibers by oxidizing the coloring matter. Since the scouring process softened the remaining plant matter, the purifying agent can penetrate the plant matter more effectively, and make it white as well.

The purifying solution is pumped through the cakes for a predetermined time at an elevated temperature to allow for elimination of all color bodies. Next the purifying solution is rinsed away with fresh water and the tank is drained.

At this point, all of the fiber’s impurities and coloring bodies have been removed, and the cotton fibers are pure cellulose.

Step Four: Fiber Finishing

Though the natural fiber finish (wax) has been removed, the fiber can be difficult to process due to a high level of fiber-on-fiber friction. Therefore, to allow for efficient processing on high-production web-forming equipment, a fiber finish (lubricant) must be added.

Many types of fiber finishes can be applied depending on the application need. These finish solutions are pumped through the cakes, which allows the desired level of finish to be applied to the cotton fibers. Once that desired level is reached, the finish solution is drained.

Step Five: Opening and Drying

Now the wet cakes are re-opened into tufts of fiber, and the fiber is dried to specific moisture levels that have been predetermined by customer specifications.

Once baled, the moisture content is measured and then printed on labels that are attached to each and every bale, a final signature that lets our customers know that their cotton has gone through Barnhardt’s meticulous process to ensure cotton perfection.