Denny mentioned Epoxies long shelf life. My current bench top epoxy is a circa 20 year old pair of white 2-tons I found in a long forgotten box. Other than the white component weeping a bit from separation, it performs as well as it did 20 years ago when I first opened it.
When faced with the apparent loss of White 2-ton I embarked on a search for adequate substitutes. Both the Devcon and Ace clear Epoxys were near useless for my needs. None of the clear Epoxys I tested satisfied me. Ace Hardware White 2-ton seemed to be the
same as Devcon's, though it came in smaller tubes making it more expensive per use.
Now that my search is over, as I have at least two satisfactory Epoxies to work with. Like Tom Madden said at his resin casting Cocoa Beach clinic, when you find a good product the need to search for a replacement is not necessary.
I have had excellent results with the 4 Epoxies of:
1) Devcon White 2-Ton *
2) Ace Hardware White 2-Ton
3) Ace Hardware Marine waterproof epoxy
4) J-B Weld Epoxy
*I have not found this product for some time.
No other epoxies I eperimented with were even close to acceptable. I have not tested anywhere near all available epoxies. I bought a larger Ace package of Clear slow setting epoxy and it was totally useless for my purposes. I couldn't even get good results as back filling castings for depth and support--Stay away from this stuff!
All of the above recommended epoxies are of a 50/50 mix. Back when these were available in tubes (J-B Weld still is), I would open the tubes
with an awl. I was careful to make the punctured holes as close to identical in diameter as possible. The thicker component is usually the epoxy, the thinner component is the hardener. I always squeeze the epoxy component first, in a straight line. I follow with the hardener tube alongside the the 1st strip. Squeeze out an equal length. the hardener strip will flow out making it harder to match volumes if squeezed first. Another tip; The best results are achieved when the mix-ratio favors the epoxy component, sort of 53/47. You end up with some hardener left after your epoxy tube is used up. This ratio isn't too critical, just NEVER use more hardener than epoxy as you will get flexible poor castings.
I have been a fan of the White 2-Ton Epoxy for decades, and some folks have asked me why is it better than other, more common hobby glues. For me, I rarely use epoxy as a glue. I do filling, castings, and plugging holes with epoxy, and I would lose a great working material if all of the good Epoxies were to disappear.
When the HO Stewart/Kato EMD F3A was released, it had a bizzare coupler opening in the front pilot. The real pilots have a backwards 'D' shape opening which is very apparent. The Stewart coupler mount pad also extended out from this grotesque aperture. I have seen others who addressed this problem by the traditional method of glueing in styrene followed by many coats of squadron surface putty. Depending on the time and skills invested, a good result can be achieved. I simply carved off the offending
protrusion followed by carefully stretching a piece of Scotch Tape around the curved pilot. The tape was trimmed to just fit in the curved area and not into the upper part below the anticlimber. Next some White 2-Ton was mixed and applied to the backside of the tape from inside the pilot through the opening which I intended to fill. With a toothpick applying the epoxy, I could fill into all corners and with the transparency of the tape, I was able to easily see if there were any voids. Allowing an overnight cure, I pulled the tape off and had a smooth paint-ready surface (except I now needed to carve the correct backwards 'D' opening). I can not think of any other technique which so easily can be used to plug holes this quickly and with stellar results.