A few weeks ago I wrote an article giving a few resources for cold connections, which is metal working without using soldering. You use some sort of fastener instead of heat to join pieces of metal. I know many artists and crafters that are afraid of the torch, but still work with metal.
Well, after writing that article, I received a few emails about adding color to metal so I thought that would be the next metalworking topic I would tackle. When talking about 'coloring' metal, most often what the artist or crafter wants to achieve is to add a patina to the metal.
Ever notice the cool green or blue color that appears on copper or brass over time? Well, it's the natural process of the metal reacting to oxygen. The patina forms to protect the metal from further oxidation.
Using a chemical process, it's possible to add a hue ranging from green to blue to brown to different types of metals - without waiting for Mother Nature to do the work.
Even if you aren't experienced in metalworking or jewelry making, you are probably familiar with sterling silver that deliberately doesn't have a bright reflective surface (don't confuse this with the tarnish that develops if you don't take proper care of the sterling silver). Well, this effect is obtained by the metal artist using a chemical such as heated potassium suphide or liver of sulfur.
Like using a torch, oxidizing metal is not an arts and crafts skill that you just pick up and start doing. Working with chemicals requires taking safety precautions. You gotta figure that any vapor coming from a chemical reaction that changes the color of metal is probably not all that great to be breathing in - or coming in contact with your skin!
Beginners Guide to Oxidation Brass and Copper
You may have read about crafters using cat litter for oxidation. Well, cat litter or saw dust can be used for oxidizing metal, but you also need to add an oxidizing liquid to the mix.
One of the more benign recipes you can use requires mixing salt, water and plan old household ammonia. Requiring plenty of good ventilation, even with this recipe I recommend you wear an appropriate vapor mask and gloves. After taking appropriate safety precautions, combine 1/8 cup of salt, 1 1/4 cup of ammonia and roughly 3 cups of water in a glass container that can be tightly sealed. Buy a canning jar or just completely wash out an empty jelly or vegetable jar after you've finished the contents.
Moisten some cat litter - don't get it too wet or soggy - in an airtight plastic container and bury your metal in the kitty litter. Put scraps of the metal near the top of the mix for checking and when you are happy with the patina remove your metal.
To fix the patina, you'll have to apply Renaissance wax or spray acrylic. Otherwise the patina will rub off the metal.
A great resource for metal working and patina is Metals Technic by Tim McCreight, which may be available at your local library (that's where I originally found it). This book written in 1997 stands the test of time as a great resource for metal artists. It's also available on Amazon for under $20. And sorry, it's not available for Kindle but it is a Prime selection so if you are a Prime member you get free shipping and two-day delivery.