UV LED Lights and Measured Output for UV Cured Finishes (Osmo, Vestings, etc)

[luvmytoolz]

There's a great thread that was started on the exciting topic of UV Cured Hardwax Oil finishes at this link, specifically the Osmo LED Smart Oil:

S

Thread 'Osmo LED Smart Oil'

Jan 14, 2026

I figured to start a discussion on Osmo LED Smart Oil, the new almost-instant cure oil that can take the place of Osmo Polyx and Top Oil for interior finish. Unfortunately it's for professional use only due to safety regulations, but anyone with a business license can buy it.

The great benefit is that the oil has a long open time, and cures instantly after a couple passes of an expensive UV lamp—which means two coats and out the door in the same day.

The finish doesn't require an Osmo branded UV LED lamp, but if you want to go that direction, the light retails for about $1900. The oil...

• SitkaZach
• Replies: 35
• Forum: Finishing and Painting

• 

I've been getting into this myself with a different brand of Hardwax Oil and thought I'd start a new thread focussing on the hardware required so as to not stray the Osmo thread.

This video by Suman states you need 450mW/cm2 of UV Band A in the 395nm spectrum to fully cure the Hardwax Oil. The trouble is most UV light suppliers don't specify the combined rating of the output at a certain distance. And a LOT of sellers claim specs far exceeding the actual unit's capabilities. The details are around the 14 minute mark:



I started out using a UV Cured resin (not Hardwax Oil finish) to fill in resin voids on my charcuterie boards, but all efforts were fruitless. The first UV torch I had from somewhere unknown literally did nothing, a highly rated "Swiss Tech" torch that had good reviews was bought but seemed to take forever. I then bought a 100 LED torch off Ebay that claimed to be the goods but never really quite cured it despite long exposure times. A large LED panel from Temu was tried next and leaving it almost touching the board for several hours or so sort of cured it, while still leaving it feeling soft and very plasticky.

So as I was spending $270 on a 1L can of Vestings and didn't want to leave the results to chance, I bought a highly reviewed UV Radiometer from Linshang as I needed to commit to a possibly very expensive UV source if the cheap one ($225) I was also buying from Ali didn't stack up. This was well worth it and turned up some surprises.

Starting with the first one, holding it right against the meter nothing was registered so I'm guessing it's just a pretty purple light and not worthy of any pics.

The "Crappy" Ebay 100 LED torch was measured next, and above 20mm the meter barely registered anything, at 20mm and less it peaked at 7mW/cm2. A barely anything result.

The "Crappy" Temu 144 LED Panel was measured next, and at 10mm height the meter peaked at 7mW/cm2. Another barely anything result.

The Swiss Tech torch was next and produced really great results but with a major caveat. While it produced a very impressive 125mW/cm2, the actual working area of the beam as shown in the "Spread" pic is around 35mm diameter at 150mm distance. Moving away from the beam centre dropped to almost zero output. For small items you could work with a 35mm beam, but for boards, panels etc it's pretty much unusable.

I then measured the 40 LED 800W UV from Alipress:

UV-Lampe, 700 W, 800 W, UV-Härtungslampe, 365 nm, 395 nm, 405 nm, fluoreszierende Erkennung, schattenloser Kleber, grünes Ölharz, UV-Härtungslampe - AliExpress 39

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I was worried it would turn out to be crap, but it works a treat. At the UV Finish manufacturer's spec of 100-150mm distance, it put out a whopping 339mW/cm2. Testing has shown that 2-3 seconds per 300mm travel back and forth is more than enough to fully cure the resin. So aside from any possible faults developing, I'd heartily recommend this unit. It's quite robust too, and at 1/4 the cost of the cheapest recommended UV light source, but at least twice as powerful with a much larger UV spread, it's a bargain.

Just for curiosity, I also measured the UV output outdoors, we're in the middle of Summer in a fairly moderate Melb, at midday it peaked at 16mW/cm2, and late in the arvo it went up to 22mW/cm2. So you could cure the finishes outside, but it will obviously take some time longer.

 

[luvmytoolz]

Circled in red is the 40LED (8 x 5 array) 800W light I bought from Aliexpress, and couldn't be happier with the results and price. I'll probably buy the cheaper still but longer 10 x 4 LED array one as well for a spare.

To put out 73mW/cm2 at just under 2 feet height is pretty impressive.

 

[hdv]

Very interesting stuff!

Did you, by any chance, also test the output of the UV Beast torches Suman was using? I have one and for small items it seems to work OK. I once held my hand under it (not on purpose) and I felt it warming up immediately. Not that this says very much about the UV specific output, but it does seem to put some energy on the surface that it is shining on.

 

[luvmytoolz]

@hdv I don't have the UV Beast Torch myself, but Suman did actually measure it in his video at around 105mW/cm2, which is a little less than the Swiss Tech I tested, but the Beast does appear to suffer the same issue the Swiss Tech has, in that it has a very narrow focussed beam, and outside of this beam the UV light is of no benefit. The Swiss Tech however is about 1/3rd to 1/5th the cost of the Beast (depending on the model) while being more powerful with a single LED.

To be honest at the price the Beast is, if you were looking to buy a UV torch and unless you're only going to do small touch-up spots or similar, I think the ones on Ali are far better value, while being orders of magnitude better.

 

[luvmytoolz]

For those interested in buying a UV Radiometer, I spent some time researching models, and it ended up down to two models that were the most affordable whilst having good reviews and performance.

The Solarmeter 4.0 is the one Suman uses and is a highly regarded work horse, but would have set me back around $500 as it's hard to get here in Oz.

The other highly rated ones were the Linshang models, with the LS137 model the most economical I found.

UV-Energiemessgerät, Radiometer, UVA-LED-Lichtquellen, LS137, Messung von Energie, Leistung und Temperatur, ultrakleine Größe, hohe Präzision - AliExpress 1420

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I bought this direct from Linshang's shop on Ali, and I'm really happy with this meter and think it's worth every cent.

 

[Packard]

And interesting story about UV cured paints used in industrial settings.

I used to work for a company that manufactured wire handles with a plastic grip that we sold to 5-gallon pail manufacturers.

5-gallon pails are listed as “shipping containers” and do not require any outer packaging for UPS, FEDEX, etc. shipments. They only require a label.

For that reason, the pail maker would print the manufacturers’ design directly on the pails, usually with silk screen printing.

This all worked fine with the infrared cured inks that were in use at the time. But when they switched to UV cured inks. The plastic grip of the handle would cast a shadow on the printed design and the smooth design of the grip would slide side to side as the pail made its way down the conveyor line, the smooth grip would smudge the ink—a huge problem for the pail makers that were now committed to the UV inks.

Luckily, our company was getting ready to have a 48 cavity mold made to produce the existing designed grips. I attended the meeting with the injection molder. While i was there, I made a sketch of a new design for the grip—one with a ridge in the center of the grip that was sharply drawn. The idea was that the ridge would resist sliding side to side, and would make a smaller mark if it did.

The injection molding engineer took one look at the sketch and said, “Forget about the old design. We’re going to tool up for this new design”.

Quite incidental to my goal, the new design was vastly easier to tool up, to run and ended up costing about 1/2 the cost for the parts. We called it a “no-mark” grip and it dominated the market. We never applied for a patent, so eventually everyone copied it.

As an aside, if you ever see an ad that says, “Printed with UV ink”, they are almost always talking about UV cured inks, and may or may not be UV resistant. Of course, they want you to think that the ink is UV resistant, but they can always claim that the ad was accurate.

 

[woodferret]

Circled in red is the 40LED (8 x 5 array) 800W light I bought from Aliexpress, and couldn't be happier with the results and price. I'll probably buy the cheaper still but longer 10 x 4 LED array one as well for a spare.

To put out 73mW/cm2 at just under 2 feet height is pretty impressive.

Thanks for the measurements. I happened to have ordered the same LED unit before seeing these Osmo UV threads here. Still waiting for my cans from Blackforest and LED from Ali. The Ali seller did suggest the 800W despite having a smaller scan - I can better understand why now. Thanks.

 

[hdv]

but Suman did actually measure it in his video at around 105mW/cm2

I'll be... I had completely forgotten. I did see his video when he published it, but failed to remember that part.

Thanks for all the good information! Like I said: really useful.

 

[luvmytoolz]

Thanks for the measurements. I happened to have ordered the same LED unit before seeing these Osmo UV threads here. Still waiting for my cans from Blackforest and LED from Ali. The Ali seller did suggest the 800W despite having a smaller scan - I can better understand why now. Thanks.

I think you'll be very happy with it. Considering the 50W cordless UV light is $1K and the larger 500W unit is $4K here, these units are extremely cost effective and very powerful.

After using mine however, I'm going to do a handle upgrade as the small handle and switch is a bit ordinary.

I'm going to replace the handle with a curved bar, and fit a momentary contact switch on it, so waving it over the resin is more natural, and the switch control will be better and more efficient.

 

[woodferret]

Retrofitting the handle was also a consideration here before I purchased it. I'm tempted actually to just put it on my router sled, as I got it mostly for cabinetry & panel work.