The Truth About Fiberglass Casts for Bone Fractures

woman with fiberglass cast for wrist fracture
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When you break a bone, your doctor will likely recommend that you have a cast put on to help stabilize the injury so that it can heal properly. You may have heard that fiberglass casts are a good option, but is that really true? 

This blog post will give you all the information you need about fiberglass casts, from how they are applied to how long you’ll have to wear them. We’ll also explore the pros and cons of fiberglass casts and provide tips on taking care of your cast while your fracture heals. If you’re considering a fiberglass cast, this guide is a must-read before making your decision.

What is a Fiberglass Cast?

A fiberglass cast is a type of medical dressing made of synthetic materials used to support and protect bones that have been broken or joints that need stabilization. 

A typical fiberglass cast is made of three layers. The inner layer is a stockinette, which is a knitted fabric. The middle layer is a cotton bandage that is wrapped around the limb. The outer-mostlayer is a resin and fiberglass composite that is activated and then wrapped around the other layers. The purpose of the three layers is to provide support and protection for broken bones and skin. 

The fiberglass outer layer is hard and strong, and it helps to keep the inner layers in place. The cotton bandage helps to absorb any sweat or moisture that may build up under the cast, and the stockinette helps to prevent the skin from rubbing against the rough edges of the fiberglass. The two inner layers can also protect you from any cast saw accidents.

Fascinating History of Fiberglass Casts

The medical practice of immobilizing broken bones with casts and splints has been around for centuries, with the earliest known examples dating back to ancient Egypt. The first plaster casts were made from a mixture of plaster of paris and water. This was the standard treatment of broken bones for many years. In the 1970s, a team of doctors sought a material that would be lighter and more comfortable than a plaster cast. After trying a variety of other synthetic materials, fiberglass casting tape was developed, and it quickly became popular with patients seeking treatment for their injured arm or leg. 

How are Fiberglass Casts Applied?

A nurse applying a stockinette to patient with broken wrist
mushegovdima - stock.adobe

The application process of a fiberglass cast is relatively straightforward, but it must be done quickly to avoid the material hardening before it is in the desired shape. 

First, a medical professional may clean your skin with soap and water to prepare for the cast application. Next, they will apply a stockinette to your injured limb. After that, they will apply a soft cotton padding for cushioning. Finally, they will apply several layers of resinous fiberglass casting material. 

The material will harden quickly, so the clinician will need to work quickly to mold the cast to the desired shape. Once the cast is in place, you should not remove it yourself. You'll need to see a doctor or cast technician to have it removed. The entire process can take about 30 minutes depending on what is being casted.

Fiberglass Cast Drying Time

Once a fiberglass cast has been applied, it can take some time for the cast material to dry. The number of fiberglass layers and the air's humidity can affect the drying time, but typically it takes 1-2 hours for the cast to fully harden. During this time, it's important to avoid moving or putting weight on the cast, as this could disrupt the drying process and cause the cast to misshapen. Once the cast is dry, it will provide support and protection for the injured area while it heals.

How Long Does a Fiberglass Cast Stay On? 

Patients can wear most fiberglass casts for up to six weeks, but this will vary depending on the nature of the injury. In some cases, a fiberglass cast may need to be removed sooner if it begins to cause irritation or discomfort to the affected limb. If you need to be immobilized for longer, you may need to have your cast replaced.

How is a Fiberglass Cast Removed?

Young girl getting her fiberglass cast cut off with a cast saw
phofotos - stock.adobe

Once the bone has mended, the fiberglass cast needs to be removed from the body by a medical professional. The most commonly used tool for cast removal is a cast saw. This type of saw uses a very thin, vibrating blade that can quickly cut through the materials making up the cast. However, because the blade is so thin, sharp, and fast moving, it is also important to be very careful when using a cast saw. Additionally, technicians may use cast spreaders or ultra-strong scissors. These tools can also be effective in cutting through the materials making up the cast. Usually, the entire process takes between 15 and 20 minutes and can depend on the size of your cast. 

Fiberglass Cast Care

When you have a cast put on, it is important to follow the doctor's instructions for care. Here are some cast care tips:

  • Try to keep the cast clean and dry. The fiberglass part of the cast is designed to repel water, but if the padding underneath gets wet, it can lead to skin irritation or even infection. If you get your cast wet, use a hair dryer on the cool setting to dry any wet areas.
  • Never shove objects inside the cast. It may be tempting to reach in with something to scratch an itch, but doing so can damage the skin, may lead to infection, and can disrupt the healing process.
  • Do not put any lotions, oils, or powders on the skin under the cast without first consulting your doctor. This can cause skin irritation.
  • Avoid activities that could impact or put pressure on the area with the cast. This could potentially damage the cast or cause further injury.

If you have an itchy cast or you notice your cast has a foul odor, learn more about how to deal with these common problems. 

Can you Get a Fiberglass Cast Wet? 

Man taking a shower with a fiberglass cast
Филипп Очеретный - stock.adobe

When you have a fiberglass cast, it's important to avoid getting it wet. If the cast gets completely submerged in water, it can cause the fiberglass to unravel and the cotton bandage to swell. This damages the materials and weakens the cast. 

Although, many fiberglass casts can be made waterproof by using waterproof padding material under the hard cast shell. Rather than using traditional cotton padding, waterproof casts use a special padding material that is impervious to water.

If your fiberglass cast is not waterproof, be sure to cover your cast with a waterproof sleeve or bag when taking a shower or bath. Patients can use special covers to protect the cast from getting wet. Learn more about how to keep your cast dry in the shower

If you have a wet cast, you should dry it off as soon as possible. You can use a hair dryer on a cool setting to help dry the inside of the cast. If the cast is wet on the inside, you should call your doctor for medical advice. 

Fiberglass Cast Advantages and Disadvantages

A patient with an itchy foot plaster cast using knitting needle to scratch
JRJfin - stock.adobe

When it comes to broken bones, the type of cast you receive can make a big difference in your recovery experience. Let’s take a look at the advantages and disadvantages fiberglass casts offer. 


Fiberglass is lighter and more porous than plaster, allowing airflow and reducing the risk of itchy skin This makes it more comfortable for patients to wear for extended periods of time. Fiberglass arm casts can also be stronger than plaster casts, making them less likely to break if they are bumped or experience any other type of impact. However, fiberglass can be more expensive than plaster, and it can also cause skin irritation in some people. Overall, though, fiberglass is a versatile and durable material that can be an excellent choice for a cast.


Despite its advantages, fiberglass isn't without its drawbacks. One of the most common disadvantages of fiberglass casting is that it sets very quickly. This can be a problem for less experienced medical providers who may not have enough time to properly wrap the injured extremity before the cast sets. In addition, fiberglass casts have a bad reputation for being smelly and uncomfortable.

Another disadvantage to consider is that a special cast saw is required to remove the cast once the injury has healed. While this may not be a big inconvenience for some, for others it can be quite scary. Additionally, using a cast saw can be dangerous. If not used properly, the saw can cause further injury to the patient by burning or cutting the skin. For this reason, it is important to make sure that the medical provider removing the cast is properly trained and knows how to use the cast saw correctly. 

When to See a Doctor

Even with the best care, there are times when you may need to see a doctor for your cast. If the skin underneath the cast becomes unbearably itchy, or if you notice a bad smell coming from the cast, these could be signs of an infection. In either case, seeking medical attention is essential in order to ensure that your injury heals properly.

Is there an Alternative to a Fiberglass Cast? 

Traditional fiberglass casts can be cumbersome and uncomfortable, making it difficult to go about your normal daily activities. Fortunately, there is a new product on the market that offers all the healing benefits of a traditional cast, without any discomfort. 

Cast21 is a new type of medical casting alternative that has been developed for the 21st-century lifestyle, boasting many advantages over traditional casting methods. Unlike traditional casting, Cast21 doesn't require any messy plaster or fiberglass bandages. Instead, the injured limb is simply placed into an open lattice sleeve which is then filled with a fast-curing proprietary formula. The result is a strong, yet seemingly weightless cast alternative that is comfortable to wear. 

Because the Cast21 system is completely waterproof, it can be worn while bathing or swimming. Overall, Cast21 provides a more convenient alternative to traditional casting methods. Plus, they're available in a variety of colors to suit your style. 

If you or someone you know has suffered a broken bone, be sure to ask your doctor about Cast21 or contact our team of professionals with any questions you may have. 

Medical Disclaimer

Cast21's articles and content are for informational and educational purposes only. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

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