Every type of metal clay suggests the use of distilled water for moistening your clay. Many metal clay users don’t understand why they should use distilled water. Many of us get away with using tap water. Why the fuss? And, what is distilled water anyway?
One of the myths regarding the use of distilled water is that it will help prevent mold in your clay. Sorry, but that is not the case. While distilled water shouldn’t contain any mold spores in it, the main source of mold spores is your local environment. Tap water, which contains some chlorine, will do more to prevent mold than distilled water! To read perhaps more than you ever wanted to know about mold and metal clay, read my post Oldy But Moldy.
Distilled water is pure water with nothing added or (supposedly) contaminating it. Of course, it is usually sold in plastic bottles, so there are probably a few contaminating molecules from the container in the water. Water is distilled by boiling it and recovering the water vapor; salts and other contaminants are left behind in the boiling chamber. It can also be made using a filtering process called reverse osmosis. Distilled water tastes “flat” because we are used to and want a few contaminants like salt in our drinking water. Carbonated beverages start with distilled water and add the drink syrup or ingredients to it. In that case, they want pure water, because any contaminants can alter the flavor of the beverage and we all know how people are about their Coke and Pepsi! Like Coke and Pepsi, you can buy it at the grocery store.
Distilled water is the best choice for adding to your metal clay, because you can be certain that you are not adding any chemicals that can affect the metal clay. Metal clays can react with contaminants such as calcium and aluminum in ways that are not desirable. Calcium and aluminum, for example, bond with pure silver and you no longer have elemental silver. The result is that the contaminated silver clay will not sinter properly. If you have “hard water” that deposits a lot of calcium (white residue) or iron (rusty residue), or if it smells sulfurous you should probably avoid using your tap water.
If you are in an area that has good tap water without a lot of contaminants, you can add tap water to your metal clays. However, if your water is not relatively pure, it may cause problems. Base metal clays may be more susceptible to contaminants because the base metals (copper, iron, nickel, and tin) are more reactive than silver. This means they will react or combine more easily with other chemicals. Gold doesn’t react with much, but at the price of gold clay, I would probably stick with distilled water when working with it!
Bottled drinking water is not the same as distilled water. It is (supposedly) high quality drinking water and usually contains at least some salts. Sometimes it is made using distilled water and adding some (sodium, potassium, or bromine) salts to the water to make it taste “good.” Bottled drinking water is not regulated, so there is no guarantee that the bottler isn’t just taking it out of the local municipal tap and calling it “mountain spring” water. Some bottled waters are taken from springs and they have whatever contaminants are present in the source water. In most cases the contaminants in bottled drinking water won’t bother your pmc, so you can use this as a second choice for moistening metal clay.
If you have a filtered water pitcher or a filter on your tap water, this can also be acceptable for use with your metal clay, but you should check to make sure that the filters are changed regularly. These filters do not remove all contaminants, and are not the perfect answer.
That said, if you add a drop of not-as-good water to your metal clay, you can probably get away with it. Just be aware that you are taking a risk and use the best quality water you can easily obtain.