super waterproofing. liquid gasket type sealant for flashlights?

What I wonder is if there's a temporary sealant that works like an adhesive but breaks cleanly free when twisted. The sealant would basically go in the little space between the very bottom(inside end) of the tailcap and the body of the light, or the base of the head and the body of the light. It would cleanly seal the tailcap/head to the body and stop water before it even reaches the o-rings, which are located further up. The sealant would be applied after the head and tail were already secured and not going to be moved. I do not mean sealing or applying anything to the threads. Obviously this would only be good for clicky lights which don't require the head or tail to turn for adjustments and the sealant would have to be reapplied each time the head or tail was removed. I think it would be worth it if one could trust the sealant to break relatively cleanly and without too much torque.

I hope my description makes it clear. It may be difficult to picture. Really any ideas on super-waterproofing that are additional to o-rings, rather than relying on them is of interest to me. I'm not aware of anything like this and I wonder if anyone has tried this or has a product to suggest for me to experiment with.

This may be stupid and generally not necessary but I keep thinking about it. It is admittedly not a critical design modification but I know most of us understand overdoing things for fun, not neccesity. Not many people really need the twenty flashlights most of us seem to have, afterall.

Plumber silicone? Not pretty, but effective. You may need rubber strap wrenches, but it adheres lightly enough that you probably won't need channel locks. I don't know what this will do to silicone O-rings.Lubricated O-rings keep most machinery in the world sealed against high pressures. Engine pistons, water pumps, and hydraulics all work fine with thousands of PSI and remain sealed for thousands of cycles. Dry or damaged o-rings fail, as on Challenger. Keep them lubricated and cleaned.

Plumbers putty perhaps. It's basically a clay-like substance, really cheap and often used for sink and drain installations, it's somewhat thixitropic, very soft when you mold it with your hands and then firms up once you've molded it in place, but never actually "hardens". Not to be confused with pipe dope or repair putty which is usually epoxy based and extremely permanent. The only place this would be handy is in a non-rotating joint, like say a head or click swtch that for whatever reason can't have an oring fitted.

How about teflon tape on the threads.

thanks for the ideas guys. I do really have alot of trust for the o-rings since they've never failed me before but I just love the idea of water never even reaching them. That's why teflon tape, which is a good idea and one which i've used before, isn't as interesting to me. If the tape is keeping water out, that means the o-ring has already failed. I'm currently trying a brand of liquid gasket maker from a tube on a relatively cheap light I found on the sidewalk but now I doubt I'll be able to get it open again without vice grips. Now I'll try those other two suggestions too. I'm not familiar with them yet.

reppans said:

How about teflon tape on the threads.

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Teflon tape is intended for use on tapered pipe thread, i.e., the diameter of the thread changes over the length of the joint and the threads jam into each other as the joint is tightened. Its effectiveness on a straight thread, as used on flashlights, is doubtful.

Depending on the light, bicycle inner tube can be cut and rolled over the light like a super duty condom. Doesnt cover the lens though. Or just use a condom, tie it off, and you have a diffuser as well.

Yamabushi said:

Teflon tape is intended for use on tapered pipe thread, i.e., the diameter of the thread changes over the length of the joint and the threads jam into each other as the joint is tightened. Its effectiveness on a straight thread, as used on flashlights, is doubtful.

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And you can drag the tape over the o-ring, ruening the o-ring seal when you put the cap on. Just keep the cap + o-ring clean and lubed, and dont worry I have used lots of different non dive lights under water (when freediving) with no problems. Used my l2t under a boat today. The only thing i do is check for dust or hair on the o-ring and the cap area where the o-ring seals. And check if they are still well lubed.

condom it is then. or maybe I will just go back to trusting the already proven o-rings. for now i'm going to keep experimenting with the other suggestions and maybe nixing the thread tape

Are you planning on taking these lights diving? Or are you just looking for a way to beef them up?

Silicon. It should even be reusable, but will only act as a second o-ring and not a sealer after the first use.

You might want to think about Plasti-Dip. It's a paint that dries into a rubber coating, comes in different colors, and can be peeled off. It's available in cans for dipping (the idea is that you dip tool handles to make rubber grips) or in a spray can. Obviously, you don't want to coat the lens, but it may work for the rest of the body. You could try it on some scrap metal or something first. It needs to be pretty thick to be peel-able. I'm not sure how water proof it is, but it's worth looking in to. Most home improvement stores carry it.

I would like to be able to take most of my lights diving. I'm not currently scuba certified so I'm not reaching really serious depths but I do snorkle often and get deeper than the greatest depth any of my lights specify which is the IPX8 standard and two meters depth. I've only used my surefire g2l when snorkling and it has done well up to about twenty feet but I don't like just hoping it works without any certainty. I know it's a twisty so it wouldn't be the one I apply anything to. Thanks for more ideas guys.

I'd use hot glue, you can even remelt it

james22 said:

I would like to be able to take most of my lights diving. I'm not currently scuba certified so I'm not reaching really serious depths but I do snorkle often and get deeper than the greatest depth any of my lights specify which is the IPX8 standard and two meters depth. I've only used my surefire g2l when snorkling and it has done well up to about twenty feet but I don't like just hoping it works without any certainty. I know it's a twisty so it wouldn't be the one I apply anything to. Thanks for more ideas guys.

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One problem you will run into is the switches. The heavy pressure of the water will compress the air in the rubber boot around the switch, clicking the switch on permanently and flooding the host when the boot gets pushed far enough into the light. Atleast those were a couple of the things I have been told from some of the more active diving members here on CPF. You would be better off trying to water proof a Surefire that has a twist on action to avoid that problem.

What I've found to work best is, depending on the light but it applies to my Solarforce L2's, is that the inside of the tailcap is machined aluminum. What I do is wet sand the aluminum with progressively finer sandpaper until all the machining marks are gone. Then I polish that sanded surface to a mirror finish. This way when the o-ring seals it seals 100% airtight.

But if the surface is already anodized I wouldn't touch it. It gives a very good seal as an anodized surface. All that's needed is a decent lube and I've had lights spend a whole night at the bottom of a hot tub lighting the hot tub for the night and not a drop of water got in it.

What does it mean to flood the host? I had heard of pressure activating a clicky tailcap at significant depth but do you mean the rubber boot tends to fail under the pressure and allow water in?

Sometimes the boot can be pushed far enough into the light that the seal between the rubber boot and the switch is broken allowing water to enter the light. It's another area you have to make sure is properly sealed against that kind of pressure.

Flood the host means to allow water to enter the flashlight.

If I wanted to go diving, I'd just look into dive lights; other flashlights are not designed for diving, therefore a variety of things could happen depending on how deep you want to go.

Cataract is dead on with this, though I do understand your want to use your regular flashlights to go diving. I had the same thoughts when I got certified. I have since come to the conclusion that a properly sealed flashlight would do fine for snorkeling and the like, but not quite for full on diving. Serious dive lights sometimes even go so far as to separate the switch, the reflector/optic module, and the power source. You keep the battery tucked on your back, hold the light in your hand, and flip an actual switch on your chest to operate it.