Is it safe to carry a filled glass carboy by its neck, using one of these carboy handles?
The weight of the glass + beer, combined with the brittleness of glass, makes me nervous (compared to a PET carboy, which is a more elastic material). Is it possible for the neck of the carboy to fail this way?
Do not carry a full carboy only by the neck. All of that weight is concentrated in the small area of that carrier, exerting a lot more force than the neck was designed for. It may not happen often, but the risk isn't worth the reward, in my opinion, especially when there are much better options to moving full carboys.
Some folks like to use milk crates.
I always use a Brew Hauler when moving carboys. It's safe and much easier to lift and move around than the handle. I even use them on my plastic Better Bottles, just because they're easier to handle that way, especially when you have to lower them into a chest freezer.
I use the handle as a steadying tool and something solid to hold on to when it's slick from water and cleaner. I support the weight of the carboy from the bottom with my other hand while holding onto the handle.
I really wouldn't recommend carrying a carboy simply by a handle on the neck unless it's totally empty, and maybe not even then.
Yes, it is possible for the neck to fail if you're carrying a full one by the neck with a handle.
I came across this just today: http://www.homebrewtalk.com/f19/carboy-vs-thumb-334851/
I've seen more than one story like this.
I will never carry a full carboy by a handle on the neck; milk crates or straps.
