So why does an LED get warmer when it's De-Domed?

I’ve read the threads on the breakthrough of using gasoline/petrol (or even other things such as Coleman fuel, diesel, and acetone) to greatly ease de-doming.

I think what surprised most or all of us, is at least Cree LEDs de-domed in this manner, became WARMER in tint, not cooler. And not just a little warmer (texaspyro was seeing a drop of around 2000 Kelvin; see XML and XML2 de-dome color temperature changes ).

What I haven’t seen (or I missed) is a reliable explanation as to WHY this is happening.

In the past, de-doming seemingly typically involved damaging/removing some of the phosphor. Phosphor changes the LED’s innately ultraviolet or violet light, to the visible spectrum.

My guess (and only a guess) is de-doming via gasoline is so effective at leaving he phosphor intact, we’re seeing that perhaps the dome itself kind of ‘re-cools’ the light after the phosphor does its job? But that seems incredible, seeing as how clear (and small) those little drops of silicone are. And considering how difficult full-spectrum white, especially warm white LEDs have been to develop, I doubt Cree would then add a substance to the LED which made it significantly cooler.

My previous understanding was that to make the LED warmer, more phosphor would need to be added. But that’s obviously not happening here.

The irony is that a lot of older low-end, overly cool LEDs in our collection could potentially end up getting an actually really nice neutral-ish or warm-ish tint (if you like that kind of thing), which people used to pay extra for.

So has it been determined why this is happening? And is this phenomenon restricted to Cree?

(As a caution, just in case anyone missed the gasoline breakthrough, good results seem reported with most modern Cree models, but not XR-E and MT-G2, for different reasons.)

Dr.Jones posted an explanation about why this phenomenon occurs. (I was quite surprised by the user name resemblance.)

Sorry I’m on my phone but long story short, the dome prevents light from going back into the phosphor.

Nope, no relation, LOL. His writings are great, but not for the common man. Despite being in awe of his knowledge, I usually feel like I need an interpreter when I read his stuff (having nothing to do with the fact he lives in Germany). I guess he’s a Ph.D…

Apparently some people here actually follow much or all of what he writes, but I think most are not honest about not understanding it. I have no trouble admitting I struggle to follow him at best, and I’m no academic slouch. He’s one of the few usernames I remember from CPF years ago, before BLF. I almost wonder what he’s doing here, lol. He was always respectful back to the CPF days, so I saw him as one of the ‘good guys’ there, still do of course.

I read a long thread where he mentioned something like that, but I didn’t totally get it, and it was buried in other details I was attempting to follow. Thanks for the translation :slight_smile: .

Anyway, that confirmation surprises me that Cree knowing applied a treatment to their LEDs which made them usually overly cool, at a time when that was a major weakness of their product, even leading to frustrated terms like “tint lottery”. Few in those days complained of their Cree LED being too warm. And a lot of those Cree LEDs went to low-end zoomies (remember the “x2000”? lol), whose lens enhanced the coolness even further. Not sure if that lens coolness is the same as “purple fringing” in photography, but it seems maybe similar.