This is a very touchy and controversial subject. In short, if you have a rare, valuable, or classic stamp and you want to preserve its original value—the answer is «NO». The only time you should consider restoring such stamps is if they urgently require preservation, and then, only by a highly qualified professional.
Even if a stamp isn’t extremely valuable, many philatelists believe that altering a stamp in any way reduces its value and many don’t even want such stamps in their collection. For this reason, the American Philatelic Society stipulates that its members must identify a stamp that has been repaired or restored with an indelible ink mark—so that future buyers will know exactly what they are getting.
That being said, if it’s your collection, can’t you do what you want to your stamps? Well, yes! Many collectors will repair common or invaluable stamps with the purpose of making their collection more aesthetically pleasing. For example, many will refresh colors with different chemical baths, get rid of rust the same way, or wash them gently to dislodge any dirt or soiling. But if you ever decide to trade or sell one of these stamps, there would obviously be an ethical obligation to reveal these repairs to the buyer. You would also have to be prepared for the possibility of getting less money for your stamp even if it was purchased.
Obviously, a repair made with the intent to defraud buyers is completely unethical. Such repairs include adding or removing perfs, bleaching cancels or regumming. These changes are generally made to make the stamp appear to be something it is not, usually a more valuable stamp.
In conclusion, most collectors are honest however and would never defraud their fellow philatelists. But keep in mind that for many, any kind of restoration reduces the value of a stamp. So unless you just want to keep your stamps for yourself, forever and ever, it might be a good idea to not alter them.
Generally accepted restoration:
- soaking* a used stamp to remove an old hinge or to remove the stamp from an envelope
- soaking* a stamp in mild detergent to remove some soiling
- pressing a stamp to smooth out creases or folds
*in all cases of soaking stamps, collector beware: make sure your stamp hasn’t been printed using fugitive ink, otherwise you will end up with a blank piece of paper!
Controversial repairs which absolutely need to be divulged:
- adding or removing perfs to change perf measure, perfing a straight edge stamp
- filling in paper thins
- mending tears
- bleaching out of cancel to make stamp appear unused
- adding or removing of overprints
- trimming of margins to make stamp appear more centered or to change a perfed stamp to a straight edge
Keep in mind that if and when dealing with altered or repaired stamps, dealers generally know what to look for. Most repairs can be detected by using a magnifying glass, a UV lamp or a spectrometer. So look for a respected stamp dealer who will be able to keep you well informed about your purchase.