Tritium and Epoxy

[cdosrun]

Hi,

I know the issue of epoxy for tritium has come up a few times, and I have read all the references I have found but if someone could provide some advice on these specific questions, I would appreciate it.

So far, with tritium, I have just used cyanoacrylate adhesives with them, obviously they stick, but they can't really be used to protect/pot the phial; I've only had one break so far but I would like to pot the new ones properly when they arrive. I am sticking them in the tail recesses in a few Fenix lights so there isn't a proper cavity for them but they are quite well protected by the light.

I am toying between two different epoxies (will probably get both types to fulfill the minimum order requirements) and how to use them best. One is a slower cure type http://www.intertronics.co.uk/products/opt5012.htm and the other is a faster cure http://www.intertronics.co.uk/products/opt5013.htm

Firstly, is the 3% shrinkage with the faster cure type going to put too much stress on the Tritium phials (Bart's ones)? Secondly, will the phials stand up to sitting in the oven, in the epoxy, for 90mins at 80° (slower epoxy) without damage?

The advantage I can see with the slower one is it has a very low viscosity and a long working time. So if I wanted to put two pieces in on opposite sides, I could place one in the oven on one side to dry, and then repeat on the other side; there would be less wastage of epoxy.

If anyone has a better epoxy to suggest (that I can buy in the UK) I would appreciate it.

Thank you,

Andrew

 

[Stillphoto]

I haven't potted any trit with it yet, but here in the states there is a Devcon brand of epoxy that is glass-smooth and has around a 30 minute cure time, no oven needed. It has provided me with very professional looking results with glow powder and other things I've played with here or there. The nicest part is that it gives you enough working time (probably around 5-maybe 10 minutes) before it gets harder to work with.

Of course you can use what Don (McGizmo) uses on all of his lights, which is Norland brand optical adhesive. Seach cpf and you'll get more info on which one he uses.

Best of luck!

 

[Mr_Light]

I used 5-minute Devcon Epoxy to attach Bart Vials to the tail of a P1D-CE. Worked great for me.

 

[cdosrun]

Thank you, that's really helpful. Looking at the specs for that stuff, it is quite similar to the quicker curing of the two epoxies I was looking it. That's the way to go then, and allow it to cure at room temperature.

Andrew

 

[DM51]

AC says he's using Devcon-5 for his glow-fobs (GITD and tritium types) - see post #70 in this_thread.

 

[lukus]

Don't have any Fenix's, but if the recess you're putting it in is a gap in the threaded cap you'll glue it shut. The description has them both with very low viscosity, so you'll have difficulty keeping it from going where it shouldn't.

Generally speaking of epoxies, the faster setting ones are less waterproof. I notice that waterproofness is not mentioned in the fast setting stuff you linked. I had something I had used the five minute stuff on that would get gummy and nasty after a full day in a sweaty pocket. Of the two I would go with the slow set. The little premeasured bags are a really cool easy way to do the mixing. On the downside is probably price. That stuff just looks expensive, and you only need a very small amount each time.

I recently bought a gallon and a half of very clear long setting epoxy off of ebay. Just a bit over $100 U.S. shipped (to U.S.). I needed a bunch because I'm messing around with making some high pressure laminates. Anyway, the stuff is very clear, doesn't bleed colors like some epoxies, non blushing, non yellowing. Some of the best stuff I've messed with, and it easily polishes. I would try ebay for some alternatives. Smaller quantities are harder to find, but, depending on the price of the stuff you linked, might not be a big deal.

 

[Rudi]

Clear nail polish works too. It shrinks as the solvent evaporates, and you can keep adding a bit more until you have the desired thickness. If you change your mind, you can remove it after softening with nail polish remover (acetone).

 

[McGizmo]

Fast cure epoxies are fast to cure to the touch but the actual large molecular linking of truly cured epoxy can take up to a week as with the slower curing epoxies. People who develop sensitivity to epoxies will have problems sanding epoxy after a couple days because the dust is really not cured and inert yet.

If you are after a good strength and a good bond, the slower cure epoxies are a better way to go. Post curing epoxies almost always shortens the cure time and can give you "hard to the touch" and handleability quicker that waiting for room temp cure. Post curing epoxy also typically elevates the HDT of the epoxy which means that it will take a higher temperature to soften and weaken the bond.

Many epoxies have an amine blush if they cure in the presence of humidity. This amine blush which feels like oil on the surface is water soluable and easily removed with soap and water. If you are building up a lamination, this blush must be removed to insure inner laminate bonding and strength.

Most of the comments above have little bearing on mounting and potting H3 vials as bond and material strength is of little consequence!! One consideration of the fast cure epoxies here though is that of bubbles. Many of the fast cure epoxies have bubbles form and these bubbles don't have the chance to escape.

 

[cdosrun]

Wow, thank you for all the information this is really useful. The epoxies I linked are not cheap and there is a minimum order of £30 (about $60USD). I have had a look on eBay but the epoxies I have seen have to be shipped to the UK anyway.

The places I was going to put the H3 in were the recess at the rear of the AAA Fenices (obviously masked to prevent the epoxy encroaching onto the split ring area) and in the switch recess of the tail switched Fenices.

Having seen Newbie's post on epoxies I was contemplating curing them in the oven to raise the Tg so as long as the H3 isn't damaged by the pressure increase, that is probably the way to go; the slower cure epoxy would harden reasonably quickly like that.

This looks like it is going to get expensive, so I will probably buy glow power to chuck into some epoxy as well for even more effect.

I honestly didn't think I would spend this long deliberating over the comparative benefits of epoxies. Oh well, it is a strange hobby.

Andrew

 

[souptree]

Oh well, it is a strange hobby.

Last night I had the following conversation:

Me: Check this out! This is the brightest glow powder in the world infused in epoxy! :naughty: :twothumbs

Her: You sure have a strange hobby. :thinking: :shakehead

Me: Yeah. Well, OK, I have to go and hit reload now and see if the Mules have shown up.... :candle: