Whether or not to clean a vintage knife is of hot debate in the knife collecting community. While some knives benefit from minor cleaning, any dirt or rust that will involve large-scale restoration could actually detract from the value of your collector's piece. Small dirt and rust deposits can be safely removed at home, and minor blade sharpening can also be accomplished. Follow these steps to bring out the hidden beauty of your dirty knives.
Assess the condition of your knife. Minor surface rust, dirt deposits on the handle and a slightly dulled blade edge are all problems that can be safely fixed on almost any knife. Larger areas of rust and extremely blunt blades may require a complete refinishing of the knife. This sort of refinishing could harm the value of your knife and may be best to avoid, especially if your knife is rather old. If you are unsure whether your knife should be cleaned, consult a local expert or with other knife collectors for recommendations.
Remove surface rust deposits from the blade of your knife by using the knife to chop up an onion. The juices of the onion will loosen the rust and the abrasive cutting motion will help to rub the rust loose.
Remove set-in rust by applying WD-40 or another lubricating oil. Allow the oil to sit and work on the rust and then wipe away with a cloth. Rust that will not come loose by either the onion or oil method will need to be polished away with steel wool or a grinding wheel. This will usually equate to refinishing the entire blade to ensure the surface is even and uniform after rust is removed. If you do not feel comfortable with the operation of a grinding wheel, you may want to take your knife to an expert for cleaning.
Sharpen the blade with a whet stone or sharpening leather. When sharpening, always work from the handle towards the tip of the blade. Use even, quick strokes. If your blade is exceptionally blunt, you may want to take the edge to a grinding wheel. Again, if you are uncomfortable with the use of a grinding wheel in knife sharpening, you may want to consult an expert.
Lubricate the hinges and joints of folding knives such as pocket knives. This will insure the knives open smoothly and joints will not rust shut.
To remove any other dirt or grime from a knife, boil the knife in water for 60 seconds. The heat will soften the deposits. Allow the knife to cool and then wipe clean with a soft cloth. Do not boil any knives with plastic parts, as these will melt and be destroyed by the heat of boiling.
Wipe down your knife's blade with a fine cloth after you are through cleaning and sharpening. Make sure you remove all fingerprints, grease and loose dirt. This will help keep your knife clean and rust-free for years to come.