We will describe two alternative approaches to antiquing brass. Both are straight forward but the results are quite different. Illustrated above is Ammonia Fumed Brass.
This method involves dipping clean and unlacquered brass in a proprietary antiquing solution. These solutions are a dilute mixture of acids, copper sulphate and sometimes additional chemicals to improve color consistancy and resistance to contamination.
The process is substantially the same regardless of which brand of solution is chosen. You should be sure you are dealing with solid brass as neither brass plated steel or zinc will antique predictably. The first and most important task is to thoroughly clean the brass. If the item is lacquered this coating must be removed either chemically with acetone or paint stripper or mechanically with abrasives. Modern lacquers are becoming extremely durable and the task of their removal can be the hardest part of the job. I recent years it has become easier to buy hardware in a polished but unlacquered finish, if possible you should buy this finish (usually classified as US3A, MB3A or PBA).
Wear rubber household gloves and work in a well ventilated area during the whole of the following procedure.
Prepare a dilute solution of one part antiquing solution to 10 parts room temperature water in a ceramic or plastic bowl large enough to accommodate your items. Submerge the items in the solution and agitate to remove air bubbles that would otherwise result as bright spots on the metal. You will notice the color develop in a matter of moments, at first a coppery pink that darkens through red brown and eventually a brown black. If you expect to highlight your finish you should let the darkening progress past the tone you ultimately want. If you prefer an even tone remove the item when it appears the right color.
Rinse the item under hot water and clean off the powdery residue with a sponge or a scotch-brite pad for an immediate highlighted effect. If the color is still too light simply return to the antiquing solution. If it is too dark then a scotch-brite pad will quickly take you back to clean metal and you can try again. If you are satisfied with the color then dry the item quickly and evenly, avoid leaving wet spots as these will invariably turn darker when dry.
The antiqued metal can be left as is, lacquered or waxed. If left unprotected it will continue to age, lacquering or waxing will help preserve the finish.
It is possible to turn brass to a graphite like black following the process outlined above, but you will usually need to dip the item at least twice and clean the residue off the surface between dipping. If you try to reach black in a single dipping the color will wipe off.
When brass is exposed to an atmosphere of ammonia vapor it develops a green brown oxide finish. This oxide layer is as close as you can come to a natural patina.
The following instructions will allow you to patina smaller items with relative ease, the same principals can be adapted for larger pieces.
You will need a plastic container with a tight lid. We use the white buckets sometimes called "Pickle buckets" that can easily be obtained from hardware stores, breweries and many other sources, any other well sealed plastic container will work. Cut a piece of plywood to make a shelf that will sit a few inches off the bottom. This shelf can sit on three blocks of wood to ensure it remains level. Pour a cup of full strength or "Clear Ammonia" into the bottom of the bucket, place the items for antiquing on the plywood and snap the lid in place. Full strength ammonia can be obtained from architecture offices or print shops with "blueline" facilities, "Clear Ammonia" from the grocery store. It is an extremely unpleasant fluid and should only be handled by competent adults in well ventilated areas or outside.
Depending on the temperature, humidity and freshness of your ammonia the antiquing will take minutes or hours so take the occasional look to see how it is progressing. The color will darken a little and inclusions of verdi-gris will form when the items are removed from the container. You can either leave the finish as is or wax it for a burnished effect.
If you are seriously attempting to fool anyone as to the age of the hardware and furniture you will need to mount the antiqued fitting, then wax and polish it in place. If done with some general understanding of the effects of care and aging on actual antiques the results can be very convincing.
Because the ammonia evaporates fairly quickly leaving only water you will need to replenish or replace it every so often.