Thanks for the reply!
Quite interesting...I have never heard about it before and initially thought that you try to pull a joke on me, but...upon google'ing a bit I found a few sites that mention it as well.
I might give it a try, but I have no pets to go after with a cup so...I really have to take a pee over the items myself?!?!
Oh my...

It's true that the pee'n will work. However, you need to get all that chrome coating off of the knobs first. I'm also wondering what is underneath the chrome. Is it brass? If so, then the pee will work. You may also find some antiquing solutions that work on copper/brass alloys at Home Depot or Lowe's. Again, the chrome has to be removed before anything will take to the metal surface. Removal can be with mechanical abrasion or heat. If you use heat, you will need to get the surface hot enough to melt/burn the chrome coating. An acetylene torch will do the trick. But be careful not to melt the knob!

Hey QuiQue!
Thanks for the reply!
Well, actually I want the chrome to stay on.
Those knobs are made out of brass - some of those guitars have been played heavily since the 1950's and the knobs have scratches and dings all over and the chrome is still intact but dull and has (as you can see in the photos) dark grub in its recesses.
That's what I want to create.
Btw...concerning the antiquing solution at Home Depot or Lowe's...I'm located in Germany and we don't have them around.
But I can get any chemicals and mix some stuff up.
Any recomendations for a home-made antiquing solution or green patina that will stick on the knobs?
I have heard that some people use the fumes of muriatic acid to get the shine off the chrome without damaging it too much. I was hoping for a safer household applience, though.

You got me lostheart! Chrome is naturally a corrosion inhibitor. So trying to create patinas, which are in essence corrosion chemicals, are not going to work. Maybe someone else can chime in with some advice.

Hmmm...see, I never thought that it would be such a problem to create patina on something 'made to prevent corrosion'!
Not hard to tell by now that I have no clue about metal, huh?
Maybe some of the talent of you good people will rub off on me or at least inspire me to look further into this field.

Anyways...what I noticed (and I only noticed after you mentioned chrome's qualities) is that the green goo is only in the areas where the chrome is worn away!
So I guess I need to take some of it off in between the knobs fine knurling and use something to react with the exposed brass...

The green grub in the cracks was created by the acid on the skin eating through the chrome and attacking the brass. Yes chrome can be etched or even rubbed away.
If you want to play with chemicals to make your own patinas here you go:
http://www.sciencecompany.com/patinas/patinaformulas.htm

Or you may just want to try using some acrylic paints (like painters use on canvases) and make a color you want. Rub in end and remove the excess.

If I had to make some fake antique guitar knobs like that, I'd start out with new ones like you have, then put them in a tumbler with a handful of small nails or screws. Tumble them until the chrome is pretty much beaten off, then put in a weak solution of ammonia and water. Tumble some more and then bury in a box of damp sawdust while still wet. Keep warm for a week or so. Remove, put back in the tumbler, this time with a few glass marbles and tumble a little while longer. You should have nice, used-looking knobs with the requisite dents, dings and cruddy cracks, and a nice soft, "used a lot" surface finish.

It might take experimenting with tumbling media and time, and with the best solution for the patination. Copper sulfate will turn the brass green right away, but may be too bluish. I think the ammonia will do what you want, but I haven't tried faking any antique guitar knobs lately, either. Your mileage may vary, of course.

Many thanks...sounds great!
Looks like I gettin' somewhere!
Now the tumbling part is something I am not entirely sure of.
The scratches and dings are made via the nails and screws...and the glass marbles polish the knobs somewhat again? Or what are they for?
Do you put all the items in a plastic bag and tie it together before they are going into the tumbeler?
I guess this part can also be achieved via hand, can it?
I'm saying this to expand my tumblers life span!
;-)

Hey there!
That link is golden! Already bookmarked for further reference....many thanks for it!

Okay so here is what most people do (for guitars). Say you have your piece of metal, well, first you need to ding it up and scratch off areas of chrome. Then what you do is fill a container with a small amount Muriatic Acid and hang your knob a few inches above the Muriatic Acid. Lastly cover the whole contraption with a towl so the fumes stay inside the container. Check on it after a few minutes and then ever hour or so until it is aged to your liking. This is the best way to do it. I'm pretty sure that is what fender does.
-Matt

1. Get a thick plastic container, at least 12" x 12" inches square with a flat plastic lid.
2. Drill small holes in the lid, spaced a couple inches apart.
3. Get a bottle of Muratic acid. This is sold at all home depot supply type stores.
4. Get a nice respirator with good vapor filters and a place with lot's of ventilation cos' it stinks!
5. Pour 1 or 2 inches of muratic acid in the bottom of the container and cover with the lid.
6. Arrange the hardware on top of the lid, without any parts touching, screws touching are OK.
7. Cover entire bucket tightly with black plastic trash bag.
8. Leave overnight for aging and check in the morning to see how things are progressing.

You can pull a part out and wipe off to see how the aging is going. Make sure you use nice rubber gloves. Leave in longer if more aging is desired.

When the parts are done, pull them out and rinse off with soapy water. Make sure you oil any moving parts, like the bridge pieces,screws and tuners otherwise they might freeze up.

Wow.Thanks very much for the education in aging metal guitar parts. You seem very knowledgeable in this field? Do you know how to age the Plastic parts like control knobs and scratchplates?
Kind regards Chris. christopher.cross@sky.com

You could start by tumbling the chrome with rocks and/or sand them. When the brass shows through you can use aging solutions.

DULL BLACK ON BRASS: Dissolve copper scraps in concentrated nitric acid (caustic) dilute with half water. Dip the hardware in the solution until you get the color you like, then remove and rinse with water.

GREEN PATINA ON BRASS: Mix 3 oz Cream of Tarter, 1 oz Ammonium Chloride, 7.5 ozCopper Nitrate, and 3 oz Table Salt with 13 ounces of boiling water. Apply with a sponge applicator, Q-tip, or a sponge on a stick. After you get the color you like, rinse and dry.

It's best to seal with lacquer to prevent further aging.
If you can get your hands on the book; WORKSHOP FORMULAS, TIPS & DATA by KENNETH M. SWEZEY it's full of great formulas.

Regards,
Craig

uhmm..im just 14 years old..and i need help about the age of metal in the Prehistory.. its may assignment...ty

Haven't tried this, but it might take the shine off the chrome. It is similar chemically to other suggestions...

US patent 4,370,197
Process for etching chrome

An etch solution is prepared by dissolving about 50 ml. of concentrated sulphuric acid (i.e. about 98% concentration) and about 20 g. of thiourea in about 1 liter of water.

Wear gloves, respirator, safety glasses, etc. and "do as you otta, add acid to water" slowly..

Please keep in mind that when you etch chrome, plate chrome, or remove chrome by electro-chemical methods, you are probably creating hexavalent chromium, a known and dangerous carcinogen and toxin. Read up on all the proper safety measures!

Rich

Suspend chrome parts in muriatic acid fumes, not directly in the acid. Make sure parts are clean and grease free as a finger print can not allow that part to age. Leave in for about 30 mins until a nice chalky, maybe greenish fuzz builds up. Take out and leave to dry out overnight. Rinse and you should get a nice pitted result.

Jerry Garcia had to have all of his hardware gold plated for the same reason. A cheaper solution might be to wash your hands in baking soda before playing and then cleaning your guitar with an oil based polish after.