Here is my latest and best technique for aging brass. I thought that putting the buckles into a rock tumbler might be a good way to remove the lacquer and soften the look. It's slower than sandblasting (see previous post), but less harsh and more uniform.
I went to Amazon and bought this three pound capacity rock tumbler by Thumlers. It came with polishing grits, but I judged them to be too fine for what I was wanting to accomplish. I just tossed in some sand and some rocks along with the buckles, added water, and tumbled it for 20 hours. It worked beautifully.
To make the buckles look a bit beat up, I took a ball peen hammer to them (on a steel plate), giving them flat spots and dents and dings.
Next, to darken the soft gold color, and to add a little green patina, I gave the buckles a vinegar bath which just speeds up their natural oxidation. I dunked them three times, allowing them to dry in between. Each time they developed more color.
And here is the result. On the left is the original buckle as I bought it from Tandy's Leather. Next is after tumbling. The third one is after hammering. And on the right is the final look, after the vinegar bath.
Here, side by side, I present the buckle transformation showing the before and after.