Can you please help me with this..?

Good Morning.
I've searched thru the forum and that helped me a lot with understanding such as 1+19 for stock and 1:1 for dilution etc., but what I'm still not getting is if, for example, Ilford Rapid Fixer states a 1+4 stock good for between 2-5 min, what if I diluted it 1:1 or 1:3 etc. How do I figure out the times for that?

Thanks tons.
Tom

Regardless of the dilution, the proper time for fixing films is twice the time it takes to clear the film. This is why the label says 2 - 5 minutes.
Rapid fixers especially, can have bleaching effect, you probably don't want to work with a dilution stronger than what is specified by the manufacturer.

I use a rapid fix at paper strength for film, and it works just fine. Takes a little longer, but I'm not in that much of a hurry either. Twice to three times the clearing time is the perfect fixing time for film. Here's a good way to tell, and also a good way to check your fixer for potency. Take a small piece of scrap film and place 1 drop of fixer on the emulsion side. Let it sit for 30 seconds, then drop the film chip into the fixer. When you can no longer see where you placed the inital drop of fixer, you have your clearing time. Double or triple that and you're good to go. Do it with a fresh batch of fixer, and note the time. As the fixer gets used up, the clearing time will increase. When the clearing time approaches 2x the original, the fixer is nearing exhaustion and should be replace.

Now there's a little warning to go with the above advice. Different films have different clearing times. To make this test valid for fixer strength, the same type of film should be used for testing each time. To make it valid for a clearing time test, you must use the type of film you are processing.

When instructions say "2 to 5 minutes" they usually mean that one should discard the fixer when fixing time reaches 5 minutes, which means when clearing time of film reaches 2.5 minutes. Check clearing time of a scrap of film periodically.

Why worry - take the easy route

If the instructions say 1+4 for 2 to 5 mins, then why not go with the manufacturers’ good advice and dilute 1+4 and fix for 5 mins

Fixer is weird stuff, its not as effective neat (1+0) as it is 1+4

I am not a photo chemist - so I cannot explain the whys and the why-nots of the above.

I just follow the instructions - there is very little creativity to be gained in how you use fixers - but plenty of pitfalls

Martin