With the onset and spread of SARS-CoV-2 virus and the COVID19 it causes, I have seen many offer up the idea of using low cost UV light sources used primarily for curing resins and/or finger nail polish, as a method for sterilizing surfaces and used masks. Cutting to the chase… a $35 nail salon cure light is not going to work.

These sources use light between 365nm and 405nm, depending on the intended application. This is considered long wavelength UV light, or UVA (315 to 400nm). While these may be somewhat effective against some bacterial invasions, with extremely long exposures and/or very high intensity levels (well beyond those of a small cure light), there is no evidence this is a reliable sterilization solution for viruses.

To kill viruses, hospitals are now using UVlight robots that emit high levels of UVC radiation between 200nm and 280nm, and the primary germicidal range for UVC is between 254nm and 260nm, for periods of around 20 to 30 minutes – on top of chemical cleaning and sterilization procedures. The reason they use robots, is that this radiation is dangerous to human occupants, so is not done when anyone is in the room. UVC disrupts the DNA and RNA of micro-organisms, which prevents them from reproducing. Read Here for more on these machines and their use.

Note that while UVC radiation is being applied in the fight against viral contamination on surfaces, it is not used alone. Chemical disinfection is often used in concert with UVC light, as this does more than disrupt DNA/RNA, it kills the micro-organisms, and wipes them away.

While there is evidence that narrow spectrum UVC light, between 207nm and 222nm, which cannot penetrate skin, is as effective as any other UVC source, finding such sources is somewhat difficult, and the risk of failure (from dangerous UVC light exposure) enough of a concern, that this may not be a practical solution – yet.

Light in the 365nm to 400nm range used on cheap cure lights is not going to destroy a virus, or disrupt its DNA, or remove it. These are not going to do anything but provide a false sense of security that will potentially lead to exposure to the very infection one is attempting to protect oneself from.

Another issue with short wavelength UVC light, is its limited capacity to penetrate materials or reach beyond surfaces, particularly those used in surgical and N95 masks. For a $25 toothbrush sanitizer or $50 cell phone sterilizer, this is not a serious issue. With an exposure of between 6 and 10 minutes, UVC has been shown to reduce the presence of harmful micro-organisms on surfaces in these applications. However, using a cell phone sanitizer to sterilize a fabric mask has not been proven, nor is it recommended. If the light cannot penetrate the mask’s many layers and fibers, and underlying filter materials which trap organisms (their purpose), it is unlikely that any real effect will be realized.

For more on this topic,’Disrupting the Transmission of Influenza A: Face Masks and Ultraviolet Light as Control Measures‘ reveals that the combination of UVC light for disinfecting surfaces and equipment, combined with face masks, is effective in fighting Influenza A. However, this does not necessarily apply to SARS-CoV-2 or COVID19, nor was it suggested that UVC was a viable strategy for sterilizing face masks.

There are no recommendations for disinfecting face masks using UV light to protect a user from being infected. In fact, the FDA states that surgical masks and N95 masks are not recommended for public use to protect from infection. Broad miss-use does not change this reality. While trained hospital staff may be able to rely on the N95 mask for some exposures, frequently used in conjunction with face shields, applied expertly, to protect themselves from infection. The general public has none of these qualifications.

If the masks are improperly cared for, or treated to ineffective disinfection processes, the result may be more harmful than having nothing at all. Think about this: The purpose of the mask is to capture micro-organisms and hold them on the surface and within the filter media. If that is contacted during mask removal, and the hand or finger touches an eye, or a lip, the virus has been given the free ride it was looking for – those warm and moist mucus membranes. Wave that soiled mask around a little as you remove and store it, and a few of those micro-organisms escape, and fly, then fall on surfaces around you. Now, handle that mask even more to insert it into a make-shift UV light box, and the exposure sequence continues. Take that same soiled mask, after inadequate treatment (still filled with bugs), and put it back on… get the picture? For the general public, the mask may act more like a bug collection devise for dispersion at home – than an actual protective device.

That said, there is one process that has been FDA approved for limited use (state of Ohio at this moment), which uses Vapor Phase Hydrogen Peroxide by Battelle CCDS to sterilize used N95 masks without reducing filter efficiency. This cannot be done at home.

The only known strategy for protecting oneself from being infected, is distancing oneself from others, either through isolation or active distancing, plus careful and diligent hygiene (hand washing, avoiding contacting surfaces of unknown exposure, and avoiding touching the face, particularly eyes, nose and mouth.

I offer this only to help those who might believe themselves safer through home baked solutions that actually produce higher risk of infection. Please, be safe, and be well.


In addition to the exploration above, I found this at the SAGES (SOCIETY OF AMERICAN GASTROINTESTINAL AND ENDOSCOPIC SURGEONS) . This is an article on the topic of re-using N95 masks, that specifically states that use of UV light renders them unusable. Further, it states that all contact with metal must be avoided. It specifically states:

When sterilizing N95 masks, be wary of using UV light–keep N95 masks away from UV light / sunlight. N95 masks are degraded by UV light because it damages the electrostatic charges in the polypropylene material. It is unclear how long the masks can be exposed to UV light before they are ineffective.

It re-iterates this again:

Keep N95 masks away from UV light / sunlight.

That appears to indicate that use of UV light for disinfecting N95 masks with UV Light.

The Delaware Health and Social Services has issued guidlines for use of surgical masks, which is also worth looking at, for those concerned. They state:

• Using surgical masks will not fully protect you from being infected. Hand-washing, isolating infected
patients, and covering the mouth and nose when coughing also help to reduce to the risk of infection.
• Masks must be changed when they become wet with saliva or other bodily fluids, as they lose their
protective properties.
• Surgical masks are not tested against specific microorganisms and do not prevent specific diseases.
• Never reuse, wash or disinfect surgical masks.
• Never share surgical masks with others.
• Place used or soiled masks into a tied plastic bag to prevent dripping.
• Wash hands thoroughly with soap and running water, or use an alcohol-based hand gel after handling.

Please, be safe, and stay well, and most of all, stay informed. Small mistakes can be very costly when you are dealing with infectious micro-organisms.

A Common MacAdam Fail

Posted: May 24, 2019 in Uncategorized

The MacAdam ellipse is a Standard Deviation Color Matching (SDCM) protocol for describing visibility of human observers of differences of sources, by how far they deviate from a reference color. Each ellipse represents a standard deviation from the reference (center) source. It is generally accepted that within 3 MacAdam ellipses, most observers cannot discern a difference between two sources. At 4 steps, a significant sampling of observers would see a color difference. At 7, virtually everyone will see a difference. For a more complete background, there are numerous sources describing these details, such as https://en.wikipedia.org/wiki/MacAdam_ellipse. The shape of the ellipses varies by color, as human visual differentiation changes in both spectral sensitivity as well as range between sources.

With this, it would seem pretty straightforward that when someone claims their product, LED, or light sources fall within 2 or 3 steps, that it can be assumed that the difference between two sources from that provider will be unseen. Unfortunately, a common miss-interpretation and incorrect application of the MacAdam ellipse protocol creates an actual deviation that can be as much as double that stated. The illustration below shows how this happens. Read the rest of this entry »

The Adventure with Architectural SSL Magazine

In 2006, I pitched the idea of a magazine dedicated to Solid-State lighting technology as it applies directly to architecture with the owners of Construction Business Media. After a few pizza lunches and more convincing, they moved to creation of Architectural SSL magazine in time for Lightfair 2007 with its debut issue.

Since that debut 12 years ago, I have participated in editorial discussion and planning, contributed content to every issue with a market setting feature, a closing remarks Op Ed, white papers, judeged products, provided reviews of various products and provided general commentary on the progress of SSL into the lighting market. Read the rest of this entry »

Change of Plans and Direction

Posted: March 23, 2019 in Uncategorized


After significant evaluation of successes, personal goals, market direction, costs of operation, and future trends emerging – I have decided to make large scale changes to how we participate in the solid-state lighting market.

Pursuant to this, as of March 22, 2019, Lumenique, LLC has begun a complete overhaul/re-casting, starting with  the closing of our prototype and research facility in Menomonee Falls, WI effective immediately. This includes Tasca ending its 9-year pursuit of light cure products for curing fiberglass resins.

The principles of Lumenique, LLC/Tasca will be relocating to a new facility in Elgin Illinois, beginning mid- April. Until then, Lumenique is closed for business to focus on the monumental task of moving house and shop facilities. Both Angie and I can be reached by email and cell phone, should anyone wish to make contact, regardless of status of the business itself.

I will continue as Editor for Architectural SSL magazine and contributor to NZB magazine for Construction Business Media through the transition and beyond.

More details will be announced as things gel, and our new direction solidifies.


Kevin Willmorth 

Deals upon Deals!

Posted: March 19, 2019 in Uncategorized

We’re making changes and taking a fresh approach for spring. That means we have an assortment of items that are surplus to our changing requirements, so are offering them up for sale at mega-low prices. This includes test meters and lights alike. Everything is in good to excellent condition, some old, some new, no garbage in the lot. Our need to clear this inventory is your gain!

Take a look at the Tasca Store!

He who hesitates are lost! (applicable misquote from JosephAddison’s play Cato (1712)

There is a great deal of marketing noise professing the use of CCT white light tuning to enhance circadian function in work environments. The real question is whether this approach actually has any real-world effect on human response to light in the spaces it is being applied to.

Theoretically, the proposition is that by changing the CCT of light, one can affect circadian reaction – specifically increase or decrease melatonin suppression. The proponents of CCT tuning profess that, with no consideration of illuminance levels, cooler CCT’s will produce greater melatonin suppression, resulting in a more wakeful state, while warmer CCT’s will produce significantly less melatonin suppression, creating a more restful state that does not disrupt sleep cycles. The assumption is that illuminance levels required for proper task performance can be maintained, relying solely on a CCT change alone to impart the desired “Human Centric” benefit.

To test this, I created a test box that houses 5 different high CRI LEDs, with a dimmer. The CCT’s I chose are the popular 2700, 3000, 3500, 4000, and 5000K. All had >88CRI and >90Rf/94Rg (using TM30). The first test was to set illuminance at 50Fc, and measure the difference in Circadian Stimulus (RPI/LRC method), and Melanopic Lux (Well Buildings Standard). Read the rest of this entry »

Found the Timer

Posted: November 14, 2018 in Light Cure
Tags: ,

Update on the timer search:

While the response from the call-out here did not return anything from the lurking electronics gurus of the inter-webs, I was able to find a supplier here in the USA (Kentucky) able to make exactly what I needed. The company is called Curious Technology, and the individual that came up with the solution is Greg Cunningham.


The Timer

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