A Perfect Dedome?

As I’m still very green at dedoming, I really don’t know what the actual cause is. The ones I’ve tried it on are XM-L2 U2 1a. But I’m not really sure if they had a hint of green in them in the first place.

Thank you djozz for saying that. You are right. I don’t know the exact bin of my first few. Knowing, what I have done since, I am much happier with the outcome. Still, even though I’m color challenged, I see a pretty big difference between a domed, and de-domed led. Everyone says they get warmer. I don’t know what that means. All I see is blue, green, yellow, orange , and red :slight_smile: .

That’s what I’m thinking. Dunno anything that’d eat certain “types”(??) of phosphor, eg, those that emit red and yellow (leaving green), yet leave alone other “types”.

Unless different phosphors are put down in layers vs as a mix, and a sloppy dedome takes off a bit of the topmost layer. But you’d see that on the blob of silicone that comes off, I’d imagine.

Don’t think phosphor would oxidise, form a hydrate, etc. Especially if nobody notices any green-shift of a long-dedomed LED that’s been in a flashlight for years.

Ha!

Some of the LED’s I have de-domed had a bit of green on the very low modes. I have been experimenting with heating up the LED after the de-doming this actually seems to reduce the green significantly. I don’t have any specific method yet it’s more trial and error at the moment. I heat the LED on the MCPCB as you would with a re-flow, I find this eliminates most of the green on the low modes, so far I have done four (two XM-L2 & two SST-40) and they turned out great. I still need to do some more LED’s to see if I can replicate the results or if I just got lucky.

Most of the LED’s I have de-domed until now was of unknown tint but the difference between a C or a D tint must have a impact on the de-domed tint. One of the best tints so far was a XM-L2 3D came out really nice if you like the warmer tints.

EDIT :

I have ordered some XM-L2 U3 0D and 0C to see what difference if any the tint makes.

Here are some measurements on the tint shift from dedoming: de-doming: illustrations for color changes and increased luminance

I think the majority of the tint shift is a result of the dedoming itself rather than the method. See here for some discussion: Flashlight Optics - Dome, Dedoming and Throw

I’ve read through this before and I’m bound to agree with it. But then I read that Mitko and another member here mix chemicals so that no tint shift occurs. Then again it’s impossible to know if it’s true or not when they are reluctant to share their method…

In all fairness, mitko did share his meathod here,

Ah, I forgot about that post. But he never revealed how much he used of each chemical.

It seems that people with the best results are using a mixture of chemicals. I’ve wondered, are the domes pure silicone? Also, I’ve wondered if there might be some kind of glue or other substance to help the silicone adhere to the substrate. I would think silicone would adhere on its own but after dedoming a number of times the silicone seems different where it meets the substrate. I believe that it is just silicone but i through these thoughts out there in case I’m wrong.

How much did you heat the mcpcb? Just enough to melt the solder under the LED or longer than that? And did you use a hot plate or iron?

I got these bottles, hit them with a hammer, and they all break.

This new batch of bottles, I rinse with bleach before hitting them, and most of them stay intact.

That’s kinda the problem, that there’s no redoing the dedome with the same LED. Someone gets an “old” batch of XP-Gs, then a “new” batch of XP-Gs, and claims or actually sees a difference with a different solvent, but there’s no way to know that the LEDs all had the same exact tint (they’re tint bins, don’t forget) beforehand, and then acted differently after dedoming.

Or as I asked afterward, wotnahell are those chemicals. Spelling counts in chemistry, else things go boom.

I did a new XM-L2 dedome with my ‘nitro-verdünner’, but now left it overnight without heating up (it is summer here so +20 degC even at night). The dome was next to the led the next morning. After drying I just blew the last bits off.

I guess that you have a good point there, Lightbringer.

How is the tint Djozz?

Did any of you ever asked any led manufacturer about this?

Maybe we should ask them to include a “recommended household/industrial list of chemicals to use in hot* bath dome dissolving procedures for high intensity applications”, with notes and remarks, in their datasheets.

That could be one of the problems of trying to figure out if how you de-dome matters.

However, consider this. A while back I bought a hundred XP-G2’s from the same supplier of the same bin. I de-domed around 90 of them successfully using the same method and each and every one of them had the same tint once de-domed. I remember them in particular because they came out with a rosy tint after de-doming them and I loved it. I think there is a lot more consistency than you think when it comes to bins, so that it should be possible to find out if different chemicals change the tint or not. Wouldn’t you say that If I had de-domed half of this batch with Gas and got rosy tints and half with nitro and got green that it would in fact be the nitro that is the culprit? Also considering that dozens and dozens of members here have all reported back on their results and have agreed that some Bins are nice after de-doming and others are not, wouldn’t this also suggest that Bins are fairly standard? Different people around the country get the same results from the same bins so that certainly makes it seem that the bins are fairly consistent to me.

Here's a list I found in random google search. They seem to be ordered in terms of effectiveness..

Ooh, what bin?

Absolutely. That’s why we need the Scientific Method™.

If someone is going to dedome 100 LEDs, all from the same lot, maybe split them 50/50, gas one and nitro the other. Or whatever solvents you’d use. First spot-check the LEDs before dedoming to see if they hold up as far as being close in CT and tint.

Then compare the results. If one solvent gives a nice color and the other gives a horrid green tint, then we absolutely know that the solvent makes a difference.

But some get their LEDs from FT, others from KD, others from MTN, etc.

And an LED could be on the ansi-white chart on the rightmost edge of a 3A, and another on the leftmost edge of a 3D, yet look almost identical, despite different labels of “3A” vs “3D”.

Similarly, a bunch of 1Ds might be alllll over that patch that qualifies a 1D, one close to 1A, the other close to 2A, an other greener one close to a 1C. That’s what I mean about a range of CT/tint within a particular bin.

Good find, Jared! :+1: