Support the Hobby -- Join the American Philatelic Society 23 Jun 2013 07:24:47pm
re: Denmark Scott 463/SG 508 colour changes
Hi Martyn,
Well, the stamps is engraved and the only color affected is an orange which prompts me to suspect oxidation as an alternate explanation. There are plenty of U.S. orange stamps that occasionally display similar darkening of the color. Use hydrogen peroxide solution which you can buy from any drugstore to clean the stamp. Apply using a Q-tip and then rinse in water. I'd be curious if that does the trick in this instance.
Arno
P.S. Not sure if Perry can still supply the missing images in the above old thread? I believe back then we did not yet have a picture upload function and with external picture hosting services pictures will unfortunately get lost over time.
Oxidation is an incorrect term since the inks are not made with metal that absorbs oxygen.
Sulfurette occurs naturally on some older stamps printed in orange, yellow, green or brown. The ink colors were created by adding a lead chromate pigment to the formula. Over time, a stamp may be exposed to sulfide pollutants and the lead chromate pigment changes to lead sulfide (black), thus the discoloration. Soaking the stamp in a 2% hydrogen peroxide solution (commonly sold for household use) reverses the chemical reaction, changes the lead sulfide to lead sulfate and returns the stamp to most of its original color. Soak the stamp for a few minutes, and then be sure to thoroughly rinse the stamp in cool or luke warm (never hot) water. Allow the stamp to dry face down on a double layer paper towel before returning it to the collection. Using this method on an unused stamp will damage the gum. Unused stamps can be treated in a sweat box, but it will take longer to work, and the humidity from the sweat box may still damage the gum.
Arno, I thought of this too, but modern stamps are rarely, if ever, printed with inks containing lead chromate. Never-the-less, I'd be interested to hear how the stamp reacted to a hydrogen peroxide bath. Can't hurt it any.
