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Sometimes, after using the last full sheet of photo paper in a package, I'm left with a number of extra test strips. Is there any problem with gauging exposure with paper from a different package of photo paper, while using these leftovers?

3 Answers 3

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As long as both are the same paper emulsion (i.e. both Ilford MGRC IV) and from the same batch number this is likely to work well.

If they're the same emulsion, but different batches, there may be a significant difference in speed -- enough to make a "good" exposure a second or two too long or too short, which will cost you at least one full sheet to correct.

If they're different emulsions (for instance, MGRC III vs. MGRC IV) or different surface finish, I wouldn't even try it. Test strips are supposed to save you from wasting whole sheets printing with wrong contrast or exposure -- not trick you into wasting more.

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  • I guarantee they aren't the same batch (purchases many years apart), but where is the batch number on Ilford paper packages?
    – Davidw
    Apr 4 at 19:24
  • Honestly, I've never used Ilford paper, but I'm used to seeing it on Kodak and, many years later, Arista papers on the box label near the expiration date.
    – Zeiss Ikon
    Apr 4 at 19:25
  • Even if the packages are from the same batch, storage conditions will also after some time play a significant role. If you (or the dealer if you buy it later) has kept the new package stored coolly and the old almost empty package has been in and out of the dark room and often kept in warmer surroundings, it is quite likely that the paper in the old pack has lost sensitivity compared to the new package. In that case, a print on the new paper will be overexposed (too dark and/or too contrasty) even if the test strip is good.
    – jarnbjo
    Apr 5 at 16:27
  • @jarnbjo Notice I said "likely" to work well, not "guaranteed" to work well.
    – Zeiss Ikon
    Apr 5 at 16:29
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Leftover test strips imply that you have more test strips than you need. Implies that a pack of paper includes enough test strips (or more than enough depending on how you look at it).

This suggests that keeping them is just cluttering the darkroom.

Worse, it is clutter that is possibly out of date or a different emulsion…which would make mistakes more likely even if you were not going to be working in the dark with dim light.

Darkroom processes are better when consistent and simple. Saving old test strips is neither.

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I've done this in the past with Ilford papers and had no issues. I would recommend trying one old and one new test strip together, to make sure they produce the same result. A similar issue is making a final print from the last sheet in a box, and then wanting a second print, which needs to be taken from the next box. Again, this has worked for me when I had to do it.

On a related note: I also tried using Ilford MGRC Deluxe Glossy (RC paper) test strips for final printing on Ilford MGFB Classic Glossy (Fiber paper), and it's amazing how similar those two papers are. Starting out on RC paper saves a lot of time. I got the idea from watching people on YouTube testing this 5th generation Ilford RC paper. Note that you can't do this with the previous generation MGIV (4th generation) RC paper.

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