By 
There are ways to make a good card look even better and more attractive to bidders. In doing so, an ordinary card can be elevated to super card status and become the subject of a bidding war that turns a card that cost you pennies into a three-figure multi-bid item on eBay. But you must be very careful when cleaning these fragile items or you could eliminate all resale potential.
* Postcards often get dirty when the edges have been exposed by the sides of a stack or the album containing the cards. It is very common to see a very clean postcard with a dirty margin, the margin being the only part of the article exposed to daily hazards such as dust, dirt, water, sunlight. Most of the dust can be removed with a soft rubber or a piece of dry bread.
Use a large rubber band or a large piece of bread to keep your fingers from touching the card and your fingernails from scratching or tearing the delicate paper. Hold the card very carefully at both corners closest to the dusty edge and don’t rub it too hard or the friction will cause the paper to wrinkle and wrinkle.
With an eraser or bread between the thumb and finger of the other hand, gently rub in one direction over the powdery area. Do not use back and forth strokes directly on the card, this will cause the material to tear or thin. If the dust doesn’t move, leave it alone, too much rubbing will damage the surface and affect the image and make it useless.
* Real photo postcards are often dirty or covered in fingerprints and are the easiest to clean. Real photo postcards also wrinkle quite easily, which is usually not a problem, except when dirt gets caught in the folds and makes the condition look worse than it really is. Again holding the card on a hard surface, with the index finger and thumb of one hand keeping it slightly stretched out, make gentle strokes in one direction over the soiled areas with a damp kitchen towel or facial tissue.
Make light strokes, don’t rub or you’ll leave marks and might even tear the card or rip off part of the surface. Lanolin-based facial and baby tissues are especially gentle for photo postcards and can apply a little extra pressure along the line of a dirt-encrusted fold. Do not rub against a fold line or the card will disintegrate. Don’t expect to remove all dirt, these items are very old and fragile, rubbing too hard will cause damage and reduce the value of the card.
*Most of the cards, with the exception of some printed and most actual photo types, were printed on layers of paper and were not actually made with any card at all. The top of usually three layers is the image part, the bottom is the direction part, usually with an additional layer in the middle for support.
Layers often separate at the edges, sometimes completely, usually from moisture. It is difficult, almost impossible, to re-glue layers that have completely crumbled, it takes time and skill, and the result is rarely worth it on an ordinary card.
Most household glues are thicker than those used to create the original card and give the finished card a clumpy appearance that also looks and feels too thick. Where the layers are split at the corners and the card body remains intact, you can easily apply a drop of glue between each layer, smooth it out with the nozzle of the glue bottle, then place the card on a flat, hard surface and smooth it out. gently. lightly tap repairs with a clean finger. The short stroke of the margins or the glue may seep through and your card will stick to the surface and be impossible to remove.