I am a pentax too! I have 2 Super ME's, 1 x s1a and one of those modern digital things... K30!
I'll try that with the fixer to see if it works. Do you mean an 'exposed to light' small piece of film leader?
I can use the barclay paper for experiments anyway. I am a novice although I seen the original price of it and the paper was the most expensive part of the original darkroom kit (no enlarger!)