no reason to use the bathtub. Go to Target and buy the largest salad bowl they have. There are also some tubs in the storage department that would probably work as well. I never soaked my frames BITD, got the flux off mechanically. Most decent fluxes will come right off with a wire brush.

hah, I wouldn't use the tub. I am using an old mixing bowl I just found. Size looks compatible to your ice cube and fits all pieces fine. I can get most flux off with a wire brush on an angle grinder but some of the more glassy residue needs a bit more work.

After spending over 20 years as a union welder, underwater and topside, there are certain issues of welding that are always considered and determine the strength of the joint. When done properly, the welded joint should be stronger than the pipe itself (tubing).
1. The parts should be grinded down and as clean as possible.
2. the fit of the joints should be uniform all the way around. The gap in between the pieces should also be uniform. The size of the gap should allow enough penetration to fully breakdown the 2 pieces being joined together to produce a 100% sound welded joint,
3. Heat, Heat can fix and cause problems in the joint to be welded. In the hands of a good welder, all joints can be welded and xrayed for a passing grade. In the wrong hands you will have a boogered up mess with limited penetration or to much penetration and a boogered up mess on the inside and outside
4.Aluminum or steel, TIG welding is the best and there is no close second place techniques. Nuclear plants always have at least the first 3 passes TIG welded. And there is a reason for this, QUALITY, CLEAN welds period.
5. Technique is so important for tig welding. In the right hands you will have a weld that is indestructable and also look great. Should look like a bunch of dimes layed out. no gaps inbetwen and no spots were they build up. If you can look at the weld when it is completed and see crust stuff towards the outside of the edge, equals to hot and or moving to slow. If you see a weld that looks like what we call "Bubble gum welds", which looks like you could snag your shirt on it while walking past it, that is also a no go
Good welders dont have to take their grinder to dress up their last filler pass (Cap). If you see this it is time to ask questions to your welder.
Anybody can put two pieces together. how many people can weld this stuff,or any round tubing or pipe together and then get it X-rayed for a passing grade? If I was building a frame there wold be zero braze on tools around. everything will b tig welded.

Hope that helps Ifyou have any questions or comments please state them.
D
Ride safe