Thursday, January 14, 2010

Non-Toxic Etching


For all of you printmakers out there, I've been doing some research on non-toxic (or much less toxic) etching techniques that I can do in my studio without needing to install an exhaust system.

I came across NontoxicPrint.com and they outlined a way to etch zinc plates (which I use) without nitric acid and the toxic fumes it emits. You can actually etch zinc, aluminum and steel in a mixture of copper sulfate, table salt and water.

So, I decided to do a test and etch a small zinc plate (6" x 3") with a 50/50 mix of copper sulfate and regular table salt (not iodized). See print above. The solution was a small amount -- 1L hot water mixed with 200ml of the powder mixture (100ml copper sulfate and 100ml salt).  I used an old plate that had hard ground on it from a long time ago and didn't bother to reground the plate before I drew into it (hence the messiness of the lines and the bitten edges from old ground flaking off). I had no idea how much time would be needed so I sectioned the plate off into 15-minute increments except for the first 10 min section.

What's interesting is that copper sediment forms at the etched areas much the same as bubbles form when the plate's in nitric acid. So you need to brush off the sediment in the same way as the bubbles. I didn't brush anything off during the etch because I wanted to see what would happen. I did, however wipe off the sediment each time I took the plate out to cover a section for the next etch. And in doing so, I inadvertently removed some of the old hard ground so there are some foul bitten areas around the marks in some areas.

For the next test I'm going to use the acrylic, waterbased ground (Z-Acryl) and see how that holds up to this process. It looks like this process etches in about the same time as nitric acid and there are no harmful fumes in the air during etching. So an exhaust system isn't necessary and (yay) I can etch in my studio fume-free.  The solution is considered a marine pollutant as it is toxic to water wildlife and needs to be disposed of properly (NOT down the drain), yet according to NontoxicPrint.com:
The left over copper residues from the etching process are a valuable resource. You may well be able to find a local recycling firm that actually pays for your etching residues - a substantial part of these is solid copper. Or, with the addition of sodium bisulfate to the etching residue you may actually be able to reclaim the solution a number of times.
So, there you have it. No more need to handle deadly nitric acid when there's a much safer way to etch. And NontoxicPrint.com has recipes for solutions to etch copper and brass as well (amongst other non-toxic printmaking techniques).

UPDATE: I've updated the links for nontoxicprint.com since one wasn't working at all and the others didn't direct to the relevant page.

NOTE: There is a comment below from an anonymous commenter who explains a chemical reaction between copper-sulfate and salt. Since I have no chemistry background, I cannot verify whether or not this information is accurate. However, please note that there is always a risk involved in using and mixing chemicals that you are not familiar with. Please use caution and get as much information before-hand when using all etching methods whether they are considered traditional or "non-toxic." I find that nontoxicprint.comZea Mays, and others are good resources to look into for comprehensive information on non-toxic etching as well as other "greener" printmaking materials and techniques. 

5 comments:

Carol's Original Prints said...

Hi I read your experiments with copper sulphate and zinc and aluminium. We moved to this method a few years ago. In Horsley Printmakers studio we have ferric chloride for copper and aluminium for the copper sulphate. I prefer the latter but there is a downside to the spent solution and residue. You have to have sufficient space to allow the residue to settle so you can deal with the solution and the residue separately.
Difficult after a workshop as our space is limited. I like to speed with which it etches which really keeps you on your toes.

spiderink said...

Thanks for your insights. I am really happy to hear from someone who has used this process.

How do you separate the residue from the solution? Pour off the liquid and let the residue dry?

I'd love to hear more.

Suzanna McMahan said...

Can this be used on Brass Bronze or Copper?

Elana Goren said...

For copper and brass, you use a ferric chloride Edinburgh Etch. See this article on nontoxicprint.com

Anonymous said...

It might be dangerous to add salt to copper sulphate--apparently it is if you are using electro-etch--was reading on www. greenart.com :

" Some of these reactions can be found when adding salt to copper sulphate to create 'Saline sulphate etch' , which may then be used electrolytically in the Galv-On process. Free copper deposit produced by etching zinc plates in saline sulphate etch forms a 'zinc copper couple' generating a current and producing chlorine and caustic soda. Free chlorine and hydrogen gas in a confined space like a covered etching tray can form an explosive mixture. If the chlorine gas is not channelled and collected, but mixes freely with the caustic soda, then sodium chlorate is produced . Sodium chlorate is a very toxic chemical banned since 2008 in the European Union where it was used as a powerful weed killer."