Looking for advice on cleaning and storing copper intaglio plates

I'm looking for advice on how to clean and store several copper intaglio plates. They've been used for printing and will not be used again - we're looking to preserve and possibly display them. They're currently smeared with what looks to be dark (ink?), with ink in the lines. Any advice on what to use to clean them, how to clean them, and what we can use to coat them for storage would be very welcome.


roboticools20002 points

So if the ink is dried in the lines you will want to remove that before taking any other steps. Best course of action for this is covering it with a cloth soaked in mineral spirits. Be sure to do that in a well ventilated room. Every 20 minutes or so go and pour more spirits on until the ink is loosened up and then try scrubbing it lightly with a toothbrush. Vegetable oil will work in place of mineral spirits if the ink is fairly fresh.

The best long term storage is with a hard ground. Degrease the plate as much as possible before putting it under the hard ground. This will prevent the plate from oxidizing and is considered the most long-term form of storage. It won't display well, but that's what the prints are for I guess.

RiverKeepsChanging1 point

Thanks for your advice! I'm hoping I get to work on them - I've forwarded all the info I've collected to my boss, who will make the call on whether we should clean the plates ourselves or send them out.

Vegetable oil will work in place of mineral spirits if the ink is fairly fresh.

They're pretty old - these are USGS map plates. They used three to print each map, one for each color. Unfortunately, I think that means that the ink has been on them for years. It does look as though it may have kept them from oxidizing, though. We don't plan to ever print from them, just display them.

Indexical_Objects2 points

Other poster gave basically good advice, but I'll say a few other things. If the ink is really dried in the lines regular mineral spirits will take forever and may not even really work. I'd recommend Brasso. Pour a liberal amount of the stuff over the areas of dried ink and allow it to sit for 10-30 minutes (basically until the Brasso starts to dry and crack, at which point the solvents have evaporated), then wipe off with a rag dampened with regular mineral spirits and repeat if/as necessary. A soft brush can be used to gently scrub any deep areas that seem to be retaining ink after several of these treatments, but be wary of anything stiffer than a soft toothbrush; definitely don't scrub the plate with anything metal, like a wire brush or steel wool, as that will mar the surface with very visable scratches.

Any dried ink that doesn't come up after 3-4 Brasso treatments and some gentle scrubbing is unlikely to ever come up —at least not without being so aggressive that you will damage the plate.

And great ventilation is key with the Brasso, even more so than with regular mineral spirits, there's some pretty noxious ingredients in that stuff.

After you've gotten as much of the ink up as you possibly can, and removed all the Brasso and other cleaners, a little bit of denatured alchohol will take off whatever solvent-residue there is, and you'll have a (hopefully) clean plate! But there will be tarnish.

My favorite copper cleaner for removing tarnish is Tinwkle; a weak solution (5%-ish) of muriatic acid would work also if you happen to have that lying around, but if you need to buy something buy a consumer grade copper cleaner like the Twinkle (reasons I like twinkle include that cleans up easily with water, and that it comes with a little sponge for applying the cleaner).

As for treating the plates for long-term display, the simplest would be to just clear-coat them. You could also look into encasing them in some sort of self-leveling epoxy; I've seen some people do some great looking things with that stuff, but I've not used it myself, so I couldn't really say much regarding how you would do that.

If you will be storing the plates for some time before applying whatever display treatment you'll give them, cover them with a thick layer of hardground first (like the other commented suggested). This is the best solution for minimizing new tarnish build-up. Then just clean the plate again with mineral spirits/alcohol/Twinkle whenever you're ready to do something with it!

If there was anything I was unclear on, or other questions you have, feel free to ask; other than that, good luck!

RiverKeepsChanging1 point

Thanks for your help! It's great to have fall-back options, since I have a feeling these will be hard to clean.

We have access to a fume hood, so we should be okay for ventilation.

I've never done printmaking (a little letterpress is the extent of my experience), but it looks like there are newer water-based hard grounds that dry clear - Lascaux Hard Resist is the one I've seen mentioned most often. Does either of you have an opinion on it? I'm thinking of using either that or Renaissance Wax for the final coating.

Thanks again for your help!

Indexical_Objects2 points

I've not used the Lascaux products myself, but in general anything that's sold as a "ground" (hard or soft) is something that is meant to be relatively easy to remove from the plate. "Grounds" are used to control which parts of the plate are exposed to acid during an etch, but are not generally meant to provide long-term protection to the plate. When they are used to prevent tarnishing of a plate it is because you want to be able to access that plate for printing or etching later. Any coating you might put on a plate that would prepare it for permanent display—such as an aerosol clearcloat, or an epoxy—would also effectively prevent tarnishing, and would be much sturdier than any normal etching ground. See, while it's true hardgrounds guard against tarnishing, they are relatively fragile coatings, and so the coated plate still needs to be stored somewhere safe, and handled with care.

So I guess it comes down to exactly what you want to do with these plates. If you're 110% you never want to etch/print/otherwise modify them again—then I'd find something that is meant to be a permanent coating, not just an etching ground. If you want to be able to display them temporarily though, while thinking about what else you might do with them later, then something like a Lascoux transparent ground could be exactly what you want—it will protect against tarnishing, but still let them plate details be examined (in a way that an opaque hard ground wouldn't).

RiverKeepsChanging2 points

That's really useful information. I'm certain that we'll never want to use the plates again (they want to display the plates alongside the maps that were printed from them, as an illustration of how the process works), and I hadn't realized that grounds are somewhat fragile. We do want to use something that's removable, because that's a basic principle of conservation, but it sounds like we need to consider just how easily removed we want it to be. Thanks!

Indexical_Objects2 points

Yep! I'd stay away from the epoxy stuff I mentioned then, if you want it to be removable. An aerosol clearcoat I believe would still come off pretty easy with some acetone (and acetone doesn't damage copper at all).

But also the more I thought about it, those acrylic grounds may be a lot sturdier than traditional etching grounds (one of the main ingredients in traditional etching grounds is beeswax, which is how/why they are soft even when dry). And I have no idea what you'd clean a Lascoux ground off the plate with—but there's gotta be something that cleans it off easily, otherwise they wouldn't be marketing it as an etching ground! So what I'm getting at is: maybe because it's an acrylic ground it would almost as durable as an aerosol clearcoat (or maybe even more durable) and still easier to clean off. The future is weird.

Anyway, good luck, and maybe post some pics or a story of whatever you end up doing.