Top 4 Things to Consider Before Buying UV Blacklights

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UV blacklights are great devices with a wide range of applications in the arts, industry, and scientific research. Unlike regular white light bulbs, UV blacklights are unique in that they primarily emit ultraviolet radiation as opposed to visible light, and as a result, there are some additional factors you will want to consider before making a purchase.

Blacklights are most commonly used when the fluorescence of objects needs to be observed, with as little visible light as possible. Generally, this means that a blacklight will emit primarily UV-A radiation, and very little visible light. Below, we discuss 4 questions you should consider before purchasing a UV blacklight.

WARNING: Always use common sense and observe safety around the use of UV lights. The amount and intensity of UV-A light energy emitted by blacklights is generally below dangerous levels, but be aware that the UV light energy emitted by the lamps is invisible. Do not, for example, look directly into a UV LED blacklight when it is turned on, even if it does not appear bright. It may not appear like much, but the dim light you see is just a small fraction of the actual UV light energy hitting your eyes.

1) Which Ultraviolet Blacklight Lighting Technology is Best?

For most applications and installations, UV blacklights are available either as a fluorescent lamp or an LED light. Until recently, fluorescent lamp blacklights were the primary option, but with rapid advances in LED technology, UV LED lights are quickly becoming the preferred option.

Some advantages of UV LED blacklights include:

  • Higher efficiency - UV LED lights are typically 1.5x - 3.0x more efficient than fluorescent UV blacklights

  • Longer lifetimes - UV LED lights last for 25,000 hours or more, and do not "burn out" like a fluorescent lamp - their UV light output gradually diminishes over time. Fluorescent blacklights typically last only 5000 hours and fail catastrophically.

  • No mercury or hazardous materials - UV LEDs do not have any mercury or other hazardous materials that are commonly present in fluorescent lamps. As a result, you won't need to worry about accidentally breaking a UV LED lamp and have to do any special handling of the cleanup.

Fluorescent blacklights can oftentimes be cheaper than an LED blacklight, so if you're on a tight budget, fluorescent UV blacklights might be the way to go, especially for short-term use. Don't forget to consider, however, the lifetime and efficiencies in any cost of ownership calculations.

2) How Much UV Do I Need?

UV blacklight "brightness" is a difficult metric to describe, because UV light energy is not directly visible. Although lumens is typically the metric used to measure the amount of visible light, because ultraviolet light is invisible, this metric is essentially useless. For UV lights, the most accurate metric is "watts" of UV light output.

What is a "watt" of UV light? Watts are simply units of energy, and as you may recall from your introductory physics classes, energy can exist in a variety of forms - for example, electrical, kinetic, chemical, or light energy. In this case, we are measuring the amount of light energy emitted in the UV wavelengths.

For most basic applications, 1 watt of UV light energy output is sufficient to create strong fluorescence effects over a 100 sq ft area. For a 200 sq ft area, simply multiply the target UV levels by 2x for an estimated 2 watts of UV light energy needed.

IMPORTANT: electrical watts does not equal UV light watts! As with regular household light bulbs (e.g. 60 Watts), we are most accustomed to describing UV light bulb power in terms of its electrical energy consumption. But as is the case with household light bulbs, what matters most is the amount of light energy produced.

Unfortunately, most manufacturers do not list the UV light output, and instead simply indicate the electrical watts input. For example, you may find a product described as a 40 Watt UV blacklight, but unfortunately all this means is that the lamp consumes 40 watts of electrical energy - this does not provide us with any information about its efficiency, and how much actual UV light energy is produced. It could be a great, efficient light emitting 10 watts of UV (25% efficiency), or a terrible light with 1 watt of UV (2.5%) - we just don't know from the 40 watts power consumption alone.

If a product lists the amount of UV light output in watts, you can use this value directly to estimate your UV light needs for a space. If not, you may have to use some rough efficiency estimates.

As a rough ballpark estimate, fluorescent blacklights have an efficiency value of 5-15%. In other words, for every 100 Watts of electrical energy consumed, the blacklight will emit 5-15W of useful UV light energy.

UV LED blacklights, on the other hand, have improved efficiency values of 15-25%. For the same 100 Watts of electrical energy consumed, UV LEDs will emit 15-25W of useful UV light energy.

Because efficiency values can vary significantly depending on the quality and design of UV blacklights, try to stick with products for which you can find the actual UV light output values indicated on a product's specifications sheet. If you do want to proceed without this data, you may want to use 20% as a rough estimate for UV LED efficiency, and 10% for fluorescent blacklight efficiency.

Below is a quick lookup table based on efficiency estimates of 20% and 10% for UV LEDs and fluorescent blacklights. Keep in mind that these efficiency estimates are ballpark estimates only, and individual products can vary in their actual efficiency values.


Below are two examples for determining how much UV light you need:

Example 1: How many feet of realUV 395 nm LED Strips for a 200 sqft area?

We first note that the UV output for the product is 0.9 watts per foot. Based on our estimated UV light needs of 1 W per 100 sqft, we determine that we will need 2 W for our 200 sqft area (multiply by 2x).

Dividing 2 watts by 0.9 watts per foot gives us 2.2 ft.

Therefore, our estimated realUV LED strip length needs is approximately 2.2 ft.

Example 2: How many 20W UV Fluorescent Blacklight bulbs  are needed for a 400 sqft room?

For this example, we assume we do not know the efficiency value of the fluorescent UV bulbs.So, based on our rough estimate of 10%, we will estimate 2 watts of UV light output per blacklight bulb.

Our recommendation for a 100 sqft area is 1W, so you will likely want anywhere between 2-3 of these fluorescent UV blacklight bulbs that each emit 2 watts of UV, to get the UV lighting effect you are looking for in a 400 sqft area.

3) Which Wavelengths of UV Do I Need?

Ultraviolet light encompasses a wide range of wavelengths, but most blacklight applications utilize a narrow range of ultraviolet radiation (UV-A) to produce fluorescence effects - specifically between 350 and 400 nm (nanometers).

But even within the 350-400 nm range, different wavelengths can create stronger or weaker fluorescence effects. As the chart below shows, most fluorescence is strongest in the 320-380 nm range, with a peak at 365 nm.


Therefore, we would typically recommend a wavelength of 365 nm for most blacklight applications where maximum fluorescence is desired.

However, there are some reasons you may want to choose another wavelength. For UV LEDs, the general rule is that the shorter the wavelength, the higher the price. 395 nm UV LEDs, for example, are a common and relatively affordable option that provides decent levels of fluorescence at a more affordable price point.

The downside to these longer wavelengths is that you will likely observe lower fluorescent effects, and you may also see some more visible "dark purple" light. A common phenomenon observed is a purple shadow cast by objects - a true 365 nm blacklight would be invisible, and therefore not cast any shadows.

Typically, light above 400 nm is considered violet light - i.e. visible light that has a deep purple color, so 395 nm is the longest wavelength option you should consider for a blacklight application.

A quick way to determine how much (undesirable) visible light is being emitted by the blacklight is to find its luminous efficacy, which is expressed in lumens per watt. All else equal, a UV black light with a luminous efficacy of less than 0.5 lumens per watt is best. You can typically find luminous efficacy values listed in the photometric test reports of blacklight products.


What does 0.5 lumens per watt signify? Lumens is a measure of brightness, used to measure light output in standard white lights. A 40 watt incandescent bulb emits 450 lumens. Therefore, 0.5 lumens per watt means that half a lumen will be emitted for every 1 watt of electrical energy consumed.

As a concrete example: a 10 watt UV blacklight emitting 0.5 lumens per watt will emit 5 lumens of visible light - approximately 1% of the brightness of a 40 watt incandescent bulb.



Be aware that many products will not explicitly list the wavelength of UV used, or if is, it is commonly hidden in small text, where you will find out that it may be 400 or even 405 nm. These wavelengths are easier and lower cost to manufacture, and result in weaker or even nonexistent fluorescence effects than 395 nm blacklights.


4) What Type of UV Light Fixtures Should I Use?

Finally, when choosing a UV light fixture, you should know that they can come in a variety of shapes and forms. Below, we've listed several examples and situations where they could be useful.

UV LED Strip Light

One of the most versatile form factors is a UV LED flexible strip. The LED strip consists of many ultraviolet LEDs (365 or 395 nm) mounted on a flexible circuitboard approximately half an inch in width.

The LED strips can be cut to length in 1-inch intervals, meaning you can install these in tight spaces such as photoboxes and display cabinets. Best of all, because they operate on very low voltage 12V DC, there is virtually no electrical or fire risk.

The backside of the LED flexible strip includes a double-sided adhesive material that can be used to apply to LED strip to virtually any surface.

Because the LED strip is flexible, it can even be installed on curved or uneven places.

Purchase Waveform Lighting's realUV LED strips here.

Rigid UV LED Light Bar

Rigid UV LED light bars are similar to the LED strips, but are better suited for more permanent installations, or those requiring more robustness. They are typically available in 1, 2, or 4 ft lengths, and can be daisy chained for simplified installation.

Rigid UV LED light bars are well suited for installation on trusses, shelves, or cabinets, where the light can be installed on a straight and flat surface.

UV LED Wall Washers

Wall washer UV blacklights are designed to cover a wall surface with UV light, either to illuminate objects with fluroescence on the wall (e.g. fluorescent wall art), or to allow the UV light to "bounce off" of the wall and reflect into the entire room.

Most wall washers come in 2 to 4 ft lengths, and are designed to be mounted into the floor. The lamp itself can be adjusted so that the UV light energy can be directed at the specific angles required.

Wall washers are great for semi-permanent installations such as bars, nightclubs and event spaces where covering large, vertical surfaces is needed. Alternatively, they can be used to reflect the UV light from the wall and into the rest of the space. One of the big advantages of this approach is that it allows the UV light to disperse, creating a very even distribution of light energy. Keep in mind that you may lose some UV light energy in this process, so you may need a little extra UV light in your wattage calculations above.


UV LED Flood Lights

As its name suggests, UV flood lights are great when needing to "flood"  a large area with UV light. Similar to wall-washers, these fixtures typically include the ability to adjust the angle of the UV light.

Most UV flood lights are also designed for outdoor use, so for any outdoor applications requiring fluorescence, these lights are a great option. Got outdoor events and parties with fluorescent objects? Or looking to incorporate some fluorescent architectural or landscaping features? The outdoor UV LED flood will be sure to be a great fit.

When installing these flood lights, be sure to install multiple lights from multiple angles, as this will help prevent "UV shadows" where some areas don't receive enough UV light energy to produce fluorescence due to objects blocking the UV light.

Purchase UV LED flood lights here

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