What Solution for Etching sterling silver?

A. Sasha, I would try either the ferric nitrate solution or the 40 ml methanol [affil links], 10 ml hydrogen peroxide, 10 ml ammonium hydroxide solution.

A. 4 g potassium iodide
1 g iodine
40 ml deionized water (or more for more dilute etch)

This is not too harmful a solution, but stains skin purple, so wear rubber gloves ⇦this on eBay or Amazon [affil links] .

Also try
40 ml methanol,
10 ml hydrogen peroxide,
10 ml ammonium hydroxide.

The solution should be made up fresh before etching and will gradually become less and less active over a few days.

A. The concentration of the hydrogen peroxide solution is something like 30% in water. The ammonium hydroxide can be a similar concentration. You can also dilute the etch with more water if the etch rate is too fast (e.g. in thin film etching).

Another etching solution for silver is Iron (III) nitrate in water, heated to about 40 °C. The initial recipe I read quoted a saturated solution. I tried something like about 20 g in 100 ml, which is fairly dilute compared to this, and it etched the silver well.

Thank you for the information.

However, due to our security concerns in the USA, these materials are declared hazardous and will not be sent to my home site shop. Wonderful.

A. You could try a photo lithography technique. You use a light sensitive polymer called photoresist to cover your silverware (I think you can get a sprayable version) - you have to do this in a photographic room with special light. You then need a photomask, which could be either a clear acetate or a sheet of glass with the desired pattern that you require (you have regions where UV light can get through and regions where it can't). Place the photomask over the photoresist and expose to UV light. Develop the photoresist in a similar way to photographic film and you are left with patterned photoresist with exposed metal regions. You can then use the etching solution to etch the exposed metal (the photoresist will act as a barrier where you don't want etching). Rinse with water when done and then remove the photoresist with acetone ⇦this on eBay or Amazon [affil links] Warning! highly Flammable! (nail polish remover).

A. I would suggest that you could scan your photograph digitally and change its colour resolution to straight black and white (2 colours). Then print the image onto a transparency with an inkjet or laser printer. Then cover your rectangle of silver with a photoresist polymer, e.g. Shipley S1813 - this can be done by spin coating it (silver rectangle held on a rotating chuck and prior to spinning, the photoresist is spread on) - or it could be sprayed on with a sprayable version (you have to do this in a dark room, or a room where UV has been filtered out). Still in the darkroom, you then place your printed transparency over the photoresist and expose to UV light (light passes through the clear regions and exposes the photoresist). Develop the photoresist (just like photography) and you then have regions of exposed silver and regions of silver covered with photoresist. Dip the plate in a silver etching solution and leave to etch. After etching remove the photoresist with acetone ⇦this on eBay or Amazon [affil links] Warning! highly Flammable! . This might be easier to do than the technique you mention.

A. Hi,

A couple of tips concerning etching silver, which I have been struggling with for much of this year.

Electro etching will speed up the etching process, and/or allow more dilute etching solutions. It also tends to reduce undercutting of the etch, and can thus allow deeper etching.
To electro-etch, you attach the piece to be etched to the positive side of a small power supply (anode) and the negative side to a piece of stainless steel. These are then both immersed in your mordant. I use about 1.5 V and a silver ring will typically etch at around 30-100 milliamps.

For photo etching, I've been using Electrolube PRP, which comes in a spray can, and can be ordered in the UK from maplin.co.uk. However, I've just started experimenting with a photoresist film which promises to be much more robust, and last longer in the etching tank. I got this from capefearpress.com (lovely name, huh?) and it is called purtech.

A. Nice to hear about the use of the electro technique, which I had read a little about in a good reference book I have seen. I have only ever been concerned with etching very thin films that are typically less than 200 nm. Using an iron (III) nitrate solution gave the best resolution with a photoresist when etching features that consisted of 5 micron wide tracks. This was with Shipley S1813 resist that was spin coated on silicon wafers. The methanol, ammonia, hydrogen peroxide would undercut features of this width but worked well if the features were larger. In response to the question regarding the appropriate methanol solution to use, I think any of the first 4 would be okay. It is just basically methyl alcohol that I used - nothing special about it in terms of purity - anhydrous isn't important either as the ammonia ⇦this on eBay or Amazon [affil links] and hydrogen peroxide solutions have water in them anyway. The fifth solution you listed is 50% methanol and 50% water and this may not work as well as it would only contain half the amount of methanol in the recipe - you could maybe add double the amount and then have a solution that is diluted more with water.

A. I've been trying PCB Etchant Solution from Radio Shack. Contents; ferric chloride ⇦this on eBay or Amazon [affil links] . Intended for copper etching on PC boards. The bottle recommends 20 minutes in the liquid but it seems to take much longer for silver etching. Works beautifully on copper. Keep separate baths for copper and silver as copper may be deposited onto your silver.

Lisa, ferric chloride ⇦this on eBay or Amazon [affil links] is the standard etchant for copper in PCB's and big manufacturers use tanks full of the liquid for the purpose. I'm guessing that in the case of silver, there will be a displacement going on between the iron and the silver such that silver will be dissolving to produce silver chloride with iron falling out of the solution to accommodate it. There is probably a link with their respective positions in the electrochemical series.

A. You can etch sterling silver using Ferric Nitrate. Dissolve Ferric Nitrate crystals in distilled water (300 mg of Ferric Nitrate to 400 ml water). Suspend the sterling to be etch upside down in the solution and leave for anywhere from 2 - 5 hours. I tape the metal to a piece of styrofoam and float it upside down in the solution. If you can vibrate the solution, the etching is speeded up (I use a bubbler for a fish aquarium under the plastic container holding the ferric solution

I like this method because it is not as dangerous a chemical to keep in the studio. It will not burn skin, and gives off minimal fumes (I keep it under a fume hood nevertheless).

To see more information you can check teaching notes for ferric chloride ⇦this on eBay or Amazon [affil links] (for etching copper, brass and bronze) at my website www.makersgallery.com/gossetch.html) the technique is the same for either solution - the ferric nitrate just takes longer. I hope that's helpful.

A. The solution with potassium iodide and iodine will work as it is just by immersing what you want etched into it. I found that it etches silver when I tried it one day - its a common etch for gold and I tried it with some silver I was doing and it worked well though slower than with gold.

For the photo lithography process, you will need some kind of 'dark' photographic room. I imagine that the 'red' light that photographic rooms would be fine to work under. RS Components sell a photoresist aerosol solution that you could spray onto your object in the dark room and then leave to dry. You would then expose through your photomask with a light source, preferably a UV source (though I'm sure it can be done with a white light box) and the time is typically between about 5 seconds and 30 seconds depending on the power of your light. You then develop the photoresist like a photograph in photographic developer (sodium hydroxide), or RS also sell a developer product. The object is then ready to be etched in the silver etch solution. After that has been done and washed, you can strip the unwanted remaining photoresist with acetone (nail polish remover contains acetone). [Some additional notes were sent privately to Elizabeth]

A. In the days I was making jewelry, I was commissioned to do a pendant in sterling silver with words supplied by the client etched into the surface. I used Riston, a photo polymer used by the electronic industry and ferric chloride ⇦this on eBay or Amazon [affil links] . As I remember there was a whitish compound being formed, which would be silver chloride that is an insoluble white material. I was also commissioned to do a large number of small brooches with a design supplied by the client. This I duplicated unto a piece of positive film so they could be cut apart after electro-etching the design and outline of the oval brooch, using a sheet of silver. I used common salt as an electrolyte, which formed silver chloride that I was able to melt back into silver using bonami and some charcoal mixture in the crucible.

This was all done before scanner, computers and printers.