A pretty good recipe for brass cleaner, used by clock makers, is:
1 gal. water
4 oz. ammonia (26%)
4 oz. acetone
2 oz. oleic acid

This must be rinsed off and dried with a blast of air. It would also help if you could heat the article to get the remaining solution to evaporate out of the carvings.

This type of formula leaves a tarnish-preventing coat of oil on the piece, so do not polish it off after cleaning.
Casey

Where would one find the acetone and oleic acid?
Thanks.

Acetone is sold in almost any paint store, for thinning lacquers, etc. Oleic acid is harder to come by, but maybe try a welding supply. Here's a link for it.
Casey

Here is a link that might be useful: oleic acid page

Wouldn't these be covers to hide the fireplace opening in summer? Or are they firebacks? I too have coal f/p's but I don't think they would burn if the fronts were covered - probably smoke like crazy - so I doubt if they aided in heating. In fact, one of my fenders is unpierced brass & taller than usual & I can't use it if I have a fire going because it will smoke.

The covering is in two parts. The first part is a cast grill that sets on the hearth below the coal grate. The ornate cover then sets on top of this and covers the firebox. Sized appropriately to the opening.
The fireplaces were sealed off prior to my purchasing the home. I did find a source for ventless coal gas logs. I may install these into two of them.

Sounds intriguing; I'd love to see a photo if it's not too much trouble.

No trouble. I will have my son take a picture or two. Give you a better idea what I have. May not be for a day or two.

I'll look forward to seeing it. The covers that I've seen are usually missing parts & were made of thin steel so it will be interesting to see one that's in original form & condition.

Here's a pic I found on photobucket of what I think fenestrationman has:

The bottom picture is similar to the ones I'm familiar with although they usually aren't as ornate & are missing the fret?/fender?/cast piece at the bottom. In fact, I have one of these bottom pieces that I use in front of a gas log & it completely hides all of the 'guts'. But mine is cast iron & I've never come across a cover made of bronze or brass, although many have been painted gold.

The lower picture is more along the lines of what I have. I will hopefully post the pictures tonight or tomorrow. How does one post pictures? I can be technologically challenged at times.
On another note. On the lower picture, the surrounding green/brown tile work is near, if not identical to one of mine. Where is that firplace located?
Thanks.

To post a pic, you must upload your photo to an online site such as Photobucket.com. Copy the assigned HTML code & insert it into your GW message. That way it will appear on your post like the above photos. If you do a search (at the bottom of this page) for 'photo instructions', I'm sure you'll get more detailed info than what I just gave.

One of my Greek Revival fireplaces had been "Victorianized" around the turn of the century & someone had installed this green/brown tile - maybe a little less brown - believe me when I say it looks much better with an age appropriate mantle than a Greek Revival one, LOL! Mine is in central VA.

I found both of those on photobucket, and since they were set as "public" I could access the html code needed to post them. I used "coal grate" and "coal fireplace" as the search terms, and a few dozen pictures came up.
Ain't it cool?
Casey