I’m thinking about growing some, possibly in a frame which I will hang on a wall. I was inspired by this artist:
Upon reading further about copper sulphate crystals, it seems they eventually dry out and turn to powder. I’m wondering what I might seal them with that will be non-reactive and wont destroy the appearance.
Blue copper sulphate is highly soluble in water. When exposed to moist air the surface absorbs water and precipitates finer crystals, which gives you a powdery white surface over time. It’s also highly poisonous. We had semi-natural formations of that in our copper mine (chalcanthite mineral.) They form nice blue stalactites in our tunnels.
Good to look at but bad in everything else. Now, if you want to preserve them, I would advise only a small piece which you can encase in a glass or clear plastic cube that’s airtight, and has a little packet of sodium hydroxide or silica gel to mop up moisture within.
Too poisonous then? Thanks. That’s probably good advice. There are no kids here to play with it, but no matter.
I was thinking to grow a “field” of them inside a box frame, and then coat them with something. I’d hang it on the wall.
I considered that I could pour polyester casting agent over it, but perhaps not: I’d end up with air bubbles and I’d have to seal the backside too.
One crystal then, in a display tube, sealed with a desiccant.
Perhaps I could do stained Alum crystals instead, or salt, though I don’t think they get very large.
Wait, I got my facts reversed. The blue crystal is the hydrate form while the white powder is the anhydrous form of copper sulfate. So the anhydrous white powder will form on the surface of the blue crystal with exposure to heat, air and light. It seems the acrylic coat will work best. Sorry 'bout that.
Thanks the_diego.
Copper sulfate is about 100 times as poisonous as table salt. I’m not sure I’d call that highly poisonous - you need to avoid licking your fingers when handling it, but it’s not the same kind of hazard as, you might encounter when, say, smelting copper, where you could be exposed to fumes (including those of other things like arsenic)
Might have gone overboard there. But it does make you sick even if you don’t ingest it. And being soluble, a lot of it is a pollution hazard.
Ok, thanks for the further information. I think I might try for a small deep framed bunch.
I’ll find a plastic bowl that can cover the frame, a sheet that can go under it, then I’ll cover the crystals with acrylic casting, and finally use a wine vacuum pump to pull a vacuum in the bow. That should draw any of the airbubbles out.
Better safe than sorry, for sure. About 3 grammes (less than a teaspoon) of the stuff, ingested, will easily see off an 175 pound human - proper care should be taken, but there’s no great danger unless it’s ingested or inhaled.
Wow-I once read (“The Good Old Days-They Were Terrible”) that food canners in pre-FDA USA added copper sulfate to keep green vegetables green! There was also a guy who marketed a copper sulfate solution to keep swimming pools clear of algae!
I work with copper and often want it to go green. Preservation wise on sheet one can use wax (Renaissance wax as used in museums) If let bare it will indeed all fall off quite quickly. I have bowls i greened a few years ago that are well preserved with a wax polish though it does change the colour slightly it darkens it.
I might add don’t colour copper then decide to rework it with the green in place then heat it with a gas torch…it makes you feel very ill!Wash it in viniger and salt first!
Copper sulfate can’t be THAT toxic; I assume the toxicity is from the copper and not some unusual chemical property of copper sulfate. Copper also isn’t toxic in the way lead or mercury is (trace amounts are needed for nutrition). As long as you don’t eat it you should be fine; I never worry about getting copper poisoning from copper wire which I regularly handle (of course, I know that solubility is a big factor; even mercury isn’t absorbed well if ingested in metallic form).
Anyway, I was going to suggest using casting resin to seal the crystals but it has already been suggested, and you actually want to keep moisture in, not out, so a sealed jar should work. Also, does it actually dry out? Plaster of Paris is hydrated calcium sulfate and doesn’t dry out (not actually the correct term, since the water is bound in the material) unless you heat it up; Wikipedia seems to say the same about copper sulfate, which should be fine as long as it doesn’t reach 145F (unless it is different from calcium sulfate, which does have a higher dehydration temperature?).
Can’t be how toxic? The LD50 for CuSO4 is 30mg/kg, compared to 3000mg/kg for sodium chloride.
That is: an 80kg adult could be expected to have a 50/50 chance of survival after ingesting either 240g of table salt, or 2.4g of copper sulphate.
(LD50 is based on studies in lab animals, but it’s a good rule of thumb for substances that are generally toxic)
It’s toxic because of the copper, but also, because it’s a soluble salt. You can’t absorb metals in their elemental form, but salts in solution are part and parcel of the way our bodies work - and the wrong salts are therefore easily introduced.
That said, I’ll stick with ‘not dangerous unless ingested or inhaled’.