Turning Scrap Copper Into Beautiful Copper Acetate Crystals

Crystals, at least those hawked by new-age practitioners for their healing or restorative powers, will probably get a well-deserved eye roll from most of the folks around here. That said, there’s no denying that crystals do hold sway over us with the almost magical power of their beauty, as with these home-grown copper acetate crystals.

The recipe for these lovely giant crystals that [Chase Lean] shares is almost too simple — just scrap copper, vinegar, and a bit of hydrogen peroxide — and just the over-the-counter strength versions of those last two. The process begins with making a saturated solution of copper acetate by dissolving the scrap copper bits in the vinegar and peroxide for a couple of days. The solution is concentrated by evaporation until copper acetate crystals start to form. Suspend a seed crystal in the saturated solution, and patience will eventually reward you with a huge, shiny blue-black crystal. [Chase] also shares tips for growing crystal clusters, which have a beauty of their own, as do dehydrated copper acetate crystals, with their milky bluish appearance.

Is there any use for these crystals? Probably not, other than their beauty and the whole coolness factor of watching nature buck its own “no straight lines” rule. And you’ll no doubt remember [Chase]’s Zelda-esque potassium ferrioxalate crystals, or even when he turned common table salt into perfect crystal cubes.

34 thoughts on “Turning Scrap Copper Into Beautiful Copper Acetate Crystals

  1. Ya, as long as you’re not growing copper sulfate crystals. Those are highly poisonous. One of the reasons I came here to check out this article was to see if anybody mentioned toxicity with copper acetate. Hmmmm.

    1. I have grown many, many copper sulfate crystals. As long as you don’t eat them or inhale the dust, there is no real danger here. The LD50 is 300 mg/kg. As a comparison, nicotine has an LD50 of about 6.5–13 mg/kg. Copper acetate clocks in at 700 mg/kg, so it’s about the same as copper sulfate. Just don’t be dumb- keep it in the pantry hidden from the kids, and you’ll be fine.

    2. Actually, copper acetate is pretty highly toxic. This is probably why the person holding the crystal in the picture is wearing a glove. It is also one of the dangerous compounds that copper can form with food and is one of the reasons that copper cookware is lined with a tin coating that needs to be periodically renewed. Consuming copper acetate really can make you very ill or kill you. Please do a materials safety data sheet (MSDS) internet search before you make it. You will find MSDSs for most chemicals posted online for free by various chemical supply companies, the United States and (in other languages) some other countries, some US state governments, and a number of universities. Usually they all have almost the same information but not necessarily in the same format. Obviously this is one of the safer chemicals unless you are careless about letting it get in your body, but exactly the same thing is true about asbestos and lead paint.

    3. Copper sulfate isn’t all that bad. It’s moderately toxic, but wine growers have dusted with it for centuries, breathing in small amounts along the way. You can buy it in any agricultural/garden store.

      LD50 is 481 mg / kg ingested in rat models.

      Anyway, it pays to be generally careful around copper salts, but none of them are really super scary. (IMO, you do your own research, have your own comfort levels.)


  2. I visited Chase Lean’s article and quite a bit down the page he mentiones that it’s mildly toxic, as in, causes skin rash when you handle it much, so just as I suspected. Swallowing cupric sulfate will kill you–it’s sold as a treatment for roots in the sewer, so we know it’s a killer–so with that in mind, don’t even accidentally ingest cupric acetate either.

    1. Copper sulfate is certainly poisonous, like many non-food items, but humans are not trees, snails or fungus. Humans are barely even mice, and drawing conclusions about human toxicity from the effect on tree roots is silly. (Unless you’re an Ent, maybe!) For years we thought mustard oil was toxic, despite centuries of people consuming it in South Asia, because it turns out it’s poisonous to rats (but not humans.) There are also things out there too that mice or rats can eat freely but that are mildly poisonous to us.

      1. While you are absolutely correct, and this is a problem that there is no easy way to solve (at least until computers actually can actually simulate the human body, which as useful as it would be I also fear as a very dangerous Pandora’s box if and when it happens) because it is obviously not ethical to give humans something that you think could be a poison just to make sure. I don’t think that any sane country even does that sort of thing with death row inmates anymore because the way that people can wind up dying or being crippled.
        However, in the specific case of copper acetate, because of the fact that humans have used copper cookware for centuries, we found out the hard way a long time ago that this chemical is very poisonous to us. The oldest reference that I happen to know of without taking the time to research the question is an English translation of the German language chemical engineering textbook (one of the first true chemical engineering textbooks ever) “Wagner’s Chemical Technology” published in 1872 and translated into English by William Crooks. I have the reprint that Lindsay Publications did when they were still in business.
        Now I would normally agree that there is a trend today to over extrapolate and decide to do nothing because you are worried about something that might possibly be a risk. I am not saying not to make or use copper acetate. I am just recommending people use proper laboratory safety precautions.
        The book mentioned above gives directions for the bulk preparation of copper acetate (at least bulk by the standards of the era) for use as a pigment known as Verdigris, and notes that both the neutral and basic acetates (a bit more in depth chemistry, resulting I think in changes to the oxidization state of the copper that they just didn’t know about then but affected the color of the pigments produced) are “highly poisonous”.
        Please bear in mind that this was a point in time when doctors still regularly prescribed Mercy compounds for oral consumption (and you can find them in this reference) and paint maid from nothing but boiled linseed oil and lead oxide was the standard (which didn’t change till after my parents were married!). So for them to actually have safety warnings kind of gets my attention.

  3. ” Is there any use for these crystals?”
    Yes, there is. Neutron spectrometers normally use massive single crystal copper slabs (a slice of a single crystal) on a neutron beam line. I have experimented with other materials, and copper acetate monohydrate single crystal gave the best result (compared to pure copper)) as neutron energy dispersion was excellent. Lead (II) Sulfide single crystal also gave a good result .

  4. Thanks for the rabbit hole Dan,

    Trying to decide if I want a Alum or Potassium crystal. (Grow more quickly with fewer steps/ingredients) However I’m sure I don’t have the room or patience right now XD

  5. I don’t know if it’s more toxic – copper acetate or copper acetate crystal!… Found! 😬
    There is the powerful poison in the middle,
    Don’t even think for a while to touch the copper acetate with your bare hands or put your hands in your mouth for no reason “It will be sure death or heavy poisoning”

  6. I grew up in the 70’s. At that time (here in Germany) copper sulphate was a completely normal part of chemistry kits for children (“Kosmos Chemiebaukasten”). Somehow I survived ;-)

    1. I think it was Cobalt Chloride that was typically the most toxic in those kits. Even so, it wasn’t super bad unless you were drinking solutions of it or licking it off your fingers.

  7. Encasing the crystal in, say, a thick glass bulb would isolate the crystal from skin contact on, say, a necklace. Def wouldn’t put that in a ring. Juny’s right in saying stuff is to be handled with safety equipment, and the page shows handling with glove-clad hands. It really really really needs to come out and put safety cautions in words, and it doesn’t do that.

  8. Copper sulfate was definitely in my chemistry set in 1968. Called bluestone commonly, we’d break it up and heat it in a test tube til it was anhydrous (H2O free) and just a white powder. Then when it had cooled we’d add water and recover the latent heat of evaporation of the contained water. It got hot as hell and we realized we had discovered a major chemical and physical principle.
    Kids today are protected from exploration to their detriment. That being said, allowing us to play with mercury and nitric acid might have been a little edgy in a lot of ways…but I’m still here…ten fingers and both eyes.

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