Initially developed by 3M around 1945-46 and called No. 33 tape, electrical tape, also known as thermal insulation or insulating tape, is a must-have for any licensed electrician or apprentice. Compared to other types of tape, electrical versions stretch to wrap tightly around wiring while also providing insulation.
Since the tape is built for use in specific tasks, where other tapes won’t do, electricians can use electrical tape in just about any job where wiring and cabling are needed, including at home or in commercial and industrial settings.
However, it would be best if you didn’t use electrical tape in situations where wiring is badly damaged, connecting junction boxes, switches, or outlets, or as a replacement for wire nuts.
What Is Electrical Tape Made of?
To achieve its trademark stretchability, elongation, and ability to wrap tightly around wires that conduct electricity, electrical tape is typically constructed from polyvinyl chloride (PVC).
Unlike other tape types, electrical versions also feature a rubber-based adhesive that’s non-corrosive, stands up better to vibration and temperature changes, and that provides resistance against drying out (unlike regular tapes), which could lead to a potential fire hazard.
To ensure it meets your needs, most electrical tape is tested and listed by Underwriting Laboratories (UL) or the CSA Group.
Can You Use Duct Tape as Electrical Tape?
The short answer is no; you shouldn’t use duct tape as a replacement for standard electrical tape. Why?
Electrical tape is specifically manufactured to wrap around wires and cables and insulate them, thereby preventing fires. The tape is also generally listed by Underwriter Laboratories (UL) for protection up to 600 volts per wrap.
On the other hand, duct tape is a general-purpose version that features a cloth back, which is coated with polyethylene, making it water-resistant and allowing it to stick to just about any surface. Compared to electrical tape, duct tape doesn’t work as an insulator, isn’t voltage rated, is flammable, and degrades quickly. Hence, it – or any type other than electrical tape – is unsafe to use for wrapping wires or cables.
Types of Electrical Tape
Electrical tape comes in many types, and the one you should use depends on the job you’re tackling. Below, you’ll find several of the most common.
Waterproof Electrical Tape
Regardless of color, traditional vinyl electrical tape is water-resistant but not waterproof. With this said, a popular alternative is self-bonding electrical tape (also known as self-amalgamating tape), which comes in a variety of lengths and widths, depending on your project.
Speaking of which, self-bonding electrical tape can come in especially handy when splicing and connecting wires and cables to high voltage applications. Like the traditional version, you can also use the tape for general-purpose, lower-voltage electrical projects.
- Quickly bonds to itself, but not to the wire or insulation you’re wrapping.
- Available in different lengths and widths, depending on the job you’re tackling.
- Usable for high and low-voltage applications, including projects around the house.
- It resists water and temperature fluctuations and won’t dry out.
- It can be more expensive than traditional electrical tape.
Mastic Electrical Tape
Mastic electrical tape features extra-thick rubber insulation that’s moisture-resistant and rated for indoor and outdoor use. After peeling off the backing and applying the tape to wire insulation, it conforms to the surface and fuses to itself, creating a moisture-resistant barrier.
Because it resists moisture and UV rays, you can use mastic tape inside or outside.
- Insulates low-voltage wires.
- Self-conforming to easily cover irregular surfaces.
- Self-fusing for weather and moisture resistance.
- Works well in a range of temperatures.
- Useful indoors and outdoors.
- Not ideal for most indoor electrical projects.
- Adheres to itself and the surface, which could present more work (and wasted expensive tape) if you make a mistake when applying.
Varnished Cambric Electrical Tape
Varnished cambric electrical tape uses straight-cut woven cotton cambric fabric as its foundation, hence the name. The fabric is coated with yellow insulating varnish, which delivers flexible, insulating, and moisture-resistant properties.
Common uses for cambric electrical tape include insulating an inline splice, installing a split bolt connection, and insulating a bus bar, to name just a few.
- Flexible insulating fabric.
- Performs well across a variety of temperatures, including up to 221 degrees Fahrenheit.
- It can be handy for splicing, installing a split bolt connection, or insulating a bus bar.
- You can pay more than $100 for a single roll of varnished cambric electrical tape, depending on the width.
Rubber Electrical Tape
Rubber electrical tape is a broad term that references a few different types:
- Primary Insulating Tape – Self-bonding tape made from ethylene propylene rubber that stretches around wires and cables to form a tight seal.
- Self-Fusing Silicone Rubber Tape – Thin silicone rubber tape that’s ideal for medium voltage applications. This version isn’t quite as stretchy as primary insulating tape.
- Cable Jacket Repair & Mining Tape – Made from vulcanized CSM rubber and provides site repairs in commercial and industrial environments.
- Several different types, depending on your needs.
- Repels moisture.
- Works for indoor and outdoor applications.
- Operating temps up to 221 degrees.
- More options mean that you’ll need to choose the proper rubber tape for the job.
Vinyl and PVC Electrical Tape
Standard electrical tape comes in two types: the most popular is vinyl, although it also comes in PVC versions. What’s the difference?
PVC Electrical Tape
You can use polyvinyl chloride, abbreviated as PVC, electrical tape outdoors, even when the temperature drops. It also helps resist metal corrosion and abrasion. As a result, PVC electrical tape is ideal for wrapping exposed electrical wires and even plumbing.
Vinyl Electrical Tape
Comparatively, vinyl electrical tape is best suited for indoor applications since it’s not as resistant to cold temperatures as PVC. Still, it’s a durable waterproof option that gets the job done.
- PVC electrical tape is ideal for outdoor applications.
- PVC is weather-resistant and works well in cold temps.
- Vinyl electrical tape is durable and waterproof.
- Vinyl electrical tape is best for enclosed mechanical and electrical scenarios.
- Vinyl electrical tape doesn’t take abuse as well as PVC.
- Vinyl electrical tape is not ideal for cold temps.
- PVC electrical tape is often more expensive than vinyl versions.
Scotch Electrical Tape
Scotch electrical tape comes in a wide variety of versions, although two of the most popular are their Super 33+ and Super 88 models.
Both options feature polyvinyl chloride (PVC) backing and a pressure-sensitive, rubber-based adhesive that delivers moisture-free, corrosion-resistant protection. However, there are a couple of differences between the two:
- Super 33+ – 7-mil thickness, rated for indoor use (not all-weather), not UL listed.
- Super 88 – 8.5-mil thickness, indoor and outdoor applications, rated for all-weather use, UL listed, and CSA certified.
- Both versions are ideal for the final layer of a three-tape splice.
- Super 33 is rated for indoor use.
- Super 88 is UL listed, and CSA certified.
- Super 88 is available in 8.5-mil versions and can work for outdoor applications.
- Super 33+ is not rated for outdoor use, isn’t UL listed, and is only available in a thinner 7-mil version.
Liquid Electrical Tape
Compared to traditional versions, liquid electrical tape is basically rubber in a fluid form, which you apply to wires using a built-in brush. Although it’s a fluid, liquid electrical tape delivers abrasion, damage, and moisture resistance, and is also an excellent insulator.
Because of its properties, liquid electrical tape is ideal for a wide variety of jobs, whether around the house, outside, or even on your boat.
- Easy to apply using the built-in brush.
- Provides many of the same features of traditional electrical tape.
- It also delivers abrasion, damage, and moisture resistance.
- It can withstand more extreme temps than vinyl tape.
- Wide variety of uses outside of electrical.
- Competitive price.
- It takes a few minutes to dry before you can apply another coat.
Electrical Tape Grade
Not all electrical tape is constructed the same. Instead, different grades deliver different performance attributes for backing construction, thickness, and dielectric strength (i.e., an insulation’s maximum acceptable voltage).
For example, top-notch electrical tape is made from higher-mil PVC and vinyl, making it extra resistant to abrasion and corrosion. When it comes to backing construction, lower-grade tape will also typically be monomeric versus polymeric.
Monomeric vs. Polymeric Electrical Tape
When shopping around for traditional electrical tape, you’ll encounter two main types:
- Monomeric – A lower-grade tape manufactured using short-chain plasticizers, which is ideal for light-duty, general-purpose jobs. Its adhesion tends to degrade with time. Tends to be competitively priced.
- Polymeric – A high-grade tape manufactured using long-chain plasticizers that deliver tighter seals, more outstanding durability, and boosted corrosion protections. Polymeric tapes are often made using thicker-gauge rubberized plastic as well. But keep in mind that higher quality often translates into higher prices.
How to Use Electrical Tape
Using electrical tape isn’t rocket science, but it can take some trial-and-error before getting the process down pat. Here’s a quick outline of how it works:
- Hold the tape’s tip with one hand and the rest of the roll in the other.
- Put the tape on the surface you want to wrap.
- Pull the tape taut to 75% of its width to the point just before it breaks.
- Loop the tape once around the wire, overlapping the layer underneath.
- Proceed to wrap the wire, overlapping each previous layer by half an inch, while continuing to stretch the tape so that it better conforms to the surface.
- Continue wrapping up and down the wire until the tape is thicker than the wire’s insulation.
Remember that no matter how good your tape-wrapping skills are, you should never use electrical tape as a permanent connection insulator. Instead, use wire nuts.
Grounding and Insulation
A wire’s insulation is non-conductive material – usually silicone, PTFE, nylon, TPR, or PVC – that surrounds it and resists its electrical current.
On the other hand, a grounding wire is a safety wire that doesn’t carry an electrical circuit until a short or other dangerous situation arises. Once it happens, the current is “grounded” by the earth, which naturally carries a negative charge.
In either instance, electrical tape is an indispensable tool for sheathing your connections, covering other exposed wires, and keeping everything safe.
Suppose you need to label various wires from the junction box to their terminating point. In that case, different colored pieces of electrical tape, along with a fine-tipped marker, can work wonders for organization.
For example, you could place yellow pieces of electrical tape, labeled appropriately, at either end of the circuit running from your junction box to your bathroom. Or, you could mark both ends of the wire from your junction box to your HVAC system.
Remember that labeling wires with electrical tape is just one of dozens of solutions, including masking tape, pre-marked labels, and plastic clips.
Also, make sure that you don’t accidentally cover any exposed wire at either end with electrical tape, which could cause a red flag during an inspection.
Making Minor Repairs
While the Federal OSHA electrical safety standards officially frown upon the practice, electricians often use electrical tape to make minor repairs to a frayed or damaged wire.
Basically, in these instances, the electrical tape acts as a replacement for damaged insulation. Just keep in mind that, as with regular taping, the electrical tape should be thicker than the wire’s insulation.
Electrical Tape Uses by Color
Compared to the original version, you’ll find electrical tape in a wide variety of colors and recommended uses, including:
- Black – Used for insulation and low-voltage applications;
- Green – Used for earth grounds;
- Green w/Yellow Stripe – Used for an isolated earth ground;
- Blue – Used for low-voltage and phase C applications;
- Orange – Used for low-voltage and phase C applications;
- Purple/Violet – Used for high-voltage and phase B applications;
- Brown – Used for high-voltage and phase A applications;
- White – Used for low-voltage and neutral applications;
- Red – Used for low-voltage and phase B applications;
- Yellow – Used for high-voltage and phase C applications;
- Gray – Used for high-voltage and neutral applications;
You’ll also find assorted packages of electrical tape, which often feature a combination of colors.
Considerations for Choosing the Best Electrical Tape
There are many factors to consider when selecting suitable electrical tape for the job. Here, we’ll outline some of the most common, such as ease of use, stretch, and strength, as well as how they can apply to you.
Ease of Use
Imagine that you’re in a hot attic, wrapping electrical tape to a final connection before heading out for the weekend. But the extra-strength tape you purchased isn’t easy to tear, so you have to expend extra energy and wrestle with it for several minutes before it frees itself.
A similar scenario could occur with the tape’s stickiness and ease (or lack thereof) when unrolling.
What can you do? When shopping around, look for electrical tape advertised as “easy-on” or similar phrasing. It still might take some time to find your preferred brand, but this will at least get you started in the right direction.
Elasticity is one of the most essential traits for electrical tape since this is what allows it to conform to different surfaces and stick to itself while you’re wrapping. Therefore, the longer tape can stretch before breaking, the easier it will be for you to do the job right.
While rubber-based electrical tape might not exactly return to its original shape after being stretched to the max, it will continue contracting on itself after installation for an even better connection.
Here’s how to quickly test elasticity: wrap the tape around one of your fingers like you would a wire. If you feel an immediate tightening, that’s a good sign. You can also place an end on a table, pull the tape out, and watch how closely it returns to its original shape.
Just like any other tool, your electrical tape needs to hold up to different elements and conditions, including:
- Chemical and harsh fluids – Oils, acids, and degreasers found in everything from pressure washers to rust-removers. Standard electrical tape should work well.
- Abrasions and punctures – pulling wire isn’t an easy process for you or your tape. We’d recommend looking for models that are abrasion and puncture resistant. Extra-thick tape (greater than 7-mil) can deliver in these instances.
- Moisture and water – Wiring is rarely located in comfortable, well-ventilated, or air-conditioned areas, so you’ll want a tape that can resist moisture and water. This factor is crucial for outdoor applications. Most electrical tapes are at least water-resistant, while some are advertised as waterproof.
- Extreme vibrations – Wiring near machinery or HVAC systems can be subjected to extreme vibrations. Look for thick rubber electrical tape.
- High-voltage – For high-voltage scenarios, you’ll want to look for self-sealing (also known as self-adhering) electrical tape.
- High-temperature performance – Wiring’s rarely located in comfortable, well-ventilated, or air-conditioned areas, so your tape needs to hold up to temps at both ends of the spectrum. Look for electrical tape advertised as high-temperature or flame-resistant.
- Airborne contaminants – Indoor and outdoor pollutants, both biological and chemical, can slowly wear down your electrical tape if you use the wrong one for the job.
As an electrician, there are hundreds of codes that you need to keep in mind while working. When it comes to electrical tape, premium models often feature one of the following designations:
- UL Listed – Underwriters Laboratory (UL) listed electrical tape typically comes with a higher rating for adhesion, voltage, fire, and weather resistance, along with failure points,
- CSA Approved – The CSA Group independently tests and certifies different products, including electrical tape, against recognized standards for safety or performance.
Attaining UL listing or CSA approval is a badge of honor, so in most instances, manufacturers will advertise this about their electrical tape.
Strength and Width
In most instances, standard electrical tape will adhere to its surface for about five years. However, depending on the tape’s exposure to extreme temperatures, stress and abuse, and UV exposure, this time can be cut meaningfully shorter.
Once electrical tape begins breaking down, its grip will loosen. If exposed to lots of vibration, this can cause the tape to move enough so that wires are left exposed, thereby creating a fire hazard. In other words, you’ll want to focus on models that promise to deliver excellent adhesion.
When it comes to width, wider electrical tape is generally more difficult to tear than thinner versions, but it also delivers more surface area and a potentially firmer grip. On the other hand, if you’re working in tight spaces or with smaller wires, the thinner traditional electrical tape should deliver what you need.