HOW TO ETCH STERLING SILVER
PART V : Etching; Housekeeping; A note on Agitation; and Disposal of Etching Solution and Neutralised Waste
1. Add tap water to the water bath (about a third full). Place your etching container in the water and turn it on. The water bath level should be at the top of the warmer once you add the ‘pot’. Top up if needed but don’t overfill. Then Place your etching solution pot into your water bath to heat up before you put your silver in. Loosen the lid; and heat to 45- 50˚ C. You can’t measure the etching solution temperature, but you can measure the water bath temperature. You can go cooler, but I would advise against hotter as it will give an aggressive etching result. On my Tommee Tippee bottle warmer, my optimum setting is just below No.2 on the dial. I heat mine up for a good hour before etching.
2. When ready, I place my prepared Silver into the solution, hanging the tape ‘arms’ holding the pieces over the top of the pot. Ensure the Silver is below the etching solution, but not so low that it’s touching the bottom of the pot. I like to hang ~1cm under the water line.
3. Make a light fold/pinch in the tape ‘arm’ so that it sits on the lip of the pot. Attach plastic garden peg(s) to the ‘arm’ on the outside of the pot to help weight it.
4. Place the lid gently on top of the pot to keep the heat and steam in.
5. Set a timer! You will need to know how long it's been in there, and may want to set alarms to remind you to check your etching regularly. I set a timer to count total time, and another for every 30-minutes for checks.
6. Check your etchings regularly! Lift them up, and you should see grey over the etching area. This is etching waste (silver sludge). You can help remove this to expose the silver underneath for further etching in a number of ways. I dip mine in and out of the pot to help ‘wash’ it away. You can lightly brush it with a feather (be careful as you don’t want to remove the resist!). You can also aid this with agitation (see section on agitation). Be careful with this process as you don’t want to remove the resist or disturb the sediment at the bottom of the pot. Keep checking and gently agitating until you’re happy with the depth. For me, with my current solution, this is after ~90-minutes I
7. Remove the mount and check in natural light to ensure you have the depth you're looking for. If it's looking good, move on to the next step which is neutralising your etch.
NB. Your timings will really vary depending on how new your solution is, and how deep you want to etch. You can get a reasonable etch within 30-minutes so experiment with a new solution. It also depends how deep you want your etch to be.
Neutralising Your Etching
1. Place the mount in a bowl of tap water with a teaspoon (or two!) of bicarbonate of Soda. Agitate the bowl with a plastic spoon for a good minute to neutralise the ferric nitrate.
2. Rinse in cold water.I
3. It’s at this stage that you can handle the Silver, and remove the pieces from the tape. Peel them off the mount. Wear gloves.
4. Remove the Silver and place in a pot of acetone, or wipe front and back with acetone if easier. I tend to etch in large batches so this way is quicker for me. The acetone will remove any remaining tape, and the resist. I have a mini mason jar of acetone that I use for resist removal. I place all pieces in it, gently swill it around for a few seconds. (The jar gets sludgy but I just top it up as and when needed. Keep it sealed and it will last quite a while.)
5. Remove the pieces from the acetone. If you have them in a pot, wear gloves or use tongs as your fingers will go a bit numb if you’re fishing about in there for 30 pieces of silver!
6. Give the pieces a wipe over with a paper towel (dip the towel in the acetone if they need a bit more help).
7. It’s at this stage that you can soft wire brush your pieces if you want. I use an old toothbrush as I don’t want to create extra filing and finishing. If you’ve neutralised well, a toothbrush should be enough.
8. Now your pieces are ready to be fabricated, soldered, set and so forth.
Once you've neutralised and cleaned your etching Silver, don't forget your Housekeeping and please be conscious of how you dispose of your waste (see next).
Then you're good to make whatever pieces of jewellery you've planned. I would advise to solder and form after etching. If you think forming will impact your design, you can form before you etch. Just take good care of protecting the areas not to etch, find a good way to hang it; and you'll do just fine.
Good luck & have fun!
Turn off your water bath.
Store your etching pot upright, with the lid securely lightened, in a dark place.
Pour your neutralising water into a dedicated pot/cat litter tub for safe disposal. DO NOT throw it down the drain.
Use a dedicated tray or board for your etching station. It will get messy.
Keep all tools you use for etching separate from other tools. Label them if it helps.
Be mindful of drips from the lid when it’s being heated. Have some paper towels to hand to wipe the lid before replacing it, as it can drip down the outside of the container into the water bath. It won’t hurt the water bath, but you could end up with it all over your hands.
Don’t forget to check your water bath water level each time you turn it on, as the water will evaporate over time and with use.
Don’t forget to turn it off when you’ve finished etching!
Label your warmers if you have more than one (I have one for pickle and one for Prips), and label your plugs!
Clean out your water bath and etching area once in a while. The stains will endure, but it’s good practice and will help these tools last longer.
A Note on Agitation
There are many ways to gently agitate your solution. It will give you a more even etch as the agitation helps etched particles fall away from the piece, allowing for the Silver behind it to be etched.
Traditionally you would ‘tickle’ the surface with a feather. You can also use a fine soft brush, and gently sweep the surface each time you check the work.
As I hang my pieces vertically, I find that a lot of the particles fall away with gravity and constant agitation isn’t needed. I simply lift and dip the pieces back into the pot a few times (using the tape arm). As I do this, I see the darker grey etching areas becoming lighter. The dipping action washes away the waste, and exposes the Silver to be etched further. It’s a good way to check your etching depth too as you do this (and also see if your resist is holding!). Be careful not to dip them back in the pot too vigorously, or too low though – keep away from that bottom sludge! Try not to stir the bottom up in any way. I ‘dip’ every 30-minutes using a timer, but may check more often.
If you’re not too distracted by other tasks while you’re etching you can tap the lid or the side of the bottle warmer to give it a little extra help. You can use a wooden spoon (or whatever you have to hand) but go gentle.
You can also create constant gentle agitation by placing your water bath on top of a small motor that vibrates, like a bubbler for an aquarium. I don’t have one of those, but my tumbler is so rickety it can provide enough movement if I run it next to my etching pot. I don’t do this very often, and honestly I haven’t seen a notable difference in my results to warrant constant agitation.
Disposal of Etching Solution & Neutralised Waste
You can neutralise Ferric Nitrate with Sodium bicarbonate, commonly known as baking soda or bicarbonate of soda. Please NEVER pour it down the drain, even when neutralised. Honestly, never! Exhausted ferric nitrate is a nasty cocktail and caustic.
You also will create caustic waste each time you etch when you neutralise your etching pieces, so please think about how you’re going to dispose of this safely. Take it to your nearest waste recycling centre that accepts hazardous waste as you would do with other workshop waste. Put it in a jam jar or pour it into a labelled tub of cheap cat litter (with a lid) and dispose of it properly.
And on a final note… please don't think you can extract the Silver particles from the waste yourself. The best you can do is to strain the solution through a coffee filter, bag it with the filter, and label it. Then send this to your local refinery with your lemel and scraps. Extraction of the silver particles should only be done by a refinery. Dispose of it responsibly or send it for refinement.