Interpreting HT2 test results

I recently acquired the chemicals to mix up some HT2 and have been testing the last few batches of prints that I have washed. I am following the instructions to read the area of the print discolored by the test solution after 2 minutes. It shows a very faint stain, which I understand to be okay. I then rinse the solution off the paper and hang it up to dry. I notice that after awhile the stain darkens to an unacceptable level.

My question then: is the fixer adequately removed from the paper if the stain is faint after 2 minutes but later darkens to an unacceptable level?

Dan Henderson said:

... My question then: is the fixer adequately removed from the paper if the stain is faint after 2 minutes but later darkens to an unacceptable level?

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Yes. HT2 contains light-sensitive silver nitrate! The entire test needs to be conducted under subdued tungsten light and evaluated quickly under brighter lights. After that, the light will darken the silver nitrate and the test samples are 'ruined'.