There has been a lot of panicky talk going around in various circles about “Pickle”. Lately, on some of the forums, there has been some very scary and potentially dangerous information given out. I will try to clarify some of the questions which have been sent to me about these statements and also about my ongoing series on soldering which appears in Lapidary Journal Jewelry Artist.
Back in the middle ages, the most widely used solution for removing copper oxides from metal was alum. This is also what cucumbers are soaking in to make “pickles” like we eat. It was probably some medieval jeweler, who, as a joke, called the alum solution for removing copper oxides “pickle”, and the joke is still around hundreds of years later.
Later on, a sulphuric acid /water solution was found to work better. Unfortunately, not everyone knew how to appropriately use /mix the solution, and there were undoubtably some severe burns and numerous other unfortunate accidents which occurred. For us modern day jewelers, there are several brand name products which are much safer and produce pretty good to excellent results. They are a buffered solution of sulphuric acid. In chemspeak, it is NaHSO4, commonly called sodium bisulfate. This won’t eat your skin off if accidentally splashed on you, but it will make holes in your clothing which will show up when your clothes are washed. To confuse the issue, sodium bisulfate is also used in food production in soft drinks and salad dressings and in preserving meat. However, more confusion comes when jewelers say they use a dry form of “sulphuric acid” as a pickle. This causes undue panic among some people who don’t understand exactly what sodium bisulfate is.
Some of the safer and more earth friendly pickles are sour salts, used in Eastern European cooking and available from gourmet stores. You can also use citric acid, or lemon juice with vinegar. Yes, vinegar is a mild acid. These tend to take a lot longer to work. Today we have several dry, granular commercial pickles available, such as RioPickle, available from RioGrande, or one called Citrex which is citric pickle, or Sparex #2. (Opinion: I don’t like Sparex #2 because of the nasty skin which appears on the water, and it’s hard to see into the pickle pot with the brownish solution.) I use PHDown, which is available at your local pool supply store and is used to regulate the PH balance of water in swimming pools and hot tubs. It’s much cheaper, almost half the price of jewelry store pickle, and is the same exact thing, (sodium bisulfate) as your higher priced commercial pickles. It will last a long time when stored as dry granules. In fact, many jewelry supply stores just sell pickle in white plastic containers with a generic “Pickle” label, and it’s just PhDown that they buy in a 5 (or more) gallon size and put it in their own containers.
Mixing pickle isn’t exactly rocket science. In a small crock pot, (I like the 1.5 quart size available at big box stores) put 4 cups of water, and about 3/4 cup of dry pickle. It doesn’t have to be exact. Always add the pickle to the water. Mix with copper tongs, and let it sit on the “Low” setting until the crystals dissolve. Pickle works best when it is warm, but not boiling. As your pickle gets used, it will turn a beautiful blue green color. (Think of the verdigris color of outside copper faucets….its about the same color) That means that the pickle is working. It does not mean it is instantly disintegrating your silver, nor copper plating your pieces. (Both of these statements have been put out on recent forums.) Your pickle will still work as it turns blue/green. I change my pickle when it gets too dark to see my jewelry laying on the bottom of the pot. Sometimes its been 6 months or more between changes. It still works. There are some instances which call for new pickle, but for general soldering clean-up, blueish/green pickle works just fine.
Have you ever heard jewelers speak of “superpickle?” Superpickle is regular pickle to which you add 1 cup of hydrogen peroxide, H2O2. It works best with a batch of new pickle. This will boost the cleaning properties of the sodium bisulfate for about an hour, and then the H2O2 will give up its oxygen atom and become H2O. In no way does it harm your pickle. Continue using the same solution as usual. You may want superpickle to extra clean sterling before you keum boo, or if you get a copper oxide (a copper “blush”) on brass due to overheating.
If you accidentally leave your piece in the pickle for a long time, like overnight, it will usually be OK. Leaving it in for a month or so is not a good thing, and you may find pitted solder joints or pits in your silver. (If you put silver in nitric acid for a month or so until it dissolves, you will have silver nitrate, which will turn your skin blue, but makes a great pottery glaze!) Always place your pieces into the pickle after quenching in water first, with copper tongs, and retrieve them with copper tongs. That’s another long chemistry lesson, so just trust me on this one. You may also use plastic or bamboo tongs.
If you accidently leave your pickle pot on for a long time, all the water will evaporate. Blue/green crystals appear on the inside of the pot,. I just start over with new pickle. The crystalized pickle stuff gets yucky if you just add water. If your pickle has evaporated, but still has water and no crystallization has occured, just add more water. It’s fine to do that. To dispose of my pickle, I merely add 4 cups of tap water and water my rose bushes with it. My acid loving plants love it. It’s like a fertilizer for them. You can also neutralize it with 1/2 cup of baking soda and pour it down your drain or toilet.
Does this help? Please email me or reply with any questions. Don’t panic that pickle is ACID! There’s been enough panic about this going around recently. Acids are all around us and we use them daily. Just use some common sense.