The technical paper for the Ilford Rapid Fixer says that, for film, the processing time is minimum 2-5 minutes.

The question is...which is correct?

Even the technical paper of the film in question, Ilford HP5, says the same thing, but I don't know how I should regulate myself for deciding which time use.


1 Answer 1


You can easily test yourself. Cut off a snippet of film, how about using the tongue of the 35mm roll etc. Pour a small amount of the fix in a small bowl. Swish the snippet about in this fluid. The film enters opaque and quickly clears and becomes transparent. All this is performed in ordinary room light. Time how long it takes for the film to clear. Double this time to obtain the time you should allow for fixing.

By the way, over-fixing does little if any harm. It takes an hour or more for the fixer to do any harm to developed film. What happens is, the fixer begins to attack the metallic silver image (a bleaching action). 5 or 10 or 15 minutes in the fixer? No harm no foul.

  • \$\begingroup\$ It's certainly worse to under fix it, so it's better to be willing to error on the side of caution. \$\endgroup\$
    – Davidw
    Dec 31, 2019 at 4:38
  • \$\begingroup\$ Time in the fix solution is a variable based on concentration, temperature, standard vs. rapid formula etc. Time to clear is dependent on emulsion thickness, silver content, hardness of emulsion etc. Paper 45 thru 70 seconds --- film 2 thru 7 minutes (film has more than twice silver content). \$\endgroup\$ Dec 31, 2019 at 15:49
  • \$\begingroup\$ Film is viewed backlit, light makes one transit. Paper viewed by reflection, light hits paper, traverses emulsion, reflects off white backing, reflects back, again traverses emulsion. Two passes thus ½ the silver needed. \$\endgroup\$ Dec 31, 2019 at 15:55

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