Of f Topic Short-Wave Radio Maintenance Question

Er . . . no offense but the information here is too vague to recommend any course of action . . . there are two issues.

First, what is the component being described, and what is the symptom that you're trying to fix? If it's an air-variable capacitor (cylindrical group of tiny plates moving in and out of each other), then they aren't silver (they're aluminum), and if it's scratchy when turned it's most likely caused by the copper grounding spring on the shaft, not the plates themselves (which shouldn't touch each other at all). I guess it could be a roller inductor . . . but these are usually found in transmitting equipment and antenna tuners, not receiving equipment.

Second, silver oxide (i.e. tarnish) is an excellent electrical conductor . . . this is one of the reasons why silver is the traditional plating material for mil-spec. RF connectors and contacts. So even if what you're talking about is a roller inductor or silver-plated contactor, the presence of tarnish doesn't mean that it's a likely source of whatever problem you're having.

The best thing to do would be to get the make and model of your friend's radio, as well as the problem that he/she is having with it, and post this information to one of the many internet forums that specialize in shortwave and amateur radio interests.

Thank you both very much; I'll see he gets this info!

an electronic spray cleaning wash might work well for this.
Read the instructions on the can; some are not plastic-safe so you have to be careful where the solvent lands in that case. The spray can tip typically has a hole for attaching a straw (such as a can of WD-40). Actually WD-40 might even work but probably shouldn't use that it's messy and the oily residue attracts dust.
Use a cleaner solvent *without* any oil (some are oil based) for the same reason.
Radio Shack might have what you need or try an auto supply store. Electronics supply houses carries these products in many forms.
In any case do not use anything abrasive.

If he can disconnect completely the silver parts, he can do as follows:

Get a pan of hot water, some aluminum foil, and some baking soda. Dissolve baking soda in water. Place aluminum foil and silver parts in the solution. This is a way to remove tarnish without removing the silver.

If this is not possible, about the only other ideas are to carefully sand the dirty contacts with the 600 grit or higher sandpaper, then if possible, re-'tin' the parts if small enough with silver solder.

Here's a url on the instructions for cleaning silver:
http://www.demesne.info/Homeowner-Q-and-A/Household-Tips/Cleaning/Cleaning-Silver.htm