I've given up on super-glue or tape in joining my top and bottom 32 Oz. clear plastic cups. The tape often comes off, as does the super glue when I try to pick them up by the lid. With this new method, I now use a standard soldering gun with a pointed tip to join the two lids. It takes about 1 minute to join the cups going slowly and carefully 'but I was doing it in half that time' normally, and it hardens almost immediately.  You can see in the top picture #1 pic. that I'm holding my soldered cups mid-air and even when I tried shaking them apart, they held fine even with the weight of damp soil. You can make a continuous line #2 pic. or punch through the side in four places #3 pic. (which leaves air gaps along edge, but it still holds o.K.) I prefer doing a continuous hot joint. (Note: Update- after experimentation I found that even a very small hot joint 1/16 of an inch in 4 places works very adequately and is much easier to remove with a razor blade.)   I also experimented making my bottom cups into an air-pruning mini-pots by punching in tiny holes with the hot soldering iron. #4 pic.    Note: As an experiment, I tried joining thin plastic water bottles but it didn't work well as it was hard to line up the two cut edges and there was not enough plastic to melt together where the edges met. The heavier clear plastic bottles should do fine though.)    Hope this helps those of you who are tired of taping cups together.





    





   

Nice. Do you cut them open or break them apart when you prepare to up-pot?

This seems too labor intensive for me.  I don't know what kind of tape you're using, but any simple clear tape holds just fine.  Maybe try not picking them up by the dome as often or at all.  I get plenty of humidity even with the basic setup.

I use blue painters tape to hold the cups together. I can even take it off and put it back on. The tape is designed for protecting the trim while painting. It works very well for me in this application

I tried the 2 cup method and had high hopes for it.  But, I could NOT keep the white mold at bay.  Grew on the medium, grew on the cuttings.  Tried sterilizing with dilute Clorox or H2O2.  Even tried nuking the medium.  Back to Parafilm type grafting tape.  No, the medium was barely (almost imperceptibly) damp.  I don't know what I did ( or didn't do) that was different than those who had success.

My only suggestion is that you consider your ventilation carefully. The fumes that come off of polypropylene and other plastics can be quite toxic. 

Sorry about your trouble with mold 'SR Bill'-it may have something to do with your environment or where the cuttings came from- We all deal with mold but yours sounds aggressive.   Too answer a comment, it wasn't too labor intensive. 30 seconds +. I was using blue painters tape as well, but I do move my cups about often as I don't have a permanent place in the house, so the added security of being able to lift it by the dome, with zero qualms, works. This is a new method for me. I haven't taken any apart yet but am sure a razor blade along the edge will suffice. As far as fumes go, I have a fan  going. Everyone has a method that works best for them but if you hate messing with tape or glue I think you'll be pleased that you gave it a try.

That sounds like a cool idea, Noel. I think I'll give it a try. Thanks, Bill

I use scotch tape only because its simple.
Of course you learn quickly to pick it up with the bottom cup.
:)

Doug