Brass and other metals are easy to protect with a durable clear lacquer coating so long as care is taken in four critical areas, application, cleanliness, temperature and contamination.
Cleanliness means no residue of older finishes, no greases and no dust. Acetone is a good general purpose cleaner/degreaser. You can lacquer over a polished or clean antique finish. Temperature should be around 65 degrees though some latitude is acceptable here, below 50 and above 90 will probably cause difficulties. The item to be lacquered should be at the same approximate temperature. Contamination of the freshly sprayed surface seems to be the hardest hurdle to overcome for most people. The lacquer we sell will set in just a few minutes to the point where dust will not become imbedded. It is vital to reduce exposure to dust for this brief period.
Application of lacquer from a spray can is easily mastered after some basic concepts are understood. The goal is to cover the surface evenly with a coat of finish that flows together to form a film. If the spray can is held too far from the object insufficient finish will fall on the surface and the individual droplets of lacquer will not flow together. If the spray can is held too close to the object an over heavy coat will result and drips or sags will be the certain consequence. 8 inches is a suitable starting point.
Critical to a good spray finish is the right lighting. A low light either from a window or a bulb reflecting off the surface will tell you all you need to know about the quality of your work. With a little experiment it is easy to find a suitable light source in almost any situation.
To coat an object evenly will invariably require more than one pass with the spray can. Each pass must be smooth and slightly overlap the previous one. Each pass must start off to one side and progress over the object and finish off the other side at which point you must release the spray head. Releasing the spray head is a vital habit that allows the valve to clear itself of lacquer build-up. I would recommend a maximum of 2 seconds per pass, preferably less. If possible you should hold the item in your hand and rotate it to provide access and good raked lighting to all sides without delay. If you have to set the item on a surface to spray it you must make absolutely sure the surface is dust free all around. The air pressure from the spray will stir up any dust and spread it evenly on your otherwise perfect finish.
The crucial moments are those after the item is sprayed. If allowed to dry in peace your finish will probably be of professional standard. Unfortunately people are inclined to fuss over the finish at this point and as often as not ruin it. Any movement near the item stirs the air and with it the dust that we do not want in the finish, movement should be kept to a minimum. Anything done above the object will shower it with dust particles so well intentioned attempts to cover with boxes to keep dust off will in all likelihood achieve the opposite. The best plan is to immediately hang the item on a nail or hook so the most important face is held vertically or up side down and leave the room. Drips, unless very bad, should be ignored at this point, they will be far less obvious when the lacquer has dried.
After investing this much effort it makes sense to handle the lacquered item with care. Do not for example let a lacquered knob roll around on a table top or throw it in a box with others unless you want to repeat the whole process.
We regularly achieve excellent results following the above guidelines in a decidedly dust-free workshop.