Ideally an old map should be in as close condition to the original as possible. If the original owner put the map aside and rarely consulted it and preserved it well the map can be in "as new" condition but such circumstances are rare. The following are some of the usual defects that occur.

1. Stains. Stains come from outside influences or might result from the aging process. Outside stains might be water, coffee or similar liquid, wax are anything that can fall on the map in the course of use. Even dust and dirt or soiled fingers can soil a map. Older paper usually is of such quality that it deteriorates only slightly with age but since about 1820 cheaper paper has been used and this can deteriorate. Browning or oxidation of the paper usually appears at the edge or along the crease where it is exposed to air. Foxing or mildew spots also occurs. A skilled paper conservator can often reduce or eliminate these problems but not always.

2. Tears. These occur through use. Large maps were often folded and are weak at the folds. Other maps were folded into a binding and often tear at the fold. Atlas maps often have a centerfold that is vulnerable to tearing. As a rule the more visible a tear is in the image the greater the problem. Again, a skilled paper conservator can often reduce or eliminate these problems.

3. Margins. It is desirable to have a margin on each side of at least a quarter inch on each side if for no other reason to enable framing to occur. Some maps were not published with such margins or they have been trimmed. Such trimming reduces value. A "false margin" can sometime be added for aesthetic or practical reasons.

4. Creases. The crease on the centerfold or other fold that occurred when the map was issued can often be flattened or reduced. If this is done and they are not obtrusive it does not affect value, as all examples of the same map would have similar creases. Other creases resulting from mishandling affect value to the extent that they interfere with he appearance of the map.

5. Backing. Maps have often been dry mounted or glued to another surface. This can often reduce value a great deal as the glue or backing can contain substances that make the map susceptible to wear, discolouration or other deterioration. A skilled paper conservator can often remove the map and reduce the side affects.

Sometime folded maps have deteriorated to such an extent that they are professionally rebacked with tissue or rice paper. This usually enhances value compared to a map that needs restoration.