Hmm, fun fun
Reasoning for my intitial questions:
The type of plate you are gluing to is important, there are certain brands of (esp cast) acrylic that simply do not glue well, not matter which method you use. Polycast, Cyro (extruded or cast), PlexiGlas (extruded or cast), and all of the extruded materials all glue well so if you stick with the top 3 names, the material is not a major factor in your bubble problem IMO. Some of the cheaper import brands come from factories in which resins are bought on the world resin commodity market without regard to consistency of quality and the quality control at these factories can make the use of cast specious at best. Ie, even though we want to use cast acrylic, if we are using *bad* cast acrylic (for our purposes), you still won't achieve the desired results as the material is pretty much incapable of allowing for those results.
After material choice, preparation of the tube ends is the next most imortant thing IMO. Bad cuts in the tube ends will cause inferior joints in most applications. The tube should sit flat and without gaps. This is an easy thing to take care of for small diameter tube (<8" dia). Just tape a pice of 220 grit sandpaper down to a flat surface and grind the ends on the sandpaper in one direction. If you try to grind it in both directions, most folks have a tendency to rock the piece a little, causing an uneven surface.
Cast or extruded react a little differently, extruded tube reacts much faster and soak time should be minimized to reduce risk of crazing. If proper edge prep was used on the tube, soak time for extruded tube should be no longer than it takes to apply the solvent. With cast tube, maybe wait 15 seconds or so provided the tube ends were prepped well. Waiting too long in either case causes the joint to start to set prior to pulling the wires and then you're just fighting the joint.
* The times mentioned above are based on my experience, YMMV.
The dipping method is something that I would rarely recommend but can be workable. Basically, you're filling a poly tub about 1/8" full of solvent (water thin) and soaking the tube ends in the tub, then placing the tube wherever you want it. It's sloppy, slow, and wasteful. I don't know of any mfr that uses this method.
I would agree that applying 16 after a solvent joint has dried does further stress the material and can induce crazing, esp in extruded materials. I know many DIYers (and some mfrs) do it, but should be avoided if possible.
16 can work by capillary method but requires a large gap and is sloppy. Capillary actioin is simply surface tension wick a solvent into the joint, since 16 is still somewhat liquid - it will follow the surface tension. It still requires at least a decent sawcut edge and since it only takes a minute to prep a decent sawcut - why bother IMO
I would argue with the idea that joint strength using 16 or equivalent would be any higher than that of solvent. After all, 16 is just solvetn with MMA/PMMA in suspension. They work by the exact same action, solvent breaking down acrylic. I just don't seee, even in theory, how this is could be derived.
Henry, It does appear that the S2000E is similar to WO 3 or 4, S2002 (S2000 with some gap fill) is similar to WO 16 but without an MSDS, kinda tough to find out how similar these are but if you read the tensile strength notes on both - you will find the results to be exactly the same.
The tensile strength for SPC doesn't mean much IMO without knowing what it is made from, it could simply be acetone or MEK which of course yield a lower bond strength. Please compare S2000E to S2002 (S2000 with some gap fill) as an apples to apples comparison.
Tensile strength of joints are theoretical at best though for our puproses as we will never put that much stress on a joint in operating conditions. Doesn't matter if theoretical tensile strength of a joint is 2500psi, 8000psi, or 25000psi, we will never put that much direct stress on the joint in operation. Furthermore, if it doesn't get a full joint or bite into the acrylic - these numbers are absolutely meaningless.
HTH,
James
