Mick has given you the answer I will add a few things of my own, seems like Mick and I have a few things in common.
Kodak made monster RA4 roll paper , and a few labs worldwide had super size process capabilitys for RA4 processing, I believe Duggal in New York is still doing this. There has to be one in Europe as Stursky(sp) needs his prints somewhere.
I worked at Jones & Morris in 1980 and we had a 72 inch processor and used Durst 2501 horizontal enlargers to make extremely large murals.
We would even make panels that butted together would fill entire rooms.The best size negative would be 8x10 and we were able to work from original camera negative OK , otherwise the photographer would be compelled to use chrome and we would make 8x10 internegs. Kodak 6121 I believe eh Mick?
I wonder if PE designed that emulsion, I sure used a lot of it in my youth.
These super size prints Mick is describing were a daily thing, and we were very careful in the setup as he explains.
To even consider RA4 in trays is like thinking about washing down a Rhino with a toothbrush.
Today there is wide format inkjet machines and wide format Rhoe flatbed ink jet that can make super size prints but their quaility is nowhere near a RA4 optical print. YET, but with stitching Large Format Film.. oh shit here I go on the dark side again.
I will admit they are getting much better and we will once again see a resurgence of monster prints from stitched large format capture done on a flatbed.
The Durst Rhoe unit, right now has a 8 ft high by whatever length you can feed into it. therefore you could see at a gallery wall near you a single piece of imagery 96 inches by 40 ft or longer. The Durst Rhoe is basically a epson print head driven by a Lambda software.I have assess to one of these, print price 10k any takers.
Plexi and sintra come in monster rolls of hugenormous size and can be imaged directly on... I suspect one of the usual characters(Sturky,Jordan....} will figure this possibility some day and make the big one. just stitch 20 8x10 films and slowly image onto the plexi or sintra, then overlaminate with hot lam... you heard it here first folks.....I can imagine one day the commercial side of my business would consider one of these suckers, but the 1/2million plus 30k per year service contract is not for me, I put down on a Lambda and not to willing to put another monster on my shoulder again.
The widest generally available RA4 colour paper was from Kodak. It came in various sizes but the largest size I ever used, was paper that was 6' wide by 100' long.
The actual largest single one piece print I have ever done, is 6' wide by 18' long. This was around 23-24 years ago, things have changed somewhat.
The roller transport developing machine was 6'6" wide, let me tell you that feeding in a piece of paper that long and wide in total darkness, was an art form by itself. The paper had to go in dead square, otherwise somewhere after the start, the edge of the paper would start meshing with the gears, which would firstly stuff the print up, and secondly, possibly jam the processor; real problems and time waster when that happened.
If you do a search, you should find some threads regarding large prints.
For wall projection with these sizes a metal wall is best, using magnets to hold the paper up. You must remember that all of this is done in total darkness and for a print of this size two people work in complete darkness to unload a specific length of paper, cut it with a Stanley knife, then affix it to the wall in the correct position. Exposure is often up to 10 or 15 minutes with very big enlargements. Familiarity with your co-worker, was an important pre-requisite to working in the darkroom with this kind of enlarging!
The minimum negative size is 4x5" with 8x10" being preferable. By using copy internegative materials (no longer available) one could take a 35mm transparency and dupe it up to an 8x10" negative for enlargement.
From start to finish often took a minimum of three days as checks and client approval was needed at every step of the way. The process is/was so expensive, mistakes had to be kept to a minimum.
Mick.