How to get rid of the postmark on stamps?

I used to wear a postmark! There are many kinds of postmark oils, most of which can be erased, and a few can't! If you have experience, you will know if you can put it on! According to my practice, it is best to wipe it with white vinegar, that is, it can erase the postmark without hurting the stamp! Specific methods: cut the stamp from the envelope, soak it in vinegar, separate the envelope paper on the back, and then rub it gently with your hand or rubber to grasp the strength, otherwise the stamp will be useless! Soak the pasted stamps in clear water for a while, then take them out and stick them on the glass to dry. The best way is to prevent. Send a letter, stick a stamp and apply a layer of glue on the surface of the stamp, and you can handle any postmark! The recipient cuts it directly, soaks it in water, and the postmark drops without wiping it! Disclaimer: this is just my hobby, and offenders are proud!