Cannabis and UVB

By Bokske - Own work, CC BY-SA 3.0,
Cluster of female cannabis flowers
You’ve probably found yourself here because you’ve heard that ultraviolet might increase the potency of cannabis. You might have also have heard some people say it isn’t true, and you are curious as to whether or not it really does. The purpose of this article is provide you some information, and some citations demonstrating the concept and why it really works and works extremely well if you do it right. The science behind the idea dates back to the 1980s and perhaps earlier, so this is a summary of that research. Much of this might be a bit of an oversimplification, but the goal is to give you an overview of why proper UV works, it isn’t to be a science class.

When we talk about ultraviolet and increased potency in cannabis, we are singularly talking about THC (Tetrahydrocannabinol) production. The effect of UV on the other 84+ cannabinoids isn’t fully known, nor has it been studied in detail. One would assume that if you increase the amount of THC, you are probably lowerin the amount of other cannabinoids (in particular, CBD or Cannabidiol), but this is just conjecture and the adecdotal evidence is conficting. Growers who are trying to produce marijuana that is moderate or low in THC but high in CBD would actually want to avoid ultraviolet, which explains why it is always grown in greenhouses (whose glass filters out all of the UVB and most of the UVA). Most growers, however, are wanting to grow cannabis that is high in THC, whether it is for medicinal use or recreational use. This article applies to them.

Understanding the plant

Most plants on the planet have both male and female flowers, making them hermaphrodites (monoecious). Cannabis is one of the rare plants that has individual genders, both male and female plants (dioecious[4]), although some plants will have both male and female flowers. The female is the grower’s target, and growing largest and most potent flowers (buds) is the goal. To this end, all males are removed, to prevent the female from going to seed. The key is, no one has told the female that she will never be pollenated. As far as the female plant is concerned, her flowers/buds are the bed for her children (seeds) and she simply hasn’t been pollenated yet. Her seeds are the only way she can reproduce, and reproducing is the primary purpose of every plant. As such, she will protect that flower as if it has her children in it, even before it does. Like most plants, cannabis has built in protection mechanisms to guarantee the next generations, which takes us to THC.

That THC is psychoactive is perhaps an accident. This quality hasn’t necessarily benefitted the plant, except those qualities has insured that man has cultivated the plant for thousands of years. THC has a biological role for the female plant that is critical for you to understand: THC has very high UVB absorption rates, meaning it is like sunblock for the plant.[1][2][3]


The ultraviolet spectrum is broken into three bands. They are actually “colors”, we just can’t see them. Like colors, there is a range within each color. This is how “pink” and “burgandy” are both types of red, just different parts of the red spectrum. The same for ultraviolet. If you look at a rainbow, you see the colors go from deep red (wavelength of 700nm) all the way to violet (400nm). The next color is UVA (320nm-400nm), then UVB (280nm-320nm) and finally UVC (10nm-280nm or 100nm-280nm, depending on who you ask). UVC is used for water purification and such because it kills organisms. It can also give you a flash burn in a few seconds, so fortunately, the atmosphere filters out almost all of it. When a plant is outside, they get a fair amount of UVA and UVB, typically in a ratio that is around 5% UVB and 95% UVA. They have evolved over millenia to adapt to this and survive. In the case of cannabis, the plant developed THC to protect the next generation. The more UV it is exposed to (to a point), the more THC it will produce.

When we moved growing cannabis to the indoors and in greenhouses, we did remove a lot of dangers to the plant: wind, soaking rains, animals, most insects and more. This increased the yield by 100% or more. The problem is that high pressure sodium (HPS) has zero UV of any kind. Metal halides have .5%, which is a negligible amount. The plants grow well, they are large, thick, robust and even potent, but they are far below their potential because we made their environment TOO perfect. Without the stress of UV, they have no need to shift resources into producing high amounts of THC. Instead, they produce a default amount, programmed by their DNA.

The process

In order to increase the THC, you need to understand that plants aren’t lazy. They spend all their time doing something: growing tall, growing buds, creating THC, moving nutrients around and such. When you introduce the proper spectrum of UV to the plant, you are forcing it to shift its resources into protecting itself. It will spend a little less time growing sun leaves, sugar leaves and even the buds will be more dense and just a hair smaller, but it will produce a lot more THC. Since THC is the ultimate goal, the market potential is significantly higher for plants grown with proper UV. It short, it makes you a LOT more money.

Using proper UV can cost you $5 to $10 per plant when you average out the cost of lights and fixtures. It is very cheap. Most people are able to get increases of 20% THC the first time they use it. Most experienced growers are getting over 30% more THC than with clones that aren’t getting UV. These aren’t guesses, our dispensory and grower customers report back to us with actual lab results, using actual control growing methods. Anyone who tells you they didn’t get more THC is probably using a reptile light or some similar underpowered UV source. Just as you can’t use regular screw in light bulbs to grow robust plants, you can’t expect high THC returns with weak UV sources. Ironically, the bad UV lights cost about the same as the good ones, it is just a matter of using the right lamps, the right way. And it is pretty easy IF you know how. With our standard 4 foot bulbs (Universal UV and the SG-1-40) you will use four bulbs for every 1000w (or equivalent) hood you have. Newer lamps in testing will cut that in half.

Proper usage

The key is giving the plants as much or more UV, in the right spectrum, than they would get if they were outdoors. In fact, you want to give them as much as they can take without being damaged. This means light on each and every bud, at least every other day. Typically, you would run the UV lights for your full light cycle, around 12 hours, as soon as you go into flowering mode or even earlier.

It takes more than just random UVB. We have found certain frequencies of UVB make the plant react more vigorously than others. We have reason to believe that UVA is also beneficial. While it doesn’t stimulate THC production, it penetrates much more deeply than UVB and may stimulated trichome production, which makes THC possible. This is why we have UVB lights with multiple “soft” peaks at the right frequencies, as well as strong UVA output in exactly the same part of the spectrum that the sun is strongest at. This gives you a sun-like glass tube that you control.


So does it work? Unquestionably it works as long as you use the right power level and right frequencies, and the pay off is often 100x the investment. This is huge. This is also why many growers are using our lamps, and why many growers don’t let anyone know that they are using our lamps: They don’t want anyone to know their secret, why they get the big bucks, why they have the best product. Of course, it still takes good light, good water and soil, good care and air, and proper technique, but UV light is just as important as those other things if you are after premium results.


1) * Pate, David W. (1983). “Possible role of ultraviolet radiation in evolution of Cannabis chemotypes”. Economic Botany 37 (4): 396–405. doi:10.1007/BF02904200
2) * Lydon, John; Teramura, Alan H. (1987). “Photochemical decomposition of cannabidiol in its resin base”. Phytochemistry 26 (4): 1216–1217. doi:10.1016/S0031-9422(00)82388-2
3) * Lydon J, Teramura AH, Coffman CB (1987). “UV-B radiation effects on photosynthesis, growth and cannabinoid production of two Cannabis sativa chemotypes”. Photochemistry and Photobiology 46 (2): 201–206. doi:10.1111/j.1751-1097.1987.tb04757.x. PMID 3628508
4) * Beentje, Henk (2010). The Kew Plant Glossary. Richmond, Surrey: Royal Botanic Gardens, Kew. ISBN 978-1-84246-422-9
5) *
*) Help locating some sources came from

Dennis Brown

Confused? We are working even harder to make it easier

I’ve been working on a new page to help in picking the right lamp. There are so many applications for each lamp, it is pretty easy to get confused, so trust me, I understand. This is compounded by the fact that we make our lamps able to run on many different wattages, letting you get the most power of of them, so matching then with ballasts can be confusing. Click on that new link above if you have questions, I think it helps narrow it down for you some.


2015 – Looking back

It has been a great year for Solacure. While our roots go to back to 1985, designing and building UV lamps for the cosmetic market, Solacure as a stand alone company has been open just under two years, and already we have been able to find new markets, new uses for UV lamps. These range from growing cannabis, to building violins and guitars, and now Audeze is working with us to make the world’s best headphones even more beautiful.

All and all, we can’t complain and we won’t. There is still a lot of work to do, lots of research to complete, new things to invent, and new uses waiting around the corner. As we end 2015, I just want to say THANK YOU to all our customers. Solacure isn’t a mega-corporation, we are a privately held company that builds our customer base one phone call at a time, one customer at a time. Some of our customers are huge corporations, some are just hobbyists, toiling away in their basement for the sheer fun of it. Most are small business owners, such as luthiers or craftsmen, looking for a better way to make a better product, and they come to us for help. Each customer matters to us. You are why we do everything we do.

I want to wish you all a wonderful and happy New Year, and I look forward to having fun, designing new things, and helping you realize your own dreams in 2016.


Dennis Brown
Owner, Solacure LLC

Brookhaven National Labs

brookhavenHad some interesting discussions with a gent from the Brookhaven Nation Labs, which is part of the US government’s Department of Energy. Super Collider type stuff. Anyway, they are testing with Solacure lamps now, for clarifying leaded glass. A new use for us, but it just goes to show, anything you can do with ultraviolet, you can do it with Solacure lamps. Next step is building a giant platform so they can do this in place without having to move tons of glass.


If you go cheap, you might as well stay home

Can’t I just buy one bulb and put it a few feet away?

I get this question a lot, surprisingly. People don’t want to buy a $5000 to $10,000 curing rig, but also don’t want to spend $100. You have to be realistic when you are designing a curing rig, and be willing to spent at least a little money or you won’t get the results you want. Most curing rigs needs 4 to 16 lights, meaning a cost of $280 to $1000, but this includes the lamps, ballasts and lamp holders. it can be done a little cheaper if you use off the shelf fixtures, which will be slower, but still work. Where you don’t want to skimp is the number of lamps you use, because that affects more than time, it affects quality of cure.

You can buy twelve Solacure Curall curing lamps for $360, power it with $180 worth of F32 fixtures from Home Depot, and have one hell of a rig. It won’t be super fast, but it will be fast enough, and for under $600 have a rig that will cover guitar bodies, or necks, or violins. Or for $200 you have a rig for curing pool cues or fishing lures. For another $100-$200, you can have one that does it industrial speed and has twice the life of the regular lamps. You don’t have spend thousands, but you have to be willing to spend a few hundred if you want a serious curing rig fit for at least part time use.

When you cure an item, you need enough lamps that it effectively covers the entire item. Let me give you an example using the easiest thing in the world to cure, a 2ft x 2ft flat piece of material. If you use one bulb, you would have to be about 2 feet from the item in order to have any semblance of even coverage, meaning the ends are about as far away as the middle. Using the Pythagorean Theorem, that puts us at about 2.25 feet away from the edges and 2 foot from the center, a difference of about 12%, which is acceptable. Any lower, and the reflector will prevent the edges from getting much of any light, so the middle cures, but it fades out to the ends, which won’t cure at all.

Let’s compare this with an optimum distance of 3 inches away. Using the Inverse Square Law, this means that the amount of light hitting any cubic inch of board at 2 feet vs 3 inches, gets 1/64th as much power. Yes, it takes 64x longer to cure. A 3 to 5 minute cure is now 192 to 320 minutes. Three to five hours. Going cheap and using 4 lamps would let us do this cure in about 10-15 minutes (see notes below), using 8 lamps and we are back to our 3 to 5 minute range. It is fine to go cheap, but if you go too cheap, you shoot yourself in the foot.

Generally speaking, you can keep your project as close to the lamps as the lamps are apart. Lamps that are 6 inches apart can support having the project 6 inches from the lamps. Going over 6 inches means you quickly and radically decrease the effective power, and enter the realm of wasting your time.

It is better to use more lamps in cheap fixtures than it is to have just a couple of lamps in high output fixtures. The total number of lamps is more important than the wattage you put to each lamp. It might not be intuitive or obvious at first sight, but trust me, this has been tested over and over again. Most of my testing is done with 6 to 8 lamps run in lower power mode, simply to show what you can do at the lowest power level, and I’ve tested UV lamps for curing more than anyone I know. The more sources of UV, the better, every time. The smaller the distance to the UV source, the better, every time.

So if you have to skimp, skimp on the power and don’t skimp on the number of lamps. This will guarantee you have the best coverage, even coverage that will let your project cure evenly, without any wierd artifacts. It will also let you put the lamps closer and guarantee a cure time that is much easier to live with.


Notes: 4 lamps at 7 inches apart covers the area, 7 inches from the material is just over twice, so the power is reduced by 80%, but you have overlamp from other lamps (compounding the Inverse Square Law) so you end up closer to 50% to 60% of the original power per square inch, thus 10-15 minutes). The Inverse Square Law is based on a single point of light, and the mathemetics get exponentially complicated as you add sources of light, to the point of no longer being applicable, if you add enough lights. If you are turning the item in front of a flat panel of lamps, the math also gets tricky, but distance is still your enemy.