Most petroleum based substances in liquid form will harden and eventually destroy natural rubber. The higher the temperature, the faster this will happen.
Since natural rubber is expensive it hasn't been used to make O rings in years. The stuff used for O rings these days is invariably synthetic and is much less likely to be attacked by lubricants - it is normally a butadiene-styrene copolymer or some sort of carefully controlled molecular weight silicone polymer. This will not be damaged by any lubricant that I know of.
If a light needs cleaning of factory lubricant and general mess, WD40 works well to dissolve and shift it. However, WD40 is not really a lubricant so it needs to be wiped off. I prefer to use heavier lubricants as they don't end up on my clothes as oils tend to. Others may have better technique than I do...
Most safety sheets are scarier than the substances concerned. The light aliphatic hydrocarbons (butane, pentane, hexane, heptane, octane, etc.) have essentially no chemistry, they react with oxygen when provoked (i.e., they burn when you light them) and that is about it.
The light stuff is being used as a solvent for some heavy petroleum goo which has been hydrogenated probably to make it less chemically reactive - this will also make it less toxic as it should get rid of most aromatic (ring-shaped, like benzene which is very nasty stuff) substances in it. However, it is designed to coat, not to lubricate, it tends to wash out other lubricants. I use it as a solvent rather than a lubricant and wipe it off afterwards. This may leave a small amount of heavier oil around but I try to get rid of all of it by cleaning thoroughly. It does tend to get everywhere though. This is what it is designed to do.
The smell when it burns is quite distinctive and doesn't smell like any hydrocarbon I'm aware of. However I am not current in chemistry, it is 28 years since I graduated and I don't work in the field any more.
What I can gather is that silicone oil is not good on silicone ring, and petroleum is not good with others like EPDM. Prolly all because of the solvent issue. Nitrile seems resistent to everything. So basically, we're screwed unless the chinese manufacturers let us know what they use.
Here's a thread that I read a while back that helped with my lube questions. Most people here already know about it and maybe you already read it but here it is anyway.
Nitrile is stated to be the cheapest. Unless there is some very good reason, I'd not expect them to use anything else. Ozone and weather resistance aren't very important inside a light though the heat resistance might be. I suspect that this isn't melting of the ring, but hardening and cracking.
Found some bulk prices. Nitrile is about $3000 per ton, natural rubber is currently around $3800 per ton. The price difference isn't as big as I thought.
I myself still need something. My fake Solarforce L2 arrived dry and is still dry nearly a month later. Only had aerosols, motor oil of some kind and chain lube (which I found out had hydrocarbons), none seemed a great idea. Had a look at a local hardware store and didn't find anything better. The CPF thread was interesting but as with most things CPF fairly US centric.
Have now found silicone grease http://newzealand.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0283404 about NZ$12.50 including GST (and delivery is free) for a 50g tube which isn't too bad. May have a look again in the plumbing section of my hardware store to see if there's anything there although I'm not hopeful.
I was wondering how likely it was that the o-rings would actually be damaged, may just try Vaseline. Or the chain lube
I've used chain lube in the past. The stuff sold in sprays for chainsaws works well but is a pig to remove from the places you don't want it to go. It is probably a bit too tarry for small stuff though.
The RS silicone will do fine, it likely came out of the same factory as the stuff I use.
I've not had O rings eaten by any lube I've used though plenty of rubbish quality ones have fallen apart on me.
Couldn't find any english link for this product, but here is the link with Google translator: http://translate.google.pt/translate?js=y&prev=_t&hl=pt-PT&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.wd40.es%2Fdynamic-GRASA%2520COMPACTA.htm%3Ffid%3D4%26cid%3D9%26pid%3D1061&sl=es&tl=en
Ummm I am not using that brand, but in the package says "grasa de litio", so I imagine that is the same product but with another brand/manufacturer. The color of the grease is something gold, brownish, yellowish.....
Well, while it does the job, I dont recommend to use lithium grease in expensive flashlights or flashlights that you love, because, as I said, although it does the job, there are better products specially designed to do this.
For example I will NEVER apply lithium grease in the itp A3, because it is too gross for that tiny threads, and the flashlight is expensive (quality), so better for use it on cheapo flashlights
In spanish there is a phrase that says "lo barato sale caro". Cheap things will be expensive in the future, is hard to translate.....
If money is not your problem use super-lube, nanogel, or something about 5-10 dollars. Something specially designed to that purpose
It's kind of a transparent/yellowish grease, not thick(gross?) at all. Here it costs 2,25€ for 150g, and I only have to walk 50m to get it. Saw it on a local hardware store.
Think I'll give it a go. I don't normally lube the lights. Just use them as they come.
Not being able to speak or read any language other than my own (And I am only marginally literate in my own langauge) and English (And a lot of people think Scots and English are the same language. They are wrong.) I can't comment on the Spanish stuff. I can just about buy a bus ticket or cigarettes in Spanish but that's it.
However, I do usually clean lights on arrival to remove metal swarf and the like. Since I don't enjoy the squeaking of dry metal sliding against dry metal I usually put in some lubricant to shut them up. I've used many things including heatsink goo - which is a very, very bad idea as it contains a lot of metal oxides - AKA cutting paste.
I was wondering how likely it was that the o-rings would actually be damaged,
Unless you have a special attachment to those particular rings, you can buy replacements for next to nothing at any hardware store.
The mineral oil/ baby oil I describe above is incredibly easy to apply (put some in a small squeeze bottle) and very clean (odorless/colorless/great texture). 1 drop on a thread will usually be enough. It also works superbly on any metal tools you may have.
The goo-ish thick and messy lubes I'd rather not use at all and leave it dry.
I recently purchased a Seraph wich had a lube that I thought it was quite nice. Ultra silent, and quite thick and silverish.
Tried to take it out with a tooth pick, just to feel it. It was kind of thick and gooey. Asked the seller, and it was Nyogel 760g.
Just wanted to try some lube. As I said, will give it a try. Monday, or Tuesday.
The non english words: "lo baratosale caro"(spanish) and "o baratosai caro"(portuguese), mean: " the cheapwill cost you a lot". Or something like that.
The silicone grase used for oring lube is DIELECTRIC (not conducts electricity).... so.... if we put it in a flashlight with not-anodised threads (which uses the threads to conduct electricity) it will stop working?
Well, "dielectric" has a very specific physics meaning, but for our purposes here the grease is an insulator.
It doesn't matter on the threads because the mechanical pressure of the locking threads easily displaces the liquid. If anything, the liquid can help suspend and displace other particulates that otherwise impede conduction.
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Actually if the grease you use is the thick and not flowing type, it might impede conductivity. But if your light has tight threads (you feel some resistence when screwing it w/o the o-ring), it really shouldn't be a problem.