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After scanning (some of) them I would like to destroy the old 35mm slides I inherited due to privacy concerns. I will separate them from the frames, so I'm talking about destroying only the thin film slices. They are from a wide range of time spanning from the early 1970s until today.

No, I do not want to keep them as a backup just in case the scanning process later turns out to be suboptimal or I lose my HD's (which is the typical answer I found on the Internet ;-).

I thought about

  • burning them
    But that could be very toxic, or isn't it? I'm talking about several thousand slides. What would happen if I put those in a campfire or similar?

  • heating them in an oven
    But again this could produce toxic gases, or won't it? And anyway, would it even work? What temperature would be needed? I'm reluctant to simply try it out because of the fear of creating toxins in my oven.

  • putting them in some chemical
    Is some household chemistry capable of destroying them to the point where the pictures aren't visible anymore?

  • cutting them into thin stripes
    But a normal shredder for paper actually creates stripes so wide that each is like a complete picture itself, so that doesn't really count as a way of destroying them. I would need to have a very fine cutter and it's not important enough to specially buy such a thing, unless it's very cheap.

Any ideas or other proposals? Maybe someone has already done this without hiring specialists for the job (which really would be overkill in my case)?

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    \$\begingroup\$ The thought of destroying the slides really makes me uncomfortable. I hope this isn't insulting: you do know that scanning technology continually improves, and that you can't do CSI-level fake analysis of poor data, right? \$\endgroup\$
    – Dan Wolfgang
    Jan 18, 2016 at 15:35
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    \$\begingroup\$ Probably not the place to ask, but why are you so keen to destroy inherited slides? Do they take up that much space? Are you sure that nobody else in your (future) family would ever want/appreciate access to them? Personally, photos (prints or slides) are something I would never destroy. \$\endgroup\$
    – osullic
    Jan 18, 2016 at 16:25
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    \$\begingroup\$ I think "how to destroy slides" is a reasonable enough question for this site; we don't need to get too much into the details of why somebody's doing this. \$\endgroup\$
    – Philip Kendall ♦
    Jan 18, 2016 at 16:43
  • \$\begingroup\$ Of course, everybody making use of the proposals in the answers below should be aware that after the process the slides are gone forever. That's the nature of destroying. @PhilipKendall is right of course, but I can disclose that much: In my case, there were lots of slides of private content involving people none of my family knew (or cared about). Also, the involved people stated to have no interest in these slides. So I just want to destroy them before dumping them to avoid issues with someone else's privacy. \$\endgroup\$
    – Alfe
    Jan 20, 2016 at 11:13
  • \$\begingroup\$ No one has mentioned recycle value of the celuloid. That's what I think of in discarding my 8000 slides. \$\endgroup\$
    – Ronald
    Mar 19, 2018 at 14:17

9 Answers 9

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Ordinary household bleach will destroy the image. The image is contained within a thin layer of gelatin. Household bleach will separate (lift off) the emulsion from the film base thus destroying the images.

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    \$\begingroup\$ That sounds promising! I will conduct some experiments with different doses and report the results here :-) \$\endgroup\$
    – Alfe
    Jan 18, 2016 at 13:06
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... a normal shredder for paper actually creates stripes so wide that each is like a complete picture itself ...

Most of the shredders you buy for home use don't cut the mustard; you want one that produces small enough pieces that the images would be useless.

There's a standard for that, called DIN 66399, that defines source materials, levels of security and maximum cut sizes. You'd want to locate a shredder that's F-2 (film, level 2) or higher. The equivalent for paper would be P-5 (paper, level 5) or higher. The requirement for both of those levels is that the shreds have an area of less than 30 mm² and the minor dimension be less than 2 mm.

Depending on where you live, you may have access to businesses that specialize in secure data destruction. These companies will have shredders that will do the job and they should be able to tell you what materials and levels they can handle. For a one-time job, this will be a lot less expensive than buying a good shredder.

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  • \$\begingroup\$ Yeah, well, as I stated, hiring professionals for my case would be overkill and probably way too expensive. Thanks for the information about the concerned standards, though! That was interesting. \$\endgroup\$
    – Alfe
    Jan 18, 2016 at 13:23
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    \$\begingroup\$ @Alfe: Call around; you may be surprised. One of the data destruction companies where I live will shred the contents of a standard sized file box for about $10. \$\endgroup\$
    – Blrfl
    Jan 18, 2016 at 15:28
  • \$\begingroup\$ Mustard seed is usually about 1 to 2 mm a seed, of course such a course shredder won't cut it! Mustard greens should shred fine. Besides, securely destroying mustard is a rare necessity. \$\endgroup\$
    – rackandboneman
    Nov 8, 2018 at 17:15
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A kitchen blender or food processor would do a pretty good job at converting the film to dust. You might add a slice of bread, some dry beans, or some other dry material to keep things moving inside the container. Used blenders are available in thrift stores for just a dollar or two if you think you wouldn't want to use the appliance for food after blending film.

Another option is to use the shredder several times. Run the film through it once, collect the shreds, and dump them into the shredder again. Depending on how much material there is, you might want to form a sort of funnel or hopper from paper or cardboard to guide the shreds onto the shredder blades. There's a limit to how small you get get the pieces with this method -- once they reach a certain size they're more likely to just fall through the shredder than to be cut up any more. But that limit may be small enough to be acceptable to you.

Abrasives offer another option. You could, for example, glue the film to a flat surface with the emulsion side (the less shiny side) facing up. A few passes with a finishing sander loaded with 80-grit sandpaper will remove the image completely, and what's left of the film substrate will be covered in hardened glue. Or, drop the slides into an old coffee can or other tough container, add a handful of sand, sharp gravel, aluminum oxide, or anything else that's abrasive. Add the cover and shake shake shake shake shake until the images are no longer visible. Then shake a while longer just to be safe.

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The safest, simplest, and cheapest way of destroying the images is to drop the slide film into boiling water.

The gelatine-bearing image layers will quickly melt, slide off the film base into a black gelatinous mass which you discard into normal household waste.

The plastic (PET) can be put into solid industrial waste although it is recyclable. Without identifying recycling identification (type 1), recycling installations will probably discard the amount you're handling informally.

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I would suggest just finding a furnace that burns waste and using that. Some dumps may have them and many office buildings and factories do.

No, I do not want to keep them as a backup just in case the scanning process later turns out to be suboptimal or I lose my HD's (which is the typical answer I found on the Internet ;-).

It's a typical answer because it's very good advice. I'm in IT and in IT we have found from experience that multiple backups are a necessity, not a luxury. Give it some thought if losing the images would be an issue.

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    \$\begingroup\$ Actually, here in Berlin, every dump gets burned in the end. I'm just reluctant to give the things away without destroying the information first. And I won't be able to throw them into the furnace myself ;-) You are right of course about the backup necessity. I would recommend to dicuss that on the superuser forum, though. \$\endgroup\$
    – Alfe
    Jan 18, 2016 at 12:58
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Depending on the quantity. If there are just one or two, just moisten the emulsion side which i. s the side facing the screen, wait for a while, scrape it with some sharp object or your finger nail will do. If the number runs to hundreds or thousands, prepare a bucket of water with washing powder, add some bleach if you like, soak the slides in it overnight or one or to days, you will indeed find the slide washed away entirely. The slide becomes clear, and all dye will go to the water and you will have a bucket of prune juice.

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Place the slides in a waste container or dumpster for your local municipality to pickup and dispose of in a landfill.

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    \$\begingroup\$ That's not a secure method for destroying slides. And I think (educated guess here) he wants to get rid of them for privacy issues. See: dumpster-diving. You wouldn't just throw an HDD in the garbage, would you? \$\endgroup\$
    – ppp
    Jan 18, 2016 at 4:01
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    \$\begingroup\$ Secure? Who said anything about that? \$\endgroup\$
    – dpollitt
    Jan 18, 2016 at 4:02
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    \$\begingroup\$ just an educated guess. That's why I didn't downvote: because it's not yet certain why he wants to destroy them but I can't think of any other reason why he doesn't simply throw them out other than privacy. \$\endgroup\$
    – ppp
    Jan 18, 2016 at 4:04
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    \$\begingroup\$ Pato is right. I'm of course concerned about privacy. Everybody should be all the time (I'm not talking about becoming paranoid, just being aware). And dumping inherited slides would simply ignore the whole topic. Besides, my question never was about getting rid of them. It was explicitly about destroying them (for whatever reason, probably to get rid of them, agreed). I will add the privacy concern nevertheless explicitly. \$\endgroup\$
    – Alfe
    Jan 18, 2016 at 12:44
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I think a standard home-use cross-cut shredder would do the job. Especially if the resultant shredding were then disposed of in varying places, making reconstruction impossible.

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You could always shred them very fine with a sufficiently sharp and sturdy knife (big chef knife would be perfect, a box cutter could do but might be difficult to safely control at the force required): Stack them (without frame!), cut fine strips off the stack, then lay bundles of strips in parallel on a cutting board and just chop them into short pieces...

Alternatively, stack them up, fix the stack very securely, then have at it with an electric drill...

Glue them all together, it is unlikely someone will bother to try and get them unstuck...

Try if you can make the base material brittle enough to be able to crush it into fragments by freezing it...

Simply dump the lot into a cheap or expired can of black paint, black epoxy resin, concrete, let the whole can dry out hard...

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  • \$\begingroup\$ Thanks for the bunch of ideas! ① Cutting them is not feasible with the amount of slides I was thinking about. ② Are you talking about drilling through them? That would leave holes in them but not shredder them completely. ③ Gluing them together actually sounds like a nice idea. You are right about that probably nobody would take such a plastic block apart. ④ I don't think they will become brittle enough by a normal household freezer but it might be worth a try. ⑤ Normally I dispose of paint rests by giving them to a special waste dump. They might object to mixtures of slides and paint ;-) \$\endgroup\$
    – Alfe
    Nov 8, 2018 at 16:52

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